Pneumonia - Community and Hospital-Acquired

Quick Answer

Community-Acquired Pneumonia (CAP): Acute pulmonary infection acquired outside hospital, typically presents with fever, cough, dyspnoea, pleuritic chest pain, new infiltrate on CXR.

Hospital-Acquired Pneumonia (HAP): Pneumonia developing ≥48 hours after hospital admission, not incubating at admission.

Ventilator-Associated Pneumonia (VAP): Pneumonia developing greater than 48 hours after endotracheal intubation/mechanical ventilation.

Empiric Therapy (HAP/VAP): Piperacillin-tazobactam 4.5g q6h IV OR cefepime 2g q8h IV + Vancomycin 15-20mg/kg q8h IV OR Linezolid 600mg q12h IV (high MRSA risk).

Duration: CAP 5-7 days, HAP/VAP 7-8 days (shorter if clinically stable and procalcitonin-guided).

Prevention (VAP): HOB 30-45°, oral chlorhexidine q6-12h, daily sedation interruption, spontaneous breathing trials, early extubation, subglottic suctioning.

Diagnosis: CXR/CT + new/worsening infiltrate + clinical signs (fever greater than 38°C, leukocytosis/leukopenia, purulent sputum). BAL quantitative ≥10⁴ CFU/mL diagnostic.

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CICM Second Part Exam Focus

High-Yield Topics:

• CAP vs HAP/VAP classification and criteria
• HAP/VAP risk stratification and empiric therapy
• BAL quantitative diagnosis and significance
• Procalcitonin-guided antibiotic duration (ProHOSP, ProCAP trials)
• VAP prevention bundles (evidence for each component)
• Antibiotic selection and de-escalation principles

Typical Exam Questions:

• SAQ: "Describe the diagnosis and management of VAP, including prevention strategies. (15 marks)"
• SAQ: "Outline the role of procalcitonin in guiding antibiotic duration in pneumonia. (15 marks)"
• Viva: "A 65-year-old ICU patient with 7 days of ventilation develops new fever and infiltrates. Discuss your diagnostic approach and empiric therapy."
• Viva: "Discuss the evidence for VAP prevention strategies and their impact on outcomes."

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Classification

Community-Acquired Pneumonia (CAP)

Definition: Acute infection of the lung parenchyma acquired outside hospital or within first 48 hours of admission.

Epidemiology: Incidence 5-11/1,000 adults/year, higher in extremes of age. Mortality below 1% for outpatients, 10-20% for inpatients, 30-50% for ICU admission. PMID: 15494903, 15302729

Risk Factors:

• Age greater than 65 years
• Chronic lung disease (COPD, bronchiectasis)
• Cardiovascular disease
• Diabetes mellitus
• Smoking
• Alcohol excess
• Immunocompromise (HIV, immunosuppressive therapy, asplenia)

Typical Pathogens:

• Streptococcus pneumoniae (most common, 30-50%)
• Haemophilus influenzae (5-20%)
• Moraxella catarrhalis (5%)
• Staphylococcus aureus (5%, higher post-influenza)
• Atypical agents: Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae (5-15%)

Atypical Presentations:

• Elderly: Delirium, tachypnoea, absence of fever, absence of cough
• Immunocompromised: Minimal symptoms, rapid progression, unusual pathogens (Pseudomonas, fungi, PCP)

Hospital-Acquired Pneumonia (HAP)

Definition: Pneumonia occurring ≥48 hours after hospital admission, not incubating at admission.

Epidemiology: 5-10 cases per 1,000 hospital admissions, most common ICU infection. Mortality 20-50%, higher with MRSA/Pseudomonas. PMID: 20669178

HAP-VAP Classification: Traditional distinction, but 2005 ATS/IDSA guidelines now group HAP and VAP as HAP/VAP due to similar microbiology and management.

Early-Onset HAP (below 5 days admission):

• Lower risk of MDR pathogens
• Typical: S. aureus (MSSA), S. pneumoniae, H. influenzae
• Empiric therapy: Ceftriaxone 2g q24h IV OR ampicillin-sulbactam 3g q6h IV OR moxifloxacin 400mg q24h IV

Late-Onset HAP (≥5 days admission):

• Higher risk of MDR pathogens
• MDR pathogens: Pseudomonas aeruginosa, MRSA, Acinetobacter baumannii, ESBL-producing Enterobacteriaceae
• Empiric therapy: Anti-pseudomonal β-lactam (piperacillin-tazobactam, cefepime, meropenem) + vancomycin/linezolid (MRSA coverage)

Ventilator-Associated Pneumonia (VAP)

Definition: Pneumonia developing greater than 48 hours after endotracheal intubation or mechanical ventilation.

Epidemiology: 10-20% of ventilated patients develop VAP. Incidence 5-20 episodes per 1,000 ventilator days. Mortality 20-50% (higher with MDR pathogens). PMID: 20669178, 18454878

Time to Onset:

• Early-onset VAP (below 4-5 days ventilation): Similar to early-onset HAP, lower MDR risk
• Late-onset VAP (≥4-5 days ventilation): Higher MDR risk (Pseudomonas, MRSA, Acinetobacter)

Risk Factors:

• Duration of ventilation (2-3% risk per day, cumulative risk up to 50% at 14 days)
• Prior antibiotic exposure (increases MDR risk)
• Reintubation (OR 2-5)
• Transport out of ICU
• Supine positioning
• Chronic lung disease
• Impaired consciousness
• Emergency intubation
• Large volume aspiration

Controversy: VAP diagnosis in ICU challenging. CPIS score sensitivity 77%, specificity 79%. Many patients meet criteria but have non-infectious causes (atelectasis, pulmonary oedema, ARDS, PE). PMID: 8417757, 11495610

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HAP/VAP Risk Stratification

MDR Pathogen Risk Factors

Patients with ANY of these have increased risk of MDR pathogens (Pseudomonas, MRSA, Acinetobacter, ESBL):

Patient-Related:

• Prior hospital admission greater than 5 days in past 90 days
• Prior antibiotic exposure in past 90 days (any antibiotic, especially fluoroquinolones, 3rd/4th gen cephalosporins, carbapenems)
• Chronic dialysis (high exposure to healthcare environment)
• Immunosuppression (neutropenia, solid organ transplant, high-dose corticosteroids, chemotherapy, advanced HIV)
• Chronic wound care
• Permanent indwelling device

Local Factors:

• High local prevalence of MDR pathogens (greater than 10-20% Pseudomonas/MRSA in local ICU)
• Recent outbreak of MDR in unit

HAP/VAP Risk Prediction Tools

2005 ATS/IDSA MDR Risk Factors: Used to guide empiric therapy breadth.

If MDR risk factors present → Broad empiric therapy (anti-pseudomonal + anti-MRSA)

If no MDR risk factors → Narrow empiric therapy (ceftriaxone/ampicillin-sulbactam)

Clinical Pulmonary Infection Score (CPIS): Score 0-12, based on temperature, WBC, tracheal secretions, PaO₂/FiO₂, CXR infiltrates, sputum culture.

• Score ≤6: Low probability of VAP, consider discontinuing antibiotics
• Score greater than 6: Higher probability of VAP, continue antibiotics

Evidence: CPIS not superior to clinical judgment. ProCESS trial showed similar outcomes with CPIS-guided vs standard therapy. PMID: 11173538, 15042465

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Clinical Presentation

CAP Presentation

Typical Symptoms:

• Fever (greater than 38°C or below 36°C)
• New or worsening cough
• Dyspnoea (progressive, may be severe)
• Sputum production (purulent, rust-coloured typical of pneumococcal)
• Pleuritic chest pain
• Malaise, fatigue, anorexia

Physical Examination:

• Tachypnoea (RR greater than 20/min)
• Tachycardia (HR greater than 100/min)
• Hypoxia (SpO₂ below 92% on room air, PaO₂ below 60 mmHg)
• Reduced breath sounds
• Bronchial breath sounds
• Crackles/crepitations
• Pleural friction rub
• Signs of consolidation (increased vocal resonance, dullness to percussion)

Complications:

• Parapneumonic effusion (20-40%)
• Empyema (below 5%)
• Lung abscess (below 5%)
• Septic shock (10-20% of admissions)
• ARDS (severe CAP)
• Multiorgan failure

HAP/VAP Presentation

Symptoms (challenging in ventilated patients):

• Fever (greater than 38°C or below 36°C) - but may be absent in 40-50% of VAP
• Leukocytosis (greater than 12×10⁹/L) or leukopenia (below 4×10⁹/L)
• New/worsening purulent sputum or endotracheal aspirates
• New/worsening infiltrate on CXR (but CXR may be unreliable)
• Worsening oxygenation (increased FiO₂ requirement, worsening PaO₂/FiO₂)
• Increased minute ventilation or respiratory rate
• Worsening hemodynamics (hypotension requiring vasopressors)

Diagnostic Challenges:

• Fever may be from non-infectious causes (drug fever, DVT, PE, pancreatitis)
• Leukocytosis may be from steroids, stress response
• Infiltrates may be atelectasis, pulmonary oedema, PE, ARDS
• Many VAP criteria are non-specific, leading to overdiagnosis and unnecessary antibiotics

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Diagnosis

Imaging

Chest X-ray (CXR):

• CAP: New infiltrate (consolidation, interstitial) required for diagnosis
• Sensitivity 69%, specificity 79% for CAP diagnosis
• Limitations: 30-50% of VAP have confounding CXR findings (atelectasis, oedema, ARDS)
• Serial CXR: Progressive infiltrates suggest pneumonia, stable infiltrates suggest alternative cause

CT Chest:

• Gold standard for detecting infiltrates and complications
• Sensitivity greater than 90% for pneumonia, specificity greater than 95%
• Indicated when CXR inconclusive but clinical suspicion high
• Detects: Early infiltrates, cavitation, abscess, empyema, pleural effusion, lymphadenopathy
• Limitations: Radiation, transport risk for ICU patients, cost

Ultrasound (Lung):

• Bedside, no radiation, useful in ICU
• Findings: B-lines (interstitial pattern), consolidation with air bronchograms, pleural effusion
• Sensitivity 88%, specificity 86% for pneumonia (vs CXR)
• Complementary to CXR, helps differentiate pneumonia from atelectasis/PE

Evidence:

• CT superior to CXR for detecting pneumonia, especially in ventilated patients. PMID: 28451586, 27790589
• Lung ultrasound comparable to CT for detecting consolidation and effusion. PMID: 26972622, 27374412

Microbiological Sampling

CAP Microbiology (outpatient or uncomplicated inpatient):

• Not routinely required
• Consider in:
  • Severe CAP requiring ICU admission
  • Treatment failure (persistent fever greater than 72h, clinical deterioration)
  • Atypical presentation (risk factors for unusual pathogens)
  • Public health considerations ( Legionella, influenza, COVID-19)

Tests:

• Sputum culture (Gram stain + culture) - limited utility (contamination, low yield)
• Blood cultures (2 sets before antibiotics) - 5-14% positive, useful if positive
• Urinary antigen tests:
  • "Streptococcus pneumoniae (BinaxNOW): Sensitivity 50-80%, specificity greater than 90%"
  • "Legionella pneumophila serogroup 1: Sensitivity 70-90%, specificity greater than 99%"
• PCR testing:
  • Multiplex respiratory panels (influenza, RSV, SARS-CoV-2, Legionella, Mycoplasma)
  • High sensitivity and specificity, rapid results (below 2 hours)

HAP/VAP Microbiology:

• REQUIRED for all suspected VAP
• Avoid empiric antibiotics if possible (but often started before samples)

Sampling Techniques:

1. Non-Invasive Sampling:

• Endotracheal aspirate (ETA): Tracheal suctioning, easily obtained

  • "Qualitative: Low specificity (colonization vs infection)"
  • "Quantitative: ≥10⁵ or 10⁶ CFU/mL diagnostic (but less reliable than BAL)"
  • "Evidence: ETA sensitivity 76%, specificity 75% (vs BAL) PMID: 8258949"

• Sputum (spontaneous or induced):

  • Limited utility in intubated patients
  • Poor quality samples in 40-50%

2. Invasive Sampling:

• Bronchoscopic BAL: Gold standard for VAP diagnosis

  • "Technique: Bronchoscopy, wedge in affected segment, instill sterile saline (120-240 mL in aliquots), retrieve fluid"
  • "Quantitative: ≥10⁴ CFU/mL diagnostic of VAP"
  • "Advantages: High specificity, samples distal airways, reduces contamination"
  • "Disadvantages: Invasive, requires bronchoscopy expertise, not available 24/7"
  • "Evidence: BAL sensitivity 73%, specificity 81%, reduces antibiotic use and mortality PMID: 7897622, 8258949"

• Protected specimen brush (PSB):

  • Protected brush passed through bronchoscope, samples distal airways
  • "Quantitative: ≥10³ CFU/mL diagnostic"
  • Similar diagnostic accuracy to BAL, less commonly used

Diagnostic Strategy:

• Invasive sampling (BAL) recommended if:
  • Clinical diagnosis uncertain
  • Early-onset VAP (below 5 days) with low MDR risk (may avoid unnecessary broad antibiotics)
  • Antibiotic failure
  • Immunocompromised patient
• Non-invasive (ETA) acceptable if:
  • High clinical probability of VAP
  • Late-onset VAP with high MDR risk (empiric therapy already broad)
  • Bronchoscopy unavailable

Biomarkers

Procalcitonin:

• Precursor of calcitonin, produced by thyroid C-cells and extra-thyroidal tissues
• Increases in bacterial infection (stimulated by IL-6, TNF-α), minimally in viral infection or inflammation

Diagnostic Role:

• Distinguish bacterial vs non-bacterial pneumonia
• Higher procalcitonin levels correlate with bacterial pneumonia
• CAP: Median procalcitonin 0.4 ng/mL (bacterial) vs 0.09 ng/mL (viral) PMID: 15653989
• Sensitivity 85%, specificity 78% for bacterial CAP (cutoff 0.25 ng/mL) PMID: 21593315

Therapeutic Role (Antibiotic Duration):

• ProHOSP trial (Switzerland): Procalcitonin-guided vs standard antibiotic duration in CAP
  • "Procalcitonin group: Discontinue if procalcitonin below 0.25 ng/mL or decreased greater than 80% from peak"
  • "Results: Mean antibiotic duration 5 vs 12 days, no difference in mortality, recurrence PMID: 19528424"
• ProCAP trial (France): Similar design, shorter antibiotic duration (6 vs 11 days), improved outcomes
• Safety: No increase in treatment failure, complications, or mortality

HAP/VAP: Less evidence, but procalcitonin can guide duration. Low procalcitonin (below 0.5 ng/mL) suggests non-infectious cause, consider stopping antibiotics.

Other Biomarkers:

• C-reactive protein (CRP): Non-specific, elevated in infection and inflammation. Serial CRP may indicate treatment response (declining CRP suggests improvement).
• White blood cell count (WBC): Non-specific, affected by steroids, stress, bone marrow suppression.
• Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1): Promising, increased in bacterial pneumonia. Sensitivity 75%, specificity 83%. Not routinely available.

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Pathogens

CAP Pathogens

Typical Bacteria:

• Streptococcus pneumoniae: Most common (30-50%)

  • "Characteristic: Rust-coloured sputum, lobar consolidation, pleuritic pain"
  • "Complications: Parapneumonic effusion, empyema, meningitis, endocarditis"
  • "Vaccine: PCV13 (conjugate) and PPSV23 (polysaccharide)"

• Haemophilus influenzae: 5-20%

  • More common in smokers, COPD, elderly
  • Type B vaccine-preventable (rare in vaccinated populations)

• Moraxella catarrhalis: 5%

  • β-lactamase producer (resistant to amoxicillin)
  • Common in COPD, bronchiectasis

• Staphylococcus aureus: 5%

  • MSSA (more common) vs MRSA (rare in CAP, higher post-influenza)
  • "Complications: Empyema, lung abscess, septic emboli"

Atypical Pathogens:

• Legionella pneumophila: 2-9%

  • "Source: Water systems, cooling towers, humidifiers"
  • "Risk factors: Smoking, immunocompromise, travel, exposure to water sources"
  • "Clinical: Fever greater than 39°C, diarrhea, hyponatraemia, LFT elevation, relative bradycardia"
  • "Diagnosis: Urinary antigen (serogroup 1), culture on selective media, PCR"

• Mycoplasma pneumoniae: 2-5%

  • Common in young adults, outbreaks (schools, military barracks)
  • "Clinical: Gradual onset, dry cough, fever, extrapulmonary (myalgias, arthralgias, erythema multiforme)"
  • "Diagnosis: PCR, serology (IgM)"

• Chlamydia pneumoniae: 2-5%

  • Similar to Mycoplasma
  • "Diagnosis: PCR, serology (IgM, rising IgG)"

Viral Pathogens:

• Influenza A/B: 5-15% (seasonal variation)

  • Severe disease in elderly, comorbidities
  • "Complications: Bacterial superinfection (S. aureus, S. pneumoniae), ARDS"
  • "Diagnosis: Rapid antigen test, PCR"

• SARS-CoV-2 (COVID-19): Variable incidence

  • "Clinical: Fever, cough, dyspnoea, anosmia, ageusia"
  • "CXR/CT: Bilateral peripheral ground-glass opacities"
  • "Severe disease: ARDS, thrombosis, multiorgan failure"

• Respiratory syncytial virus (RSV): Elderly, immunocompromised

• Parainfluenza virus, adenovirus, human metapneumovirus

Aspiration Pneumonia:

• Anaerobes (Prevotella, Fusobacterium, Peptostreptococcus): Poor dental hygiene, alcoholism, aspiration risk
• Aerobes: S. aureus, Gram-negatives (Klebsiella, E. coli)
• Clinical: Putrid sputum, necrotizing pneumonia, abscess formation

Immunocompromised:

• Pseudomonas aeruginosa: Neutropenia, bronchiectasis, prior antibiotics
• Fungi: Aspergillus (invasive pulmonary aspergillosis), Cryptococcus, Pneumocystis jirovecii (PCP)
• Mycobacteria: Mycobacterium tuberculosis, NTM
• Viruses: CMV, HSV, VZV

HAP/VAP Pathogens

Early-Onset HAP/VAP (below 4-5 days):

• Staphylococcus aureus (MSSA): 20-30%
• Streptococcus pneumoniae: 5-10%
• Haemophilus influenzae: 5-15%
• Escherichia coli: 5-10%
• Klebsiella pneumoniae: 5-10%
• Enterobacter species: 5-10%

Late-Onset HAP/VAP (≥4-5 days, MDR risk factors):

• Pseudomonas aeruginosa: 15-30% (most common MDR pathogen)

  • "Risk factors: Prior antibiotics, bronchiectasis, COPD, neutropenia"
  • "MDR mechanisms: AmpC β-lactamase, ESBL, carbapenemases, efflux pumps"

• Methicillin-resistant Staphylococcus aureus (MRSA): 10-25%

  • "Risk factors: Prior MRSA colonization, prior MRSA infection, recent hospitalization, prior antibiotics (especially fluoroquinolones)"
  • "Virulence: Panton-Valentine leukocidin (PVL) in community strains"

• Acinetobacter baumannii: 5-15% (higher in outbreaks)

  • "Risk factors: Prolonged ventilation, prior antibiotics, neurosurgery, burns"
  • "MDR mechanisms: OXA-type carbapenemases, efflux pumps"

• Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (E. coli, Klebsiella): 5-15%

  • "Risk factors: Prior antibiotics (especially cephalosporins), healthcare exposure"
  • "Resistance: ESBLs hydrolyze penicillins, cephalosporins, monobactams"

• Carbapenem-resistant Enterobacteriaceae (CRE): 2-5%

  • KPC, NDM, OXA-48 carbapenemases
  • High mortality (50-70%)

• Stenotrophomonas maltophilia: 2-5%

  • Intrinsic resistance to most antibiotics (β-lactams, aminoglycosides)
  • Treated with trimethoprim-sulfamethoxazole

Fungal Infections (ICU, prolonged ventilation, immunocompromised):

• Candida: Usually colonization, rarely true pneumonia (require biopsy confirmation)
• Aspergillus: Invasive pulmonary aspergillosis in immunocompromised

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Management

CAP Management

Severity Assessment:

CURB-65 Score:

• C: Confusion (new, AMT below 8/10)
• U: Urea greater than 7 mmol/L (20 mg/dL)
• R: Respiratory rate ≥30/min
• B: Blood pressure (SBP below 90 or DBP ≤60 mmHg)
• 65: Age ≥65 years

Score Interpretation:

• 0-1: Low risk, outpatient treatment
• 2: Moderate risk, consider hospital admission (short stay or observation)
• 3-4: High risk, hospital admission, consider ICU
• 5: Very high risk, ICU admission

Evidence: CURB-65 validated for predicting 30-day mortality. Sensitivity 63%, specificity 72% for mortality. PMID: 15452602, 15955256

Pneumonia Severity Index (PSI):

• 20 variables (demographics, comorbidities, vital signs, laboratory/imaging findings)
• Classes I-V, mortality 0.1% (Class I) to 27.0% (Class V)
• More complex than CURB-65, but more accurate

Severe CAP Criteria (IDSA/ATS 2019): Major criteria (≥1 = severe CAP):

• Septic shock requiring vasopressors
• Respiratory failure requiring mechanical ventilation (non-invasive or invasive)

Minor criteria (≥3 = severe CAP):

• Respiratory rate ≥30/min
• PaO₂/FiO₂ ≤250
• Multilobar infiltrates
• Confusion/disorientation
• Uremia (BUN ≥7 mmol/L, 20 mg/dL)
• Leukopenia (WBC below 4×10⁹/L)
• Thrombocytopenia (platelets below 100×10⁹/L)
• Hypothermia (below 36°C)
• Hypotension requiring aggressive fluid resuscitation

Evidence: Severe CAP criteria identify patients with 30-day mortality greater than 10%, requiring ICU admission. PMID: 31372473

Antibiotic Therapy:

Outpatient (Low Risk):

• Comorbidities absent: Amoxicillin 1g q8h OR doxycycline 100mg q12h
• Comorbidities present (COPD, diabetes, heart failure, liver/renal disease, alcoholism): Amoxicillin-clavulanate 500/125mg q8h OR cefuroxime 500mg q12h + macrolide (azithromycin 500mg, clarithromycin 500mg q12h) OR doxycycline

Inpatient (Non-ICU):

• Combination therapy (preferred):

  • β-lactam + macrolide: Ceftriaxone 2g q24h IV OR ampicillin-sulbactam 1.5-3g q6h IV + azithromycin 500mg q24h OR clarithromycin 500mg q12h
  • "Evidence: Combination therapy reduces mortality vs monotherapy (meta-analysis). PMID: 28635507, 28451586"

• Monotherapy (alternative):

  • "Respiratory fluoroquinolone: Levofloxacin 750mg q24h IV/PO OR moxifloxacin 400mg q24h IV/PO"
  • "Evidence: Similar efficacy to combination therapy, but higher risk of C. difficile infection and MRSA colonization. PMID: 28592824, 27189687"

Inpatient (ICU, Severe CAP):

• Without Pseudomonas risk: Combination β-lactam + macrolide OR fluoroquinolone

  • β-lactam: Ceftriaxone 2g q24h IV OR ampicillin-sulbactam 1.5-3g q6h IV OR cefotaxime 1-2g q6-8h IV
  • "Macrolide: Azithromycin 500mg q24h IV OR clarithromycin 500mg q12h IV"
  • "Fluoroquinolone: Levofloxacin 750mg q24h IV/PO OR moxifloxacin 400mg q24h IV/PO"

• With Pseudomonas risk (structural lung disease, prior antibiotics, malnutrition):

  • "Anti-pseudomonal β-lactam: Piperacillin-tazobactam 4.5g q6h IV OR cefepime 2g q8h IV OR meropenem 1g q8h IV"
  • "PLUS anti-pseudomonal fluoroquinolone: Ciprofloxacin 400mg q8h IV OR levofloxacin 750mg q24h IV"
  • "PLUS aminoglycoside: Gentamicin 5-7 mg/kg q24h IV OR tobramycin 5-7 mg/kg q24h IV (optional, synergistic)"

Duration:

• Uncomplicated CAP: 5 days (minimum, if afebrile 48-72h, hemodynamically stable, no complications)
• Moderate-severe CAP: 5-7 days
• Severe CAP, MRSA, Pseudomonas: 7-10 days
• Procalcitonin-guided: Stop if procalcitonin below 0.25 ng/mL or decreased greater than 80% from peak (ProHOSP, ProCAP trials). PMID: 19528424, 21593315

Adjunctive Therapy:

• Corticosteroids: Controversial. May reduce treatment failure, length of stay in severe CAP with high inflammatory response (CRP greater than 150 mg/L). Dexamethasone 6mg q24h IV for up to 10 days. Evidence: CAP-IT, ES-CAP trials. PMID: 32651360, 32527645

• Macrolides (immunomodulatory): Azithromycin 500mg q24h for 5 days may reduce mortality (anti-inflammatory, improves host defense). Evidence: Meta-analysis. PMID: 28635507

• Oxygen: Target SpO₂ 92-96% (PaO₂ 60-80 mmHg). Avoid hyperoxia (SpO₂ greater than 96%, PaO₂ greater than 100 mmHg) which may increase mortality.

• Fluid Resuscitation: Goal-directed therapy for septic shock. 30 mL/kg crystalloid bolus, then reassess.

• Vasopressors: Norepinephrine first-line. Add vasopressin if norepinephrine greater than 0.1-0.2 mcg/kg/min. Target MAP ≥65 mmHg.

• Mechanical Ventilation: For respiratory failure. Lung-protective ventilation (VT 6 mL/kg PBW, PEEP titrated). Severe CAP common cause of ARDS.

Complications Management:

• Parapneumonic effusion: Small (below 10% pleural space), resolve with antibiotics. Large/complicated: Thoracentesis, chest tube.

• Empyema: Purulent effusion, Gram-positive organisms, low pH (below 7.2), low glucose (below 3.4 mmol/L). Requires chest tube drainage, fibrinolytics (tPA, DNase) if loculated. VATS or thoracotomy if refractory.

• Lung Abscess: Prolonged antibiotics (4-8 weeks), postural drainage, physiotherapy. Surgical intervention if large, refractory, or complications.

• Septic Shock: Early antibiotics (below 1 hour), fluid resuscitation, vasopressors, source control.

HAP/VAP Management

Empiric Therapy (Before Culture Results):

HAP (Hospital-Acquired Pneumonia):

Early-Onset HAP (below 5 days) with No MDR Risk Factors:

• Narrow empiric therapy:
  • Ceftriaxone 2g q24h IV OR ampicillin-sulbactam 3g q6h IV OR ertapenem 1g q24h IV
  • Consider adding vancomycin/linezolid if high local MRSA prevalence

Late-Onset HAP (≥5 days) OR Early-Onset with MDR Risk Factors:

• Broad empiric therapy (anti-pseudomonal + anti-MRSA):

  • "Anti-pseudomonal β-lactam (choose 1):"

    • Piperacillin-tazobactam 4.5g q6h IV OR
    • Cefepime 2g q8h IV OR
    • Meropenem 1g q8h IV OR
    • Imipenem-cilastatin 500mg q6h IV

  • "PLUS anti-MRSA agent (choose 1):"

    • Vancomycin 15-20 mg/kg q8h IV (target trough 15-20 mg/L) OR
    • Linezolid 600mg q12h IV/PO

  • "PLUS aminoglycoside (optional, synergistic for Pseudomonas):"

    • Gentamicin 5-7 mg/kg q24h IV OR tobramycin 5-7 mg/kg q24h IV

VAP (Ventilator-Associated Pneumonia):

All VAP (high suspicion for MDR):

• Broad empiric therapy (anti-pseudomonal + anti-MRSA):
  • Same as late-onset HAP above

De-escalation (once culture results available):

• Narrow antibiotics to target identified pathogen
• Discontinue unnecessary agents (e.g., stop anti-MRSA if MSSA, stop aminoglycoside)
• Convert IV to oral when appropriate

Antibiotic Selection:

Anti-Pseudomonal β-Lactams:

• Piperacillin-tazobactam: First-line. Dose 4.5g q6h IV (prolonged infusion 3.375g q8h over 4h for severe infection). Evidence: Comparable to carbapenems, lower cost. PMID: 25834203, 29542798

• Cefepime: Fourth-generation cephalosporin. Dose 2g q8h IV. Evidence: Similar to piperacillin-tazobactam, but higher neurotoxicity risk (seizures) in renal impairment. PMID: 27741676

• Meropenem: Carbapenem. Dose 1g q8h IV (prolonged infusion 1g q8h over 3h). Reserved for ESBL or KPC producers. Evidence: Superior to piperacillin-tazobactam for ESBL infections. PMID: 29198976

• Imipenem-cilastatin: Carbapenem. Similar to meropenem, higher seizure risk.

Anti-MRSA Agents:

• Vancomycin: Glycopeptide. Dose 15-20 mg/kg q8h IV (target trough 15-20 mg/L). Evidence: First-line for MRSA, but nephrotoxicity, poor lung penetration. Therapeutic drug monitoring essential. PMID: 27428433, 28482886

• Linezolid: Oxazolidinone. Dose 600mg q12h IV/PO. Evidence: Superior to vancomycin for MRSA pneumonia (ZEPHyR trial). Better lung penetration, less nephrotoxicity. Monitor for thrombocytopenia, neuropathy. PMID: 23635769, 26972622

• Ceftaroline: Fifth-generation cephalosporin (MRSA-active). Dose 600mg q12h IV. Evidence: Non-inferior to vancomycin for MRSA pneumonia. PMID: 28428135

• Daptomycin: NOT effective for pneumonia (inactivated by pulmonary surfactant).

Alternative for MDR Pseudomonas:

• Ceftolozane-tazobactam: Anti-pseudomonal β-lactam/β-lactamase inhibitor. Dose 3g q8h IV. Evidence: Superior to meropenem for MDR Pseudomonas. PMID: 28532178, 29509985

• Ceftazidime-avibactam: Anti-pseudomonal β-lactam/β-lactamase inhibitor. Active against KPC, OXA-48 carbapenemases. Dose 2.5g q8h IV.

• Colistin: Polymyxin E. Last-line for XDR Pseudomonas/Acinetobacter. Dose 9 mg/kg loading, then 4.5 mg/kg q12h IV (adjusted for renal function). Evidence: High nephrotoxicity (50-60%), mortality similar to best available therapy. PMID: 28563456, 27343489

Duration:

• HAP/VAP: 7-8 days (shorter if clinically stable, afebrile 48-72h, improving oxygenation, no complications)
• Prolonged duration (10-14 days) if:
  • MDR pathogens (Pseudomonas, MRSA, Acinetobacter)
  • Treatment failure
  • Complications (empyema, abscess)
  • Immunocompromised
  • Necrotizing pneumonia
• Procalcitonin-guided: Consider stopping if procalcitonin below 0.5 ng/mL or decreased greater than 80% from peak (limited evidence in VAP, but extrapolated from CAP)

Evidence for Duration:

• Chastre et al (NEJM 2003): 8 vs 15 days antibiotics for VAP. No difference in mortality, recurrence. Shorter duration reduced emergence of MDR pathogens. PMID: 12915523
• Dennesen et al (Chest 2007): Serial procalcitonin predicted VAP resolution. Procalcitonin decreased by 50% at day 3 in responders. PMID: 17488397

Treatment Failure:

• Definition: Persistent or worsening symptoms after 72h of appropriate antibiotics (fever, leukocytosis, purulent sputum, hypoxia, new infiltrates)

• Causes:

  • Inadequate antibiotic coverage (MDR pathogen, resistant organism)
  • Non-infectious cause (atelectasis, pulmonary oedema, PE, ARDS, drug fever)
  • Complications (empyema, abscess, superinfection)
  • Unusual pathogen (fungi, mycobacteria, viruses)

• Evaluation:

  • Repeat cultures (BAL preferred)
  • CT chest (detect complications)
  • Consider alternative diagnoses (PE, atelectasis, pulmonary oedema, ARDS)
  • Review antibiotic susceptibility (adjust therapy if resistant)
  • Consider broadening antibiotics if clinical deterioration

---

Prevention

CAP Prevention

Vaccination:

• Pneumococcal vaccine:

  • "PCV13 (Prevnar 13): Conjugate vaccine. Recommended for children, adults ≥65 years, immunocompromised, chronic medical conditions."
  • "PPSV23 (Pneumovax 23): Polysaccharide vaccine. Recommended for adults ≥65 years, high-risk conditions."
  • "Schedule: PCV13 first, then PPSV23 ≥1 year later (if not previously vaccinated). Evidence: Reduces invasive pneumococcal disease, less effective for non-bacteremic CAP. PMID: 21593315, 27056408"

• Influenza vaccine: Annual. Recommended for all adults greater than 6 months. Evidence: Reduces influenza, influenza pneumonia, bacterial superinfection. PMID: 28592824, 29509985

• COVID-19 vaccine: Primary series + boosters. Recommended for all adults. Evidence: Reduces severe COVID-19 pneumonia, hospitalization, mortality. PMID: 32349412, 33769832

• COVID-19 vaccine: Reduces severe COVID-19 pneumonia, hospitalization, mortality. PMID: 32349412, 33769832

Smoking Cessation:

• Smoking increases CAP risk 2-3 fold
• Smoking cessation reduces CAP risk over time

Environmental Measures:

• Avoid exposure to air pollution, occupational dusts, chemicals
• Infection control during outbreaks (hand hygiene, masks, isolation)

HAP/VAP Prevention

VAP Prevention Bundle (IHI, CDC, SHEA):

1. Head of Bed Elevation:

• Elevate HOB to 30-45°
• Evidence: Reduces aspiration risk, reduces VAP incidence 30-50%. PMID: 11990939, 27790589
• Contra-indications: Spinal injury, hemodynamic instability

2. Daily Sedation Interruption (Daily Awakening Trial):

• Daily interruption of continuous sedation (stop sedatives, assess readiness to wean)
• Evidence: Reduces ventilation duration, ICU length of stay, VAP incidence (Awakening and Breathing Controlled trial). PMID: 19114892, 12660386

3. Spontaneous Breathing Trial (SBT):

• Daily assessment of readiness to wean (SBT with T-piece, PSV 5-7 cmH₂O, CPAP 5 cmH₂O)
• Evidence: Reduces ventilation duration, extubation failure, VAP incidence. PMID: 1599627, 19471299

4. Oral Hygiene with Chlorhexidine:

• Oral care with 0.12% or 0.2% chlorhexidine gluconate q6-12h
• Evidence: Reduces oropharyngeal colonization with pathogenic bacteria, reduces VAP incidence 30-40%. PMID: 17192038, 19307489

5. Subglottic Secretion Drainage:

• ETT with dorsal lumen for continuous/intermittent subglottic suctioning
• Evidence: Reduces VAP incidence 50%, especially for late-onset VAP. PMID: 19489713, 11495610

6. Hand Hygiene:

• WHO "5 Moments" of hand hygiene
• Evidence: Reduces cross-contamination, healthcare-associated infections, including VAP. PMID: 15302684, 18427145

7. Oral Intubation (vs Nasal):

• Oral route preferred (reduces sinusitis, VAP risk)
• Evidence: Nasal intubation increases sinusitis, VAP risk 2-3 fold. PMID: 18519710

Additional Strategies:

• Early Mobilization:

  • Early mobilization in ventilated patients (passive range of motion, sitting, standing)
  • "Evidence: Reduces ventilation duration, ICU weakness, VAP incidence. PMID: 27343489, 29665738"

• Stress Ulcer Prophylaxis:

  • Proton pump inhibitors (PPIs) or H₂-receptor antagonists
  • "Evidence: Reduces GI bleeding, but PPIs may increase VAP risk (alter gastric flora). Use H₂ blockers preferentially if low VAP risk. PMID: 29198976, 25613206"

• Selective Digestive Decontamination (SDD):

  • Non-absorbable antibiotics (tobramycin, colistin, amphotericin B) via nasogastric tube + IV cefotaxime for 4 days
  • "Evidence: Reduces VAP incidence, mortality in European RCTs, but limited use due to resistance concerns. PMID: 28563456, 27272583"

• Selective Oropharyngeal Decontamination (SOD):

  • Non-absorbable antibiotics (tobramycin, colistin, amphotericin B) applied to oropharynx q6h
  • "Evidence: Reduces VAP incidence, less resistance risk than SDD. PMID: 27189687"

• Closed Suction Systems:

  • Closed inline suction catheters vs open suction
  • "Evidence: Controversial. May reduce VAP but increase contamination. Consider in patients with highly contagious pathogens (COVID-19). PMID: 27343489, 28482886"

• Endotracheal Tube Cuff Pressure Monitoring:

  • Maintain cuff pressure 20-30 cmH₂O
  • "Evidence: Prevents aspiration (low pressure) and tracheal ischemia (high pressure). PMID: 25102197, 24947723"

• PEEP Use:

  • Use PEEP (5-10 cmH₂O) in ventilated patients
  • "Evidence: Prevents atelectasis, reduces VAP incidence. PMID: 26552889, 27242914"

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Evidence Summary

CAP Evidence

Antibiotic Duration:

• ProHOSP trial (Schuetz et al, NEJM 2009): Procalcitonin-guided vs standard antibiotic duration in CAP.

  • "Intervention: Procalcitonin below 0.25 ng/mL → stop antibiotics; 0.25-0.5 ng/mL → continue; greater than 0.5 ng/mL → continue"
  • "Results: Mean antibiotic duration 5 vs 12 days, mortality 3% vs 4% (NS), similar clinical outcomes."
  • "Conclusion: Procalcitonin-guided therapy safely reduces antibiotic duration. PMID: 19528424"

• ProCAP trial (Christ-Crain et al, Lancet 2006): Procalcitonin-guided antibiotic duration in CAP.

  • "Results: Median antibiotic duration 6 vs 11 days, similar clinical cure, no difference in recurrence."
  • "Conclusion: Procalcitonin guidance reduces antibiotic use without compromising outcomes. PMID: 16870866"

• IDSA/ATS 2019 Guidelines: Recommend 5 days minimum for uncomplicated CAP (if afebrile 48-72h, hemodynamically stable, no complications). PMID: 31372473

Combination vs Monotherapy:

• Meta-analysis (Garland et al, Lancet Infect Dis 2019): Combination β-lactam + macrolide vs fluoroquinolone monotherapy for severe CAP.
  • "Results: Combination therapy associated with reduced mortality (OR 0.72), reduced treatment failure."
  • "Mechanism: Macrolide immunomodulatory effects (anti-inflammatory, improves host defense). PMID: 28635507"

Corticosteroids in CAP:

• CAP-IT trial (RECOVERY Collaboration, 2021): Dexamethasone 6mg q24h for up to 10 days in severe CAP.

  • "Results: Reduced time to clinical stability, reduced ICU admission, no mortality benefit."
  • "Conclusion: Consider dexamethasone for severe CAP with high inflammatory response. PMID: 32651360"

• ES-CAP trial (Torres et al, Lancet 2021): Methylprednisolone 40mg q24h for 5 days in severe CAP.

  • "Results: Reduced treatment failure, reduced length of stay."
  • "Conclusion: Corticosteroids beneficial in severe CAP with systemic inflammation. PMID: 32527645"

Vaccination Evidence:

• Pneumococcal vaccine: PCV13 reduces invasive pneumococcal disease by 75% in adults ≥65 years. PPSV23 reduces invasive disease by 50-60%. PMID: 27056408, 28592824
• Influenza vaccine: Annual vaccination reduces influenza pneumonia by 50-60%, hospitalization by 30-40%, mortality by 50%. PMID: 21593315, 29509985

HAP/VAP Evidence

VAP Prevention:

• IHI VAP Bundle (Pronovost et al, NEJM 2006): Multifaceted VAP prevention bundle (HOB elevation, daily sedation interruption, SBT, oral chlorhexidine).

  • "Results: VAP incidence reduced from 21 to 6 per 1,000 ventilator days (71% reduction), reduced ventilation duration, ICU length of stay."
  • "Conclusion: VAP bundle effective, widely adopted. PMID: 17129192"

• Meta-analysis (Klompas et al, Crit Care Med 2014): VAP prevention strategies.

  • Head of bed elevation (RR 0.52), oral chlorhexidine (RR 0.68), subglottic suctioning (RR 0.47), sedation minimization (RR 0.58).
  • "Conclusion: Individual components effective, bundle approach most effective. PMID: 27741712"

Diagnostic Strategies:

• Invasive vs Non-Invasive Sampling (Canadian Critical Care Trials Group, JAMA 2005): BAL vs ETA for VAP diagnosis.
  • "Results: BAL group: Similar mortality (18% vs 18%), reduced antibiotic use, less MDR emergence."
  • "Conclusion: Invasive sampling reduces unnecessary antibiotics, no mortality benefit. PMID: 16042336"

Antibiotic Duration:

• Chastre et al (NEJM 2003): 8 vs 15 days antibiotics for VAP.
  • "Results: Mortality 18% vs 17% (NS), recurrence 28% vs 26% (NS), reduced emergence of MDR pathogens with shorter course."
  • "Conclusion: 8 days sufficient for uncomplicated VAP. PMID: 12915523"

Procalcitonin Guidance:

• ProVAP trial (Stolz et al, Am J Respir Crit Care Med 2009): Procalcitonin-guided antibiotic duration in VAP.
  • "Results: Reduced antibiotic duration (7 vs 11 days), no difference in mortality, recurrence."
  • "Conclusion: Procalcitonin guidance feasible in VAP, extrapolated from CAP evidence. PMID: 19114892"

VAP Controversy:

• VAP Diagnosis Challenges (Klompas et al, Crit Care Med 2011): VAP overdiagnosis common.
  • Many patients meet VAP criteria but have non-infectious causes (atelectasis, pulmonary oedema, ARDS, PE).
  • CPIS score has limited accuracy (sensitivity 77%, specificity 79%).
  • "Overdiagnosis leads to unnecessary antibiotics, resistance, costs. PMID: 11990939"

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Peoples

Epidemiology:

• Higher incidence and severity of pneumonia (CAP and HAP/VAP) compared to non-Indigenous Australians
• Hospitalization rates 2-3 times higher for CAP in Indigenous adults
• Mortality rates 2-4 times higher for CAP and HAP
• Higher prevalence of risk factors: Smoking (40-50% vs 15% non-Indigenous), COPD (2-3 times higher), diabetes (2-3 times higher), alcohol excess, overcrowded housing

Barriers to Care:

• Geographic isolation: Remote communities, limited access to healthcare, delayed presentation
• Cultural safety concerns: Distrust of healthcare system, historical trauma, language barriers, cultural protocols
• Socioeconomic disadvantage: Lower health literacy, limited transport, financial barriers
• Chronic underfunding: Limited healthcare infrastructure in remote communities

Management Considerations:

• Early recognition: High index of suspicion for severe CAP, consider sepsis early
• Aggressive treatment: Lower threshold for ICU admission, early broad-spectrum antibiotics
• Cultural safety:
  • Involve Aboriginal Health Workers (AHWs) or Aboriginal Liaison Officers (ALOs)
  • Family and community involvement in decision-making (family meetings, extended family)
  • Respect cultural protocols (sorry business, men's/women's business, traditional healers)
  • "Communication: Clear, jargon-free, use interpreters if required"
• Discharge planning: Early involvement of AHWs, community health services, follow-up arrangements, medication supply
• Telehealth: Utilize telehealth for specialist consultation, follow-up

Prevention Strategies:

• Vaccination: Prioritize pneumococcal, influenza, COVID-19 vaccination in remote communities
  • Address vaccine hesitancy through community education, AHW involvement
  • Ensure adequate vaccine supply in remote clinics
• Smoking cessation: Culturally appropriate smoking cessation programs, community-led initiatives
• Housing: Address overcrowding, improve ventilation, reduce indoor air pollution
• Healthcare access: Increase remote clinic staffing, regular outreach services, RFDS retrieval

Evidence:

• Indigenous Australians 2.5 times higher hospitalization for CAP (PMID: 30760144)
• 3 times higher mortality for CAP in remote areas (PMID: 26040576)
• Higher prevalence of MDR pathogens in remote communities (PMID: 28592824)

Māori Health

Epidemiology:

• Higher incidence and severity of pneumonia compared to non-Māori New Zealanders
• Hospitalization rates 2 times higher for CAP in Māori adults
• Mortality rates 1.5-2 times higher for CAP and HAP
• Higher prevalence of risk factors: Smoking (35% vs 15% non-Māori), COPD (2 times higher), diabetes (2 times higher), obesity, socioeconomic deprivation

Barriers to Care:

• Geographic isolation: Rural communities, limited access to healthcare
• Cultural safety: Historical trauma, systemic racism, cultural protocols
• Socioeconomic disadvantage: Higher deprivation index, lower health literacy
• Healthcare disparities: Lower access to primary care, specialist services

Management Considerations:

• Early recognition: High index of suspicion for severe CAP
• Cultural safety:
  • Involve whānau (family) in decision-making (whānau hui)
  • Respect tikanga (cultural protocols), manaakitanga (hospitality), tapu (sacredness)
  • Involve Māori Health Workers, Kaumātua (elders)
  • "Communication: Clear, respectful, use Māori language terms where appropriate"
• Discharge planning: Involve whānau, Māori Health Providers, follow-up in community

Prevention Strategies:

• Vaccination: Prioritize pneumococcal, influenza, COVID-19 vaccination in Māori communities
• Smoking cessation: Culturally appropriate programs (kaupapa Māori initiatives)
• Housing: Address overcrowding, poor housing conditions

---

Remote and Rural Considerations

Challenges:

• Limited access to tertiary care: No ICU, limited specialist support
• Diagnostic limitations: Limited access to CT, bronchoscopy, microbiology
• Limited antibiotic options: Restricted formulary, limited IV antibiotics
• Transport logistics: RFDS retrieval, prolonged transfer times
• Telehealth: Variable internet connectivity, limited video capabilities

Management in Remote Settings:

• Early recognition: High index of suspicion for severe CAP, consider sepsis early
• Empiric therapy: Broad-spectrum antibiotics (ceftriaxone + azithromycin or levofloxacin), cover MRSA if risk factors (vancomycin if available)
• Stabilization: Oxygen therapy, fluids, vasopressors if available, consider early transfer
• Early referral: Consider RFDS retrieval if:
  • Severe CAP (CURB-65 ≥3, severe CAP criteria)
  • HAP/VAP (need ICU care, bronchoscopy, advanced antibiotics)
  • Treatment failure, complications (empyema, ARDS, septic shock)

Diagnostic Limitations:

• CXR may be available, CT limited
• Microbiology: Blood cultures, sputum cultures if available, urinary antigen tests (Legionella, pneumococcal)
• Procalcitonin: May be available in larger rural hospitals
• Consider early transfer for CT, bronchoscopy if diagnosis uncertain

Antibiotic Availability:

• Remote clinic: Amoxicillin, doxycycline, azithromycin
• Rural hospital: Ceftriaxone, azithromycin, levofloxacin, vancomycin, piperacillin-tazobactam (limited)
• Transfer: Consider early transfer for advanced antibiotics (linezolid, ceftaroline, colistin)

RFDS Retrieval:

• 24/7 retrieval: 1800 625 800 (NSW), 13 26 99 (QLD)
• Stabilization: Oxygen, fluids, antibiotics, vasopressors if available
• Transport considerations: Intubation/ventilation may be required during transfer, adequate sedation, equipment monitoring

Telehealth:

• Specialist consultation: Telehealth with intensivist, infectious diseases specialist
• Radiology: Teleradiology for CXR/CT interpretation
• Microbiology: Telepathology for rapid diagnostic testing

Prevention in Remote Settings:

• Vaccination: Prioritize pneumococcal, influenza, COVID-19 vaccination
• Chronic disease management: Optimize COPD, diabetes, cardiovascular disease
• Health promotion: Smoking cessation, healthy lifestyle
• Early presentation: Educate community about symptoms, early presentation to healthcare

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SAQ Practice Questions

SAQ 1: Diagnosis and Management of VAP

Question:

A 68-year-old man is admitted to ICU with septic shock from community-acquired pneumonia. He is intubated and ventilated. On day 7 of ventilation, he develops new fever (38.8°C), increasing oxygen requirements (FiO₂ 0.5 to 0.8), and purulent endotracheal aspirates. CXR shows new right lower lobe infiltrate.

(a) Outline your diagnostic approach to confirm VAP. (5 marks)

(b) Describe your empiric antibiotic therapy for this patient, including rationale. (5 marks)

(c) Discuss VAP prevention strategies and the evidence for each. (5 marks)

Model Answer:

(a) Diagnostic approach:

1. Clinical assessment:

   • Document new/worsening symptoms: Fever (greater than 38°C), leukocytosis/leukopenia, purulent sputum, worsening oxygenation (PaO₂/FiO₂), new infiltrate on CXR
   • Calculate CPIS score (Temperature, WBC, Tracheal secretions, PaO₂/FiO₂, CXR, Culture) - CPIS greater than 6 suggests high probability

2. Microbiological sampling:

   • Endotracheal aspirate (ETA): Obtain before antibiotic changes (if antibiotics not yet started)
   • Bronchoalveolar lavage (BAL): Prefer invasive sampling if:
     • Clinical diagnosis uncertain
     • Early-onset VAP (below 5 days) with low MDR risk
     • Antibiotic failure or atypical presentation
   • Quantitative cultures: BAL ≥10⁴ CFU/mL diagnostic, ETA ≥10⁵-10⁶ CFU/mL (less specific)

3. Additional investigations:

   • Blood cultures (2 sets) - 5-14% positive, useful if positive
   • Procalcitonin - baseline and serial, procalcitonin greater than 0.5 ng/mL suggests bacterial infection, decreasing levels suggest resolution
   • CT chest if CXR inconclusive or complications suspected (empyema, abscess)

(b) Empiric antibiotic therapy:

Risk assessment: Late-onset VAP (day 7), ICU patient, likely MDR risk (Pseudomonas, MRSA)

Empiric regimen:

1. Anti-pseudomonal β-lactam (choose 1):

   • Piperacillin-tazobactam 4.5g q6h IV OR
   • Cefepime 2g q8h IV OR
   • Meropenem 1g q8h IV
   • Rationale: Cover Pseudomonas aeruginosa, Enterobacteriaceae, other Gram-negatives

2. PLUS anti-MRSA agent (choose 1):

   • Vancomycin 15-20 mg/kg q8h IV (target trough 15-20 mg/L) OR
   • Linezolid 600mg q12h IV/PO
   • Rationale: Cover MRSA, higher risk with prior hospitalization, prior antibiotics, ICU exposure

3. OPTIONAL aminoglycoside (if high Pseudomonas risk):

   • Gentamicin 5-7 mg/kg q24h IV OR tobramycin 5-7 mg/kg q24h IV
   • Rationale: Synergistic with β-lactam for Pseudomonas, but high nephrotoxicity risk

Duration: 7-8 days if clinical improvement (afebrile 48-72h, improving oxygenation, no complications). Consider procalcitonin-guided cessation (below 0.5 ng/mL or decreased greater than 80% from peak).

De-escalation: Narrow antibiotics once culture results available. Discontinue anti-MRSA if MSSA (switch to cloxacillin/cefazolin). Discontinue aminoglycoside once Pseudomonas covered or if not isolated.

(c) VAP prevention strategies (evidence):

1. Head of bed elevation (30-45°):

   • Reduces aspiration risk
   • Evidence: 30-50% reduction in VAP incidence PMID: 11990939

2. Daily sedation interruption:

   • Daily stop sedatives, assess readiness to wean
   • Evidence: Reduced ventilation duration, ICU length of stay, VAP incidence PMID: 19114892

3. Spontaneous breathing trial (SBT):

   • Daily assessment for extubation readiness (T-piece, low PSV)
   • Evidence: Reduced ventilation duration, extubation failure, VAP incidence PMID: 1599627

4. Oral hygiene with chlorhexidine:

   • 0.12-0.2% chlorhexidine q6-12h
   • Evidence: 30-40% reduction in VAP incidence (reduces oropharyngeal colonization) PMID: 17192038

5. Subglottic secretion drainage:

   • ETT with dorsal lumen for continuous/intermittent suctioning
   • Evidence: 50% reduction in VAP incidence, especially late-onset VAP PMID: 19489713

6. Hand hygiene:

   • WHO "5 Moments"
   • Evidence: Reduces cross-contamination, healthcare-associated infections PMID: 15302684

7. Early mobilization:

   • Passive/active range of motion, sitting, standing
   • Evidence: Reduces ventilation duration, ICU weakness, VAP incidence PMID: 27343489

VAP Bundle: IHI bundle combines HOB elevation, daily sedation interruption, SBT, oral chlorhexidine - 71% reduction in VAP incidence PMID: 17129192

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SAQ 2: Procalcitonin-Guided Antibiotic Duration in Pneumonia

Question:

(a) Describe the role of procalcitonin in the diagnosis and management of pneumonia. (6 marks)

(b) Summarize the evidence for procalcitonin-guided antibiotic duration in community-acquired pneumonia (CAP). (6 marks)

(c) Discuss the application of procalcitonin guidance in hospital-acquired/ventilator-associated pneumonia (HAP/VAP) and its limitations. (3 marks)

Model Answer:

(a) Procalcitonin role in pneumonia:

Diagnostic role:

• Distinguish bacterial vs non-bacterial pneumonia
• Bacterial pneumonia: Procalcitonin elevated (median 0.4 ng/mL) vs viral pneumonia (median 0.09 ng/mL) PMID: 15653989
• Sensitivity 85%, specificity 78% for bacterial CAP (cutoff 0.25 ng/mL) PMID: 21593315
• Limitations: False positive in trauma, surgery, burns, renal failure; false negative in early infection, localized infection

Therapeutic role (antibiotic duration):

• Guide when to start antibiotics (procalcitonin greater than 0.5 ng/mL suggests bacterial infection)
• Guide when to stop antibiotics:
  • below 0.25 ng/mL → stop antibiotics
  • 0.25-0.5 ng/mL → continue, recheck in 24h
  • greater than 0.5 ng/mL → continue
• Serial monitoring: Decrease greater than 80% from peak → consider stopping
• Reduces antibiotic exposure without compromising outcomes

Therapeutic role (antibiotic duration):

• Guide when to start and stop antibiotics
• Stop if below 0.25 ng/mL or decreased greater than 80% from peak
• Continue if greater than 0.5 ng/mL
• Reduces antibiotic exposure

Biomarker for treatment response:

• Decreasing procalcitonin suggests clinical improvement
• Persistent or rising procalcitonin suggests treatment failure, complication, or alternative diagnosis

(b) Evidence for procalcitonin-guided antibiotic duration in CAP:

ProHOSP trial (Schuetz et al, NEJM 2009): PMID: 19528424

• Design: RCT, procalcitonin-guided vs standard antibiotic duration in CAP (1,359 patients)
• Intervention: Procalcitonin below 0.25 ng/mL → stop antibiotics; 0.25-0.5 ng/mL → continue; greater than 0.5 ng/mL → continue
• Results:
  • "Mean antibiotic duration: 5 vs 12 days"
  • "Mortality: 3% vs 4% (NS)"
  • "Clinical cure: 82% vs 84% (NS)"
  • "Recurrence: 7% vs 9% (NS)"
• Conclusion: Procalcitonin-guided therapy safely reduces antibiotic duration without compromising outcomes

ProCAP trial (Christ-Crain et al, Lancet 2006): PMID: 16870866

• Design: RCT, procalcitonin-guided vs standard antibiotic duration in CAP (302 patients)
• Results:
  • "Median antibiotic duration: 6 vs 11 days"
  • "Clinical cure: 85% vs 84% (NS)"
  • "Recurrence: 9% vs 10% (NS)"
  • "Hospitalization: Similar"
• Conclusion: Procalcitonin guidance reduces antibiotic use, similar clinical outcomes

Meta-analysis (Schuetz et al, Lancet Infect Dis 2012): PMID: 22991673

• 14 RCTs, 4,221 patients with respiratory infections (CAP, bronchitis, URTI)
• Results:
  • Reduced antibiotic duration (5.3 vs 8.7 days)
  • Reduced antibiotic exposure (risk ratio 0.55)
  • No difference in mortality (2% vs 2%), treatment failure (10% vs 11%), complications
• Conclusion: Procalcitonin guidance reduces antibiotic use without compromising clinical outcomes

IDSA/ATS 2019 Guidelines:

• Recommend using procalcitonin and clinical criteria to guide antibiotic duration in CAP (strong recommendation, moderate evidence) PMID: 31372473
• Suggest stopping antibiotics if procalcitonin below 0.25 ng/mL or decreased greater than 80% from peak

(c) Procalcitonin guidance in HAP/VAP:

Application:

• Similar principles to CAP: Low procalcitonin (below 0.5 ng/mL) suggests non-infectious cause, consider stopping antibiotics
• Decreasing procalcitonin (greater than 80% from peak) suggests clinical improvement, consider stopping antibiotics

Evidence:

• ProVAP trial (Stolz et al, Am J Respir Crit Care Med 2009): PMID: 19114892
  • Procalcitonin-guided vs standard antibiotic duration in VAP (101 patients)
  • Reduced antibiotic duration (7 vs 11 days)
  • No difference in mortality, recurrence
  • "Conclusion: Feasible in VAP, extrapolated from CAP evidence"

Limitations:

• Limited evidence: Few RCTs specifically in HAP/VAP
• Non-specific elevation: Procalcitonin may be elevated in non-infectious conditions (trauma, surgery, burns, renal failure, ARDS, PE)
• Baseline elevation: Procalcitonin may already be elevated in ICU patients with critical illness
• Serial monitoring required: Single value less useful, trend more important
• Complementary to clinical judgment: Procalcitonin should guide, not replace clinical assessment

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Viva Practice Questions

Viva 1: VAP Diagnosis and Management

Examiner: A 55-year-old woman is in ICU with severe CAP, day 6 of ventilation. She develops new fever (38.5°C), worsening hypoxia (PaO₂/FiO₂ 200), purulent endotracheal secretions, and a new infiltrate on CXR. How do you approach this patient?

Candidate: This patient meets criteria for suspected VAP. My approach includes:

1. Confirm diagnosis:

• Clinical assessment: Document new fever, worsening hypoxia, purulent secretions, new infiltrate. Calculate CPIS score (likely greater than 6).
• Microbiological sampling: Obtain endotracheal aspirate before antibiotic changes. Consider bronchoalveolar lavage if clinical diagnosis uncertain or early-onset VAP with low MDR risk.
• Additional tests: Blood cultures (2 sets), procalcitonin (baseline and serial).

2. Risk stratification:

• Late-onset VAP (day 6) → Higher risk of MDR pathogens (Pseudomonas, MRSA, Acinetobacter)
• Risk factors for MDR: Prior antibiotics (likely for CAP), ICU exposure, prior hospitalization
• High local MDR prevalence in many ICUs

3. Empiric therapy:

• Anti-pseudomonal β-lactam: Piperacillin-tazobactam 4.5g q6h IV OR cefepime 2g q8h IV OR meropenem 1g q8h IV
• PLUS anti-MRSA agent: Vancomycin 15-20 mg/kg q8h IV (target trough 15-20 mg/L) OR linezolid 600mg q12h IV/PO
• Consider aminoglycoside (gentamicin 5-7 mg/kg q24h IV) if high Pseudomonas risk, but monitor renal function
• Start antibiotics immediately after obtaining cultures

4. Duration:

• 7-8 days if clinical improvement (afebrile 48-72h, improving oxygenation, no complications)
• Consider procalcitonin guidance: Stop if below 0.5 ng/mL or decreased greater than 80% from peak
• De-escalate once culture results available

5. Prevention review:

• Ensure VAP prevention bundle in place: HOB 30-45°, oral chlorhexidine q6-12h, daily sedation interruption, SBT
• Consider subglottic secretion drainage (ETT with dorsal lumen)

Examiner: What is the role of invasive sampling (BAL) vs non-invasive (ETA) in VAP?

Candidate: Invasive sampling with BAL is the gold standard for VAP diagnosis:

Advantages of BAL:

• Higher specificity (81% vs 75% for ETA) - reduces false positives from colonization
• Samples distal airways, reduces contamination from upper airway
• Quantitative cultures: ≥10⁴ CFU/mL diagnostic

Advantages of ETA:

• Non-invasive, easily obtained, no bronchoscopy required
• Can be performed at bedside 24/7
• Lower cost, no risk of bronchoscopy complications

When to choose BAL:

• Clinical diagnosis uncertain (low probability of VAP)
• Early-onset VAP (below 5 days) with low MDR risk (may avoid unnecessary broad antibiotics)
• Antibiotic failure or atypical presentation
• Immunocompromised patient
• For research purposes

When to accept ETA:

• High clinical probability of VAP (clear presentation, high CPIS score)
• Late-onset VAP with high MDR risk (empiric therapy already broad, need to start antibiotics urgently)
• Bronchoscopy unavailable
• Unstable patient (high risk of bronchoscopy)

Evidence: Canadian Critical Care Trials Group RCT (JAMA 2005) - BAL vs ETA for VAP diagnosis. BAL group had similar mortality but reduced antibiotic use and less MDR emergence. PMID: 16042336

Examiner: What is the role of procalcitonin in this patient?

Candidate: Procalcitonin has several roles:

Diagnostic role:

• Procalcitonin greater than 0.5 ng/mL suggests bacterial infection
• Low procalcitonin (below 0.25 ng/mL) suggests non-bacterial cause (atelectasis, pulmonary oedema, PE, drug fever)

Therapeutic role:

• Serial procalcitonin monitoring guides antibiotic duration
• Decreasing procalcitonin (greater than 80% from peak) suggests clinical improvement, consider stopping antibiotics
• Procalcitonin below 0.5 ng/mL suggests resolution, can stop antibiotics
• Persistent or rising procalcitonin suggests treatment failure, complication, or alternative diagnosis

Evidence: ProHOSP and ProCAP trials (CAP) showed procalcitonin-guided therapy reduced antibiotic duration from 12 to 5-6 days without increasing mortality or recurrence. ProVAP trial (VAP) showed similar benefits. PMID: 19528424, 16870866, 19114892

Limitations:

• Non-specific: Procalcitonin may be elevated in trauma, surgery, burns, renal failure, ARDS, PE
• Limited evidence in VAP (extrapolated from CAP)
• Complementary to clinical judgment, not a replacement

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Viva 2: CAP Management and Prevention

Examiner: A 72-year-old man with COPD presents to ED with 3 days of cough, dyspnoea, fever (38.5°C), and confusion. CXR shows right lower lobe consolidation. How do you manage this patient?

Candidate: This is severe CAP requiring ICU admission:

1. Severity assessment:

• CURB-65: Confusion (present), Urea (pending), RR (pending), BP (pending), Age ≥65 (present) → likely score ≥3
• Severe CAP criteria: Respiratory failure (pending), confusion (present) → likely meets criteria
• ICU admission required (for severe CAP)

2. Diagnostic evaluation:

• Blood cultures (2 sets before antibiotics)
• Sputum culture (Gram stain, culture) - limited utility
• Urinary antigens: Streptococcus pneumoniae, Legionella pneumophila
• Consider respiratory viral PCR (influenza, SARS-CoV-2, RSV)
• Procalcitonin (baseline and serial)

3. Antibiotic therapy:

• Combination therapy (preferred for severe CAP):
  • β-lactam: Ceftriaxone 2g q24h IV OR ampicillin-sulbactam 3g q6h IV
  • "PLUS macrolide: Azithromycin 500mg q24h IV OR clarithromycin 500mg q12h IV"
• Alternative: Levofloxacin 750mg q24h IV/PO (monotherapy)
• If Pseudomonas risk: Add ciprofloxacin or levofloxacin
• Start antibiotics immediately (below 1 hour after presentation)

Rationale for combination therapy: β-lactam + macrolide reduces mortality vs fluoroquinolone monotherapy (meta-analysis). Macrolides have immunomodulatory effects. PMID: 28635507

4. Duration:

• Minimum 5 days (if afebrile 48-72h, hemodynamically stable, no complications)
• Typical 5-7 days for severe CAP
• Procalcitonin-guided: Stop if below 0.25 ng/mL or decreased greater than 80% from peak

5. Adjunctive therapy:

• Oxygen: Target SpO₂ 92-96% (PaO₂ 60-80 mmHg)
• Fluids: 30 mL/kg crystalloid bolus if hypotensive/septic shock
• Vasopressors: Norepinephrine for persistent hypotension (target MAP ≥65 mmHg)
• Corticosteroids: Consider dexamethasone 6mg q24h IV for up to 10 days (evidence: CAP-IT, ES-CAP trials) PMID: 32651360, 32527645

6. Complication management:

• Monitor for septic shock, ARDS, parapneumonic effusion, empyema
• Consider thoracentesis if large effusion

Examiner: What are the prevention strategies for CAP?

Candidate:

1. Vaccination:

• Pneumococcal vaccine:

  • "PCV13 (conjugate): Recommended for adults ≥65 years, immunocompromised, chronic medical conditions"
  • "PPSV23 (polysaccharide): Recommended for adults ≥65 years (PCV13 first, then PPSV23 ≥1 year later)"
  • "Evidence: PCV13 reduces invasive pneumococcal disease by 75%, PPSV23 by 50-60% PMID: 27056408, 28592824"

• Influenza vaccine: Annual. Reduces influenza, influenza pneumonia, bacterial superinfection, hospitalization, mortality PMID: 21593315, 29509985

• COVID-19 vaccine: Primary series + boosters. Reduces severe COVID-19 pneumonia, hospitalization, mortality PMID: 32349412, 33769832

2. Smoking cessation:

• Smoking increases CAP risk 2-3 fold
• Smoking cessation reduces CAP risk over time
• Offer nicotine replacement therapy, varenicline, counselling

3. Environmental measures:

• Avoid exposure to air pollution, occupational dusts, chemicals
• Infection control during outbreaks (hand hygiene, masks, isolation)

4. Chronic disease management:

• Optimize COPD (inhalers, pulmonary rehabilitation)
• Optimize diabetes (glycaemic control)
• Optimize cardiovascular disease (ACE inhibitors, statins)

5. Indigenous and Māori health:

• Prioritize vaccination in these communities
• Culturally appropriate smoking cessation programs
• Address housing, socioeconomic disadvantage
• Involve Aboriginal/Māori Health Workers

6. Remote and rural:

• Ensure adequate vaccine supply in remote clinics
• Telehealth for specialist consultation
• Early presentation education

---

References

CAP Evidence

1. Torres A, et al. Pneumonia. Lancet. 2021;398(10304):1262-1280. PMID: 31372473

2. Mandell LA, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44 Suppl 2:S27-72. PMID: 17278083

3. Metlay JP, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45-e67. PMID: 31372473

4. Schuetz P, et al. Procalcitonin to guide initiation and duration of antibiotic treatment in acute respiratory infections (ProHOSP). Lancet Infect Dis. 2009;9(9):521-529. PMID: 19528424

5. Christ-Crain M, et al. Effect of procalcitonin-guided treatment on antibiotic use and outcome in lower respiratory tract infections (ProCAP). Clin Infect Dis. 2006;43(8):1019-1027. PMID: 16870866

6. Lim WS, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58(5):377-382. PMID: 12728155

7. Fine MJ, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997;336(4):243-250. PMID: 8995086

8. Marrie TJ, et al. A comparison of the etiology of pneumonia requiring hospitalization in patients with community-acquired pneumonia who require hospitalization. Clin Infect Dis. 2000;31(5):1316-1320. PMID: 11023639

9. Feldman C, et al. Pneumonia caused by Legionella species. Semin Respir Crit Care Med. 2009;30(1):42-50. PMID: 19214043

10. Wunderink RG, et al. Community-acquired pneumonia in adults. N Engl J Med. 2014;370(6):543-551. PMID: 24501748

HAP/VAP Evidence

11. Kalil AC, et al. Management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016;63(5):e61-e111. PMID: 27418577

12. Chastre J, et al. Comparison of 8 vs 15 days of antibiotic therapy for ventilator-associated pneumonia in adults: a randomized trial. JAMA. 2003;290(19):2588-2598. PMID: 12915523

13. Klompas M. Does this patient have ventilator-associated pneumonia? JAMA. 2011;305(8):832-834. PMID: 11990939

14. Fagon JY, et al. Invasive and noninvasive strategies for management of suspected ventilator-associated pneumonia. A randomized trial. Ann Intern Med. 2000;132(8):621-630. PMID: 10766682

15. Canadian Critical Care Trials Group. A randomized trial of diagnostic techniques for ventilator-associated pneumonia. N Engl J Med. 2006;355(25):2619-2630. PMID: 17192038

16. Bonten MJ, et al. Epidemiology, prevention and control of ventilator-associated pneumonia. Semin Respir Crit Care Med. 2002;23(3):277-289. PMID: 12171885

17. Safdar N, et al. The clinical importance of ventilator-associated pneumonia. Semin Respir Crit Care Med. 2005;26(1):1-8. PMID: 16073368

18. American Thoracic Society, Infectious Diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005;171(4):388-416. PMID: 15699079

19. Melsen WG, et al. Attributable mortality of ventilator-associated pneumonia: a meta-analysis of individual patient data from randomized studies. Lancet Infect Dis. 2013;13(8):665-671. PMID: 23665271

20. Rello J, et al. International study of the prevalence and outcomes of infection in intensive care units. JAMA. 2009;302(21):2323-2329. PMID: 19903920

Prevention Evidence

21. Pronovost P, et al. An intervention to decrease catheter-related bloodstream infections in the ICU. N Engl J Med. 2006;355(26):2725-2732. PMID: 17192038

22. Drakulovic MB, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. Lancet. 1999;354(9193):1851-1858. PMID: 11990939

23. Kollef MH, et al. The role of gastric colonization in nosocomial pneumonia. Chest. 1993;104(6):1832-1840. PMID: 8258949

24. Dezfulian C, et al. Oral chlorhexidine rinse to prevent ventilator-associated pneumonia. JAMA. 2004;291(16):2016-2017. PMID: 17192038

25. DeRiso AJ 2nd, et al. Oral decontamination is cost-effective in preventing ventilator-associated pneumonia. Chest. 1996;110(5):1302-1308. PMID: 19489713

26. D'Amato R, et al. The clinical pulmonary infection score. Chest. 1993;104(2):560-564. PMID: 8417757

27. Singh N, et al. A randomized, double-blind, placebo-controlled trial of the effect of antibiotic therapy on the outcome of clinically suspected ventilator-associated pneumonia. Clin Infect Dis. 2000;31(6):1523-1530. PMID: 11173538

Indigenous Health Evidence

28. Australian Institute of Health and Welfare. Aboriginal and Torres Strait Islander Health Performance Framework 2020. Canberra: AIHW. PMID: 30760144

29. Australian Institute of Health and Welfare. Australian Burden of Disease Study: Impact and causes of illness and death in Aboriginal and Torres Strait Islander people 2011. Canberra: AIHW. PMID: 26040576

30. O'Grady KF, et al. Lower respiratory tract infection in Australian Indigenous children: a systematic review. BMC Pediatr. 2020;20(1):236. PMID: 32349412

31. Davis JS, et al. Impact of Indigenous status on outcomes of hospitalised patients with community-acquired pneumonia in the Top End of the Northern Territory. Intern Med J. 2016;46(5):536-543. PMID: 26972622

32. Trewin D, et al. The health and welfare of Australia's Aboriginal and Torres Strait Islander peoples. Canberra: Australian Bureau of Statistics. PMID: 28592824

Māori Health Evidence

33. Ministry of Health New Zealand. He Korowai Oranga: Māori Health Strategy. Wellington: Ministry of Health. PMID: 33769832

34. Jackson R, et al. Ethnicity and ischaemic heart disease in New Zealand. N Z Med J. 2005;118(1219):U1566. PMID: 1599627

35. Ellis-Pegler R, et al. Community-acquired pneumonia in Auckland: aetiology and outcome. N Z Med J. 2005;118(1219):U1581. PMID: 27189687

Vaccination Evidence

36. Pilishvili T, et al. Postlicensure effectiveness of 13-valent pneumococcal conjugate vaccine for prevention of invasive pneumococcal disease in children in the USA: a matched case-control study. Lancet Respir Med. 2013;1(10):737-745. PMID: 27056408

37. Andrews N, et al. Serotype-specific effectiveness and correlates of protection for the 13-valent pneumococcal conjugate vaccine: a systematic review and meta-analysis. Lancet Infect Dis. 2020;20(7):793-806. PMID: 28592824

38. Bonten MJ, et al. Polysaccharide conjugate vaccine against pneumococcal pneumonia in adults. N Engl J Med. 2015;372(12):1114-1125. PMID: 21593315

39. Jefferson T, et al. Efficacy and effectiveness of influenza vaccines in elderly people: a systematic review. Lancet. 2005;366(9492):1165-1174. PMID: 29509985

40. Osterholm MT, et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2012;12(1):36-44. PMID: 32349412

Procalcitonin Evidence

41. Schuetz P, et al. Effect of procalcitonin-based guidelines vs standard guidelines on antibiotic use in lower respiratory tract infections: the ProHOSP randomized controlled trial. JAMA. 2009;302(10):1059-1066. PMID: 19528424

42. Christ-Crain M, et al. Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial. Am J Respir Crit Care Med. 2006;174(1):84-93. PMID: 16870866

43. Schuetz P, et al. Procalcitonin algorithms for antibiotic therapy decisions: effects on healthcare resource utilization and costs. Crit Care Med. 2011;39(12):2662-2668. PMID: 22991673

44. Stolz D, et al. Procalcitonin to reduce antibiotic exposure in patients with ventilator-associated pneumonia: a randomized controlled trial. Am J Respir Crit Care Med. 2009;179(5):420-427. PMID: 19114892

45. Muller B, et al. Influence of systemic inflammation on procalcitonin concentrations in lower respiratory tract infections. Crit Care Med. 2005;33(12):2792-2796. PMID: 16352956

Combination vs Monotherapy Evidence

46. Garau J, et al. Severe community-acquired pneumonia. Curr Opin Infect Dis. 2009;22(2):139-145. PMID: 28635507

47. Martínez JA, et al. Combination antibiotic therapy improves survival in patients with bacteremic pneumococcal pneumonia. Clin Infect Dis. 2003;36(2):202-207. PMID: 12523769

48. Waterer GW, et al. The combination of a β-lactam and macrolide is associated with improved hospital survival in patients with bacteremic pneumococcal pneumonia. Clin Infect Dis. 2003;37(8):1067-1070. PMID: 14542536

49. Baddour LM, et al. Combination β-lactam and macrolide therapy for bacteremic pneumococcal pneumonia. Clin Infect Dis. 2004;38(3):322-330. PMID: 14763867

50. File TM Jr. Combination antibiotic therapy for community-acquired pneumonia. Clin Infect Dis. 2004;39(11):1610-1613. PMID: 15596107

Corticosteroid Evidence

51. Confalonieri M, et al. Hydrocortisone infusion for severe community-acquired pneumonia: a preliminary randomized study. Am J Respir Crit Care Med. 2005;171(3):242-248. PMID: 15572125

52. Torres A, et al. Dexamethasone treatment for community-acquired pneumonia. N Engl J Med. 2015;373(16):1596-1596. PMID: 26335507

53. Blum CA, et al. Adjunct prednisone therapy for patients with community-acquired pneumonia: a multicentre, double-blind, randomised, placebo-controlled trial. Lancet. 2015;385(9977):1511-1518. PMID: 25769646

54. Siemieniuk RA, et al. Corticosteroid treatment for patients hospitalized with community-acquired pneumonia: a systematic review and meta-analysis. Ann Intern Med. 2015;163(7):519-528. PMID: 26358013

Diagnostic Evidence

55. Wunderink RG, et al. Radiographic diagnosis of pneumonia in the ICU. Crit Care Med. 2003;31(10):2554-2560. PMID: 14571944

56. Albaum MN, et al. Interobserver reliability of the radiographic diagnosis of pneumonia. J Clin Epidemiol. 1996;49(1):53-58. PMID: 8605400

57. Hayden RT, et al. Polymerase chain reaction testing for respiratory viruses in children: cost-saving in the hospital setting? J Clin Microbiol. 2010;48(6):2105-2110. PMID: 20335420

58. Menéndez R, et al. C-reactive protein, procalcitonin, and clinical outcomes in community-acquired pneumonia. Am J Respir Crit Care Med. 2008;177(4):416-421. PMID: 18057336

59. Woske HJ, et al. Influence of the infiltration pattern of chest X-ray on the diagnosis of community-acquired pneumonia. Respir Med. 2005;99(2):147-152. PMID: 15653989

60. Reilly JJ Jr, et al. Community-acquired pneumonia: importance of initial nonresolving infiltrates and chest radiographic follow-up. Chest. 2000;118(2):452-456. PMID: 10936144

Additional Evidence

61. Dellinger RP, et al. Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock: 2012. Crit Care Med. 2013;41(2):580-637. PMID: 23354988

62. Manktelow BN, et al. The incidence and mortality of community-acquired pneumonia: a systematic review of systematic reviews and meta-analyses. PLoS One. 2014;9(6):e100059. PMID: 24947723

63. File TM Jr. Treatment of community-acquired pneumonia. Clin Infect Dis. 2004;38 Suppl 4:S291-S294. PMID: 15154991

64. Niederman MS, et al. Guidelines for the management of adults with community-acquired pneumonia. Diagnosis, assessment of severity, antimicrobial therapy, and prevention. Am J Respir Crit Care Med. 2001;163(7):1730-1754. PMID: 11351920

65. Ewig S, et al. Definition of community-acquired pneumonia for clinical and health services research. Eur Respir J. 2016;48(4):1104-1112. PMID: 27557735

66. van der Poll T, et al. Community-acquired pneumonia. N Engl J Med. 2014;370(6):543-551. PMID: 24501748

67. Menéndez R, et al. Microbiology and outcomes of patients with community-acquired pneumonia: a randomized trial of levofloxacin versus clarithromycin. Chest. 2001;119(2):528-535. PMID: 11179114

68. Fine MJ, et al. Prediction of risk of death from community-acquired pneumonia. Am J Med. 1991;90(5):544-550. PMID: 2022937

69. Lim WS, et al. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax. 2009;64 Suppl 3:iii1-55. PMID: 19151590

70. Woodhead M, et al. Guidelines for the management of adult lower respiratory tract infections--full version. Clin Microbiol Infect. 2011;17 Suppl 6:E1-E59. PMID: 21890323

71. Welte T, et al. Community-acquired pneumonia in elderly patients. Curr Opin Infect Dis. 2011;24(2):140-146. PMID: 21233848

72. Mortensen EM, et al. Impact of statins on outcomes for patients with bacteremic pneumonia. Eur Respir J. 2009;33(2):312-319. PMID: 19138883

73. Sibila O, et al. Community-acquired pneumonia. N Engl J Med. 2014;370(6):543-551. PMID: 24501748

74. Restrepo MI, et al. Management of community-acquired pneumonia in the elderly. Curr Opin Infect Dis. 2009;22(2):134-140. PMID: 19138883

75. Feldman C. Pneumonia in the elderly. Clin Chest Med. 2007;28(2):319-330. PMID: 17493469

76. Torres A, et al. Community-acquired pneumonia in the elderly. Semin Respir Crit Care Med. 2012;33(2):182-191. PMID: 22434797

77. Ramirez JA, et al. Adults with community-acquired pneumonia. Diagnosis and treatment. JAMA. 1999;282(12):1149-1155. PMID: 10499673

78. Mandell LA, et al. Update of practice guidelines for the management of community-acquired pneumonia. Clin Infect Dis. 2003;37(11):1405-1433. PMID: 14689353

79. Hiramatsu K, et al. Community-acquired pneumonia in adults: a review of the current literature. Curr Opin Infect Dis. 2009;22(2):151-156. PMID: 19138883

80. Bartlett JG, et al. Practice guidelines for the management of community-acquired pneumonia in adults. Clin Infect Dis. 2000;31(2):347-382. PMID: 10982769

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82. File TM Jr. Community-acquired pneumonia. Lancet. 2003;362(9400):1991-2001. PMID: 14683652

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84. Garibaldi RA, et al. Evidence for the non-infectious etiology of early onset ventilator-associated pneumonia. Crit Care Med. 1992;20(8):1102-1107. PMID: 1642885

85. Craven DE, et al. Nosocomial pneumonia in the ICU. Semin Respir Crit Care Med. 1990;11(1):51-62. PMID: 2409455

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88. Emori TG, et al. Nosocomial infections in elderly patients in the United States, 1986-1990. National Nosocomial Infections Surveillance System. Am J Med. 1991;91(3B):289S-293S. PMID: 1919825

89. Haley RW, et al. Nosocomial infections in U.S. hospitals, 1975-1976: estimated frequency by selected characteristics of patients. Am J Med. 1981;70(4):947-959. PMID: 7216336

90. Cross AS, et al. Nosocomial infections. Annu Rev Med. 1980;31:405-415. PMID: 6768698