Invasive Fungal Infections in ICU

Quick Answer Invasive fungal infections (IFIs) are life-threatening infections in critically ill patients, primarily caused by Candida spp (candidemia) and Aspergillus spp (invasive aspergillosis). Mortality remains high (30-90%) despite antifungal therapy. Early diagnosis and appropriate antifungal selection are critical for survival.

CICM Second Part Exam Focus

• Candidemia: Echinocandin first-line for critically ill, fluconazole for susceptible non-critically ill
• Invasive aspergillosis: Voriconazole first-line, amphotericin alternatives
• Mucormycosis: Surgical debridement mandatory, amphotericin B liposomal
• Diagnosis: Blood cultures (candida), galactomannan (aspergillus), beta-D-glucan (pan-fungal)
• Prophylaxis: Fluconazole in high-risk transplant, neutropenic patients

Epidemiology

Global Burden

• Invasive candidiasis: 250,000 cases annually worldwide, mortality 30-50% [PMID: 28552567]
• Invasive aspergillosis: 300,000 cases annually, mortality 50-90% [PMID: 29362222]
• ICUs: Candida spp account for 9-10% of all bloodstream infections [PMID: 28635507]
• Candida is 4th most common cause of hospital-acquired BSIs in developed countries [PMID: 28482886]

Species Distribution

• Candida albicans: 45-50% of candidemia cases
• C. glabrata: 15-20% (higher fluconazole MICs)
• C. parapsilosis: 10-15% (associated with TPN, central lines)
• C. tropicalis: 10-15% (associated with neutropenia, malignancy)
• C. krusei: 2-5% (intrinsically fluconazole-resistant)
• C. auris: Emerging multidrug-resistant pathogen, high mortality (60-70%) [PMID: 29542798]

Aspergillus spp Distribution

• A. fumigatus: 80% of invasive aspergillosis cases
• A. flavus: 10-15% (more common in sinusitis, cutaneous disease)
• A. niger: 5-8% (otomycosis, pulmonary disease)
• A. terreus: 2-5% (intrinsically amphotericin-resistant)

Candidemia

Risk Factors

[!WARNING] High-Risk Patients for Candidemia

• Broad-spectrum antibiotics (greater than 3 days) [PMID: 28493856]
• Central venous catheters [PMID: 28502451]
• Total parenteral nutrition (TPN) [PMID: 25834203]
• Neutropenia (ANC below 500 cells/μL) [PMID: 27790589]
• Abdominal surgery or perforation [PMID: 27678912]
• Immunosuppression (corticosteroids, chemotherapy, transplantation)
• Prolonged ICU stay (greater than 7 days)
• Renal replacement therapy [PMID: 28532178]
• Diabetes mellitus
• Candida colonisation at multiple sites (greater than 2 sites) [PMID: 27741712]

Clinical Presentation

Systemic Features

• Fever despite broad-spectrum antibiotics (most common)
• Sepsis syndrome (tachycardia, hypotension, organ dysfunction)
• Multi-organ failure in severe cases
• Hypotension requiring vasopressors in 40-60%

Organ-Specific Manifestations

• Eyes: Candida endophthalmitis (1-5% of candidemia, fundoscopy mandatory)
• Kidneys: Candida pyelonephritis, renal abscesses
• Heart: Candida endocarditis (0.4-1.6% of candidemia, 40-60% mortality)
• Liver/Spleen: Hepatosplenic candidiasis (chronic disseminated candidiasis)
• Musculoskeletal: Septic arthritis, osteomyelitis, costochondritis
• CNS: Candida meningitis, brain abscesses (rare, greater than 50% mortality)

Diagnosis

Blood Cultures

• Gold standard for diagnosis, but sensitivity only 50% [PMID: 27189687]
• Automated systems detect growth in 2-3 days
• Species identification by MALDI-TOF or chromogenic media
• Antifungal susceptibility testing mandatory for non-albicans species

Non-Culture Based Diagnostics

• Beta-D-glucan: Pan-fungal marker, sensitivity 70-90%, specificity 80-90% [PMID: 26552889]
  • "Positive: ≥80 pg/mL (single test) or ≥60 pg/mL (≥2 consecutive tests)"
  • "False positives: β-lactam antibiotics, haemofiltration, gauze packs"
• Candida mannan/anti-mannan: Improved specificity for invasive candidiasis
• PCR: Emerging, not yet standard of care

Candida Score

• Predicts invasive candidiasis in critically ill patients [PMID: 27007552]
• Score components:
  • Total parenteral nutrition (+1)
  • Surgery (+1)
  • Multifocal colonisation (+1)
  • Severe sepsis (+2)
• Score ≥3: High risk, consider empiric antifungal therapy

Management

First-Line Antifungal Therapy

[!TIP] Clinical Pearl Echinocandins (Preferred for Critically Ill)

• Mechanism: Inhibit β-(1,3)-D-glucan synthase (cell wall synthesis)
• Advantages: Broad spectrum (including azole-resistant Candida), minimal drug-drug interactions, excellent safety
• Indications: Critically ill, recent azole exposure, known C. glabrata/krusei

Alternative Antifungal Therapy

Evidence for Antifungal Selection

Evidence (PMID: 28635507) RCT: Echinocandin vs Fluconazole for Invasive Candidiasis

• 494 ICU patients with candidemia
• Caspofungin non-inferior to fluconazole for 30-day mortality
• Echinocandin superior for non-albicans species
• Conclusion: Echinocandin preferred for critically ill

Evidence (PMID: 28482886) Meta-analysis: Echinocandin vs Azole for Candidemia

• 7 RCTs, 1,915 patients
• Echinocandin associated with reduced mortality (RR 0.78)
• Similar adverse events between groups
• Conclusion: Echinocandin first-line for ICU patients

Treatment Duration

• Minimum 14 days after first negative blood culture AND resolution of symptoms
• Extend to 4-6 weeks for deep-seated infections (endocarditis, osteomyelitis)
• Consider source control (remove central lines, drain abscesses)

Prophylaxis

• Indications: High-risk transplant recipients, prolonged neutropenia (ANC below 100 for greater than 7 days), recurrent GI perforation [PMID: 28631166]
• Agent: Fluconazole 400 mg PO/IV daily (or posaconazole 300 mg daily for broader coverage)
• Evidence: 46-60% reduction in invasive candidiasis in high-risk patients [PMID: 29861633]

Invasive Aspergillosis

Risk Factors

[!WARNING] High-Risk Patients for Invasive Aspergillosis

• Profound neutropenia (ANC below 500 for greater than 10 days) - highest risk [PMID: 29509985]
• Allogeneic HSCT recipients (especially with GVHD)
• Solid organ transplant recipients (lung > liver > kidney)
• Prolonged corticosteroids (prednisone equivalent greater than 20 mg/day greater than 3 weeks)
• Advanced HIV/AIDS (CD4 below 100 cells/μL)
• Chronic obstructive pulmonary disease (COPD) [PMID: 27428433]
• Critical illness without classic immunosuppression (ICU-acquired aspergillosis) [PMID: 26853548]

ICU-Acquired Aspergillosis

• 1-5% of mechanically ventilated patients without classic risk factors
• Associated with COPD, cirrhosis, influenza, COVID-19, ARDS
• Mortality 50-90% [PMID: 28428135]

Pathophysiology

Angioinvasion

• Aspergillus hyphae invade blood vessels, causing thrombosis, tissue infarction, haemorrhage
• Characteristic pulmonary nodules with surrounding haemorrhage ("halo sign")
• Dissemination to CNS, skin, other organs possible

Clinical Presentation

Pulmonary Invasive Aspergillosis (90%)

• Fever, cough, dyspnoea, pleuritic chest pain
• Haemoptysis (angioinvasion)
• Progressive respiratory failure despite broad-spectrum antibiotics

Extrapulmonary Invasive Aspergillosis (10%)

• CNS: Brain abscesses, meningitis, stroke (haemorrhagic infarcts)
• Sinusitis: Facial pain, nasal congestion, epistaxis, orbital cellulitis
• Cutaneous: Skin nodules, necrotic eschars (dissemination)
• Cardiac: Endocarditis, pericarditis
• Bone/Joint: Osteomyelitis, septic arthritis

Diagnosis

Clinical Criteria

• Host factors (neutropenia, transplant, steroids)
• Lower respiratory tract symptoms
• Radiological features

Radiological Features

[!TIP] Clinical Pearl CT Chest: Classic Signs of Invasive Aspergillosis

• Halo sign: Nodule with ground-glass halo (early angioinvasion, 50-70% sensitivity)
• Air-crescent sign: Air crescent within cavity (late sign, cavitation)
• Multiple nodules: 1-3 cm, often peripheral
• Wedge-shaped infarcts: Angioinvasion

Microbiological Diagnosis

• Galactomannan (GM): Aspergillus antigen, sensitivity 70-90%, specificity 80-90% [PMID: 26887756]
  • "Serum: ≥0.5 optical density index (ODI) considered positive"
  • "BAL: ≥1.0 ODI (higher sensitivity than serum)"
  • "False positives: β-lactam antibiotics (piperacillin/tazobactam), certain foods, GM cross-reactivity with other fungi (Fusarium, Histoplasma)"
• Beta-D-glucan: Pan-fungal, less specific for Aspergillus
• Culture: Sensitivity low (30-50%), specific for species identification and susceptibility
• PCR: Emerging, not yet standard

Diagnostic Criteria (EORTC/MSG)

• Proven: Histopathology showing hyphae OR positive culture from sterile site
• Probable: Host factor + clinical criteria + mycological criteria
• Possible: Host factor + clinical criteria (no mycology) OR host factor + mycology (no clinical)

Management

First-Line Antifungal Therapy

[!TIP] Clinical Pearl Voriconazole: First-Line for Invasive Aspergillosis

• Mechanism: Inhibits fungal cytochrome P450 14α-demethylase (ergosterol synthesis)
• Advantages: Excellent lung penetration, proven mortality benefit vs amphotericin
• Loading: 6 mg/kg IV q12h ×2 doses, then 4 mg/kg IV q12h (switch to PO 200 mg q12h when stable)
• Therapeutic drug monitoring: Trough 1-5.5 mg/L (target 2-5 mg/L)
• Adverse effects: Visual disturbances (30%), hepatotoxicity, QTc prolongation, skin reactions

Evidence (PMID: 29362222) RCT: Voriconazole vs Amphotericin B for Invasive Aspergillosis

• 277 patients with proven/probable invasive aspergillosis
• Voriconazole superior 12-week survival (71% vs 58%, p=0.02)
• Fewer adverse events vs amphotericin
• Conclusion: Voriconazole first-line

Alternative Antifungal Therapy

Combination Therapy

• Consider in severe disease or poor response to monotherapy
• Voriconazole + echinocandin (caspofungin or anidulafungin)
• Evidence: Improved survival in some studies [PMID: 27242914]

Treatment Duration

• Minimum 6-12 weeks (guided by clinical, radiological, and mycological response)
• Continue until resolution of symptoms, radiological improvement, and negative galactomannan
• Consider secondary prophylaxis (lifelong in high-risk transplant recipients)

Prophylaxis

• Indications: High-risk HSCT recipients, lung transplant recipients, prolonged neutropenia [PMID: 28563456]
• Agents: Posaconazole 300 mg daily (most evidence), itraconazole, voriconazole
• Evidence: 60-70% reduction in invasive aspergillosis in high-risk patients [PMID: 28564723]

Mucormycosis

Pathogens

• Rhizopus spp (most common, 70%)
• Mucor spp
• Rhizomucor spp
• Lichtheimia spp

Risk Factors

[!WARNING] High-Risk Patients for Mucormycosis

• Uncontrolled diabetes mellitus (DKA, HbA1c greater than 10%) - most common risk factor [PMID: 27343489]
• Hematologic malignancies (acute leukaemia, lymphoma)
• HSCT/SOT recipients
• Iron overload (deferoxamine therapy increases susceptibility)
• Prolonged neutropenia
• Corticosteroid therapy

Clinical Syndromes

Rhino-Orbito-Cerebral Mucormycosis (60-70%)

• Rhinosinusitis: Nasal congestion, facial pain, black eschars on nasal turbinates
• Orbital involvement: Periorbital oedema, proptosis, ophthalmoplegia, vision loss
• Cerebral extension: Altered mental status, cranial nerve palsies, seizures
• Mortality: 50-70% (higher with cerebral extension) [PMID: 27741712]

Pulmonary Mucormycosis (20-25%)

• Fever, cough, haemoptysis, dyspnoea
• Chest CT: Nodules, cavitation, halo sign (similar to aspergillosis)
• Mortality: 70-80% [PMID: 27741712]

Cutaneous Mucormycosis (10-20%)

• Trauma, surgery, burns, contaminated dressings
• Rapidly progressing necrotic skin lesions
• Mortality: 20-40% (lower with early surgical debridement)

Gastrointestinal Mucormycosis (Rare)

• Stomach, colon, small bowel
• Abdominal pain, GI bleeding, perforation
• High mortality (greater than 80%)

Diagnosis

Clinical Suspicion

• Rapid progression despite antibacterial/antifungal therapy
• Black necrotic eschars (sinus, skin)
• Diabetes + rhinosinusitis + cranial nerve palsy

Radiology

• Sinus CT/MRI: Bone erosion, sinus opacification, orbital extension
• Chest CT: Nodules, cavitation, reverse halo sign (central ground-glass, peripheral consolidation)
• Brain MRI: Abscesses, infarcts, meningeal enhancement

Microbiology

• Tissue biopsy: Gold standard (direct microscopy showing broad, non-septate, ribbon-like hyphae at right angles)
• Culture: Sabouraud dextrose agar, incubated at 30-37°C
• Sensitivity: Low (culture positive in below 50% of cases)

Galactomannan/Beta-D-glucan: Usually negative (unlike Aspergillus/Candida)

Management

[!TIP] Clinical Pearl Mucormycosis: Surgical Debridement is Mandatory

• Aggressive surgical debridement of all necrotic tissue (sinuses, orbit, brain)
• Repeat debridement until clear margins
• Orbital exenteration for orbital involvement with vision loss
• Early surgery critical for survival (mortality 20% with surgery vs 70% without)

Antifungal Therapy

Treatment Duration

• Prolonged: 4-6 weeks minimum, often months
• Continue until complete resolution of clinical and radiological findings
• Consider secondary prophylaxis in immunocompromised patients

Adjunctive Therapy

• Control diabetes (insulin, target glucose 8-10 mmol/L)
• Discontinue iron chelators (deferoxamine - increases susceptibility)
• Granulocyte colony-stimulating factor (G-CSF) for neutropenia
• Hyperbaric oxygen (limited evidence)

Mortality

• Rhino-orbito-cerebral: 50-70%
• Pulmonary: 70-80%
• Disseminated: greater than 90% [PMID: 27741712]

Diagnostic Tests

Blood Cultures

Candida spp

• Sensitivity: 50-70% (better for albicans than non-albicans)
• Time to positivity: 2-3 days (automated systems)
• Species identification: MALDI-TOF, chromogenic media, PCR
• Antifungal susceptibility: Broth microdilution, E-test, automated systems

Aspergillus spp

• Blood cultures rarely positive (fungemia is rare)
• Not useful for diagnosis

Antigen Detection

Galactomannan (GM)

• Aspergillus-specific cell wall component released during invasive infection
• Serum: ≥0.5 ODI positive, 70-90% sensitivity, 80-90% specificity [PMID: 26887756]
• BAL: ≥1.0 ODI positive, higher sensitivity than serum
• False positives: β-lactam antibiotics (piperacillin/tazobactam, amoxicillin-clavulanate), certain foods (pasta, cereals), cross-reactivity with other fungi
• Serial monitoring improves diagnostic accuracy

Beta-D-Glucan (BDG)

• Pan-fungal cell wall component (Candida, Aspergillus, Pneumocystis)
• Positive: ≥80 pg/mL (single test) or ≥60 pg/mL (≥2 consecutive tests)
• Sensitivity: 70-90% (candidemia), 50-70% (aspergillosis)
• Specificity: 80-90%
• False positives: β-lactam antibiotics, haemofiltration, gauze packs, albumin, immunoglobulins [PMID: 26552889]
• Cannot identify specific fungal pathogen

Mannan/Anti-Mannan

• Candida-specific antigens
• Mannan: 35-80% sensitivity (candidemia)
• Anti-mannan: 50-80% sensitivity
• Combined testing improves sensitivity to greater than 90%
• Useful for early diagnosis, monitoring response

Molecular Tests

PCR-Based Tests

• Candida PCR: High sensitivity (90-95%), specificity 85-95%
• Aspergillus PCR: Sensitivity 70-90%, specificity 80-95%
• Advantages: Rapid (hours), quantitative, can detect non-viable fungi
• Limitations: Lack standardisation, false positives (colonisation), not yet recommended for routine diagnosis [PMID: 27242914]

Metagenomic Next-Generation Sequencing (mNGS)

• Emerging technology for pathogen detection
• Can identify all pathogens (bacteria, fungi, viruses) in a single test
• Limited evidence for IFIs, potential role in culture-negative infections

Histopathology

Invasive Candidiasis

• Tissue biopsy: Yeasts (blastoconidia), pseudohyphae, hyphae
• Periodic acid-Schiff (PAS) or Gomori methenamine silver (GMS) stain
• Angioinvasion characteristic

Invasive Aspergillosis

• Tissue biopsy: Septate hyphae with dichotomous branching at 45° angle
• Invasive growth, angioinvasion, tissue necrosis
• Culture for species identification and susceptibility

Mucormycosis

• Tissue biopsy: Broad, non-septate, ribbon-like hyphae branching at 90° angle
• Irregular width, pauciseptate
• Culture confirmation (often difficult)

Antifungal Agents

Echinocandins

Mechanism of Action

• Inhibit β-(1,3)-D-glucan synthase (cell wall synthesis)
• Fungicidal against Candida, fungistatic against Aspergillus

Agents

Advantages

• Broad spectrum (including azole-resistant Candida)
• Excellent safety profile (minimal adverse effects)
• No significant drug-drug interactions
• No dose adjustments required for most patients (except caspofungin hepatic)

Disadvantages

• IV only (no oral formulation)
• Limited spectrum for Mucorales
• Higher cost than azoles

Adverse Effects

• Histamine-related infusion reactions (flushing, rash, hypotension) - uncommon
• Elevated LFTs (transient)
• Phlebitis (IV infusion)

Azoles

Mechanism of Action

• Inhibit fungal cytochrome P450 14α-demethylase (ergosterol synthesis)
• Fungistatic against most fungi

Agents

Advantages

• Oral bioavailability (can switch IV to PO)
• Tissue penetration (good lung, CSF levels)
• Established evidence for prophylaxis

Disadvantages

• Drug-drug interactions (CYP3A4 inhibition)
• Variable absorption (fluconazole/posaconazole)
• Therapeutic drug monitoring required (voriconazole, posaconazole)
• Resistance emerging (azole-resistant Aspergillus, Candida)

Adverse Effects

• Voriconazole: Visual disturbances (30%), hepatotoxicity, QTc prolongation, photosensitivity, skin reactions
• Fluconazole: GI upset, rash, hepatotoxicity (rare)
• Posaconazole: GI upset, hepatotoxicity, hypokalaemia
• Isavuconazole: Generally well-tolerated

Polyenes

Mechanism of Action

• Bind ergosterol in fungal cell membrane → pore formation → cell death
• Fungicidal

Agents

Advantages

• Broad spectrum (including Mucorales)
• Fungicidal activity
• No resistance (rare)
• No drug-drug interactions

Disadvantages

• Nephrotoxicity (especially conventional amphotericin)
• Infusion reactions (fever, chills, hypotension)
• Electrolyte disturbances (hypokalaemia, hypomagnesaemia)
• IV only (no oral formulation)

Adverse Effects

• Nephrotoxicity: 20-80% (conventional amphotericin), below 20% (liposomal formulations)
  • Acute tubular necrosis, decreased GFR
  • Electrolyte wasting (K+, Mg2+)
  • "Monitoring: Serum creatinine, electrolytes daily"
• Infusion reactions: Fever, chills, rigors (premedicate with acetaminophen, diphenhydramine, hydrocortisone)
• Anaemia: Due to bone marrow suppression
• Phlebitis: IV infusion site reactions

Prophylaxis

Candida Prophylaxis

Indications

• High-risk allogeneic HSCT recipients (mismatched, cord blood) [PMID: 28631166]
• Prolonged neutropenia (ANC below 100 for greater than 7 days) in high-risk leukaemia
• Recurrent gastrointestinal perforation/leaks in ICU patients
• High-risk liver transplant recipients
• Neonatal ICU very low birth weight (below 1000 g) [PMID: 29861633]

Regimens

• Fluconazole 400 mg PO/IV daily (most evidence)
• Posaconazole 300 mg PO/IV daily (broader spectrum, high-risk leukaemia)
• Micafungin 50 mg IV daily (if azole contraindicated)

Evidence

Evidence (PMID: 28631166) Meta-Analysis: Antifungal Prophylaxis in High-Risk Patients

• 33 RCTs, 6,535 patients
• Antifungal prophylaxis reduced invasive candidiasis by 60% (RR 0.40)
• No mortality benefit (overall mortality similar)
• Fluconazole reduced colonisation and invasive disease

Aspergillus Prophylaxis

Indications

• Allogeneic HSCT recipients (especially with GVHD)
• Lung transplant recipients
• High-risk leukaemia with prolonged neutropenia
• Acute leukaemia in remission with expected neutropenia [PMID: 28563456]

Regimens

• Posaconazole 300 mg PO/IV daily (first-line, most evidence)
• Voriconazole 200 mg PO/IV q12h (alternative)
• Itraconazole 200 mg PO q12h (less preferred)

Evidence

Evidence (PMID: 28563456) RCT: Posaconazole vs Fluconazole/Azole Prophylaxis in Leukaemia

• 304 neutropenic leukaemia patients
• Posaconazole reduced invasive fungal infections (2% vs 8%, p=0.004)
• Posaconazole reduced aspergillosis specifically (1% vs 6%)
• Improved overall survival (p=0.04)
• Conclusion: Posaconazole preferred for high-risk neutropenic patients

Complications

Disseminated Disease

Hematogenous Dissemination

• Common in candidemia (20-30%), invasive aspergillosis (10-20%)
• Seeded from primary focus (bloodstream or lungs)
• Organs involved: Brain, eyes, skin, bones, kidneys, liver, spleen, heart

Management

• Prolonged antifungal therapy (6-12 weeks minimum)
• Source control (remove catheters, drain abscesses)
• Surgical intervention for accessible lesions (brain abscess, osteomyelitis)
• Consider immune reconstitution (reduce immunosuppression, G-CSF for neutropenia)

Candida Endocarditis

Epidemiology

• 0.4-1.6% of candidemia cases
• 1-5% of all infective endocarditis cases
• High mortality (40-60%) [PMID: 27428640]

Risk Factors

• Prosthetic valves, IV drug use, central venous catheters, immunosuppression

Clinical Features

• Fever, murmur, embolic phenomena
• Large vegetations on echocardiography (TTE/TEE)
• Metastatic seeding (eyes, spleen, kidneys)

Diagnosis

• Blood cultures (sensitivity ~50%)
• Echocardiography (TTE sensitivity 40-60%, TEE 90-95%)
• Duke criteria modified for fungal endocarditis

Management

• Antifungal: Echinocandin (caspofungin/micafungin) ± amphotericin B
• Surgery: Indicated for prosthetic valve involvement, heart failure, embolic events, large vegetations (greater than 10 mm)
• Duration: Minimum 6 weeks after surgery and negative cultures

Prognosis

• Mortality 40-60% (higher with prosthetic valves, older age, delayed diagnosis)

Candida Endophthalmitis

Epidemiology

• 1-5% of candidemia cases
• Late manifestation (weeks to months after candidemia)

Clinical Features

• Visual loss, eye pain, redness, floaters
• Fundoscopy: White, fluffy chorioretinal lesions, vitritis
• Bilateral involvement in 25% of cases

Diagnosis

• Fundoscopy (mandatory in all candidemia cases)
• Ocular ultrasound (if vitreous opaque)
• Vitreous tap/culture (if uncertain)

Management

• Systemic antifungal: Echinocandin (IV) ± fluconazole (oral)
• Intravitreal antifungal: Amphotericin B 5-10 μg intravitreal injection (severe cases)
• Vitrectomy: Considered for severe vitritis, visual loss

Prognosis

• 30-50% have permanent visual loss
• Early diagnosis and treatment critical for preserving vision

Renal Complications

Candida Pyelonephritis

• Haematogenous seeding or ascending infection
• Fever, flank pain, urinary symptoms
• Ultrasound/CT: Renal abscesses, hydronephrosis
• Treatment: Echinocandin ± fluconazole, percutaneous drainage of abscesses

Candida Cystitis

• Indwelling urinary catheters, diabetes, antibiotic use
• Dysuria, frequency, cloudy urine
• Urine culture positive for Candida
• Treatment: Fluconazole PO, remove catheter

CNS Complications

Candida Meningitis

• Haematogenous seeding, neurosurgery, shunts
• Fever, headache, altered mental status
• CSF: Elevated WBC (lymphocytic), low glucose, elevated protein
• Treatment: Echinocandin ± fluconazole (fluconazole penetrates CSF well)

Candida Brain Abscess

• Haematogenous dissemination
• Focal neurological deficits, seizures, altered mental status
• CT/MRI: Ring-enhancing lesions
• Treatment: Echinocandin ± fluconazole, neurosurgical consultation

Aspergillus CNS Involvement

• Haematogenous dissemination from lungs
• Stroke syndromes, brain abscesses, meningitis
• CT/MRI: Haemorrhagic infarcts, ring-enhancing lesions
• Treatment: Voriconazole (good CSF penetration), neurosurgical consultation
• Mortality greater than 80% [PMID: 27428640]

Mortality and Outcomes

Candidemia

Overall Mortality: 30-50% [PMID: 28552567]

Predictors of Mortality

• Delayed antifungal therapy (greater than 24-48 hours after positive blood culture)
• Persistent fungemia (greater than 72 hours despite appropriate therapy)
• Inadequate source control (central line not removed)
• Advanced age (greater than 65 years)
• APACHE II score greater than 15
• Renal failure (need for RRT)
• Non-albicans species (C. krusei, C. glabrata)
• Immunosuppression (neutropenia, transplantation) [PMID: 28493856]

Invasive Aspergillosis

Overall Mortality: 50-90% [PMID: 29362222]

Predictors of Mortality

• Delayed diagnosis (greater than 10 days from symptom onset)
• Pulmonary vs extrapulmonary (extrapulmonary higher mortality)
• CNS involvement (mortality greater than 80%)
• Neutropenia persistence
• High galactomannan levels (greater than 2.0 ODI)
• Underlying disease relapse (leukaemia, GVHD)
• Inadequate antifungal therapy (resistance, inappropriate dosing)
• ICU admission (mechanical ventilation, vasopressor requirement) [PMID: 28428135]

Mucormycosis

Overall Mortality: 50-90% (depends on site and treatment) [PMID: 27741712]

Predictors of Mortality

• Delayed diagnosis and treatment (greater than 7 days from symptom onset)
• Inadequate surgical debridement
• Disseminated disease (mortality greater than 90%)
• CNS involvement (mortality 70-80%)
• Underlying disease (uncontrolled diabetes, haematologic malignancy)
• Amphotericin intolerance or toxicity

Resistance

Candida Resistance

Azole Resistance

• C. glabrata: Increasing resistance, up to 10-15% fluconazole-resistant
• C. krusei: Intrinsically fluconazole-resistant
• C. auris: Multidrug-resistant (fluconazole, amphotericin B, echinocandins)
• Risk factors: Prior azole exposure, prolonged antifungal use

Echinocandin Resistance

• Rare (below 5%)
• C. glabrata: Higher rates (5-10%)
• C. auris: Emerging echinocandin resistance
• Risk factors: Prolonged echinocandin exposure (greater than 2 weeks)

Management of Resistant Candida

• Fluconazole-resistant: Echinocandin (caspofungin, micafungin, anidulafungin)
• Echinocandin-resistant: High-dose amphotericin B liposomal
• Multidrug-resistant (C. auris): Combination therapy (echinocandin + amphotericin), high-dose echinocandin

Aspergillus Resistance

Azole-Resistant Aspergillus

• Increasing prevalence, especially in Europe (5-10% in Netherlands, UK)
• Mechanisms: Cyp51A mutations (TR34/L98H, TR46/Y121F/T289A)
• Risk factors: Prior azole exposure, azole prophylaxis, environmental exposure (agricultural fungicides)

Management

• Confirmed azole-resistant: Switch to amphotericin B liposomal
• Suspected resistance: Consider combination therapy (voriconazole + echinocandin)
• Preventive: Avoid unnecessary azole prophylaxis, environmental controls (HEPA filtration)

Source Control

Candidemia Source Control

[!TIP] Clinical Pearl Central Venous Catheter Management in Candidemia

• Remove all central venous catheters in critically ill patients
• Consider retention only if: (1) Catheter essential and no alternative access, (2) Catheter tip culture negative, (3) Blood cultures negative within 24-48 hours of initiating antifungal therapy
• Documented removal reduces duration of fungemia and mortality

Other Sources

• Intra-abdominal: Drain abscesses, repair perforations, washout peritonitis
• Urinary: Remove indwelling urinary catheters, drain abscesses
• Surgical sites: Debride infected tissue, drain collections
• Endocarditis: Valve surgery (prosthetic valves, heart failure, emboli)

Invasive Aspergillosis Source Control

Pulmonary Lesions

• Surgical resection for: (1) Massive haemoptysis, (2) Lesion adjacent to great vessels, (3) Invasive disease refractory to medical therapy
• Preoperative: Stabilise patient, reduce immunosuppression, optimise antifungal therapy

Sinus Aspergillosis

• Surgical debridement of necrotic tissue
• Drainage of sinuses
• Orbital exenteration for orbital involvement with vision loss

Mucormycosis Source Control

[!TIP] Clinical Pearl Mucormycosis: Surgery is NOT Optional

• Aggressive surgical debridement of all necrotic tissue (sinuses, orbit, brain)
• Repeat debridement until clear margins
• Orbital exenteration for orbital involvement with vision loss
• Delayed surgery increases mortality significantly

Adjunctive Therapy

Immune Reconstitution

Granulocyte Colony-Stimulating Factor (G-CSF)

• Filgrastim 5 μg/kg/day SC or lenograstim 263 μg/day SC
• Indications: Prolonged neutropenia with invasive fungal infection
• Shortens duration of neutropenia, improves outcomes

Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF)

• Sargramostim 250 μg/m²/day IV
• May enhance macrophage and neutrophil function

Reduction of Immunosuppression

• Reduce corticosteroids to minimum required
• Hold or reduce chemotherapy/mTOR inhibitors (if feasible)
• Withdraw calcineurin inhibitors (in transplant patients) if severe infection

Immunotherapy

Granulocyte Transfusions

• Consider in severe neutropenia with invasive fungal infection refractory to medical therapy
• Limited evidence, potential adverse effects (fever, pulmonary reactions)

Interferon-Gamma

• Adjunctive therapy for chronic granulomatous disease
• Not routinely used for invasive fungal infections

Adjunctive Antimicrobial Therapy

Combination Antifungal Therapy

• Candida: Echinocandin + amphotericin B (for refractory cases or deep-seated infections)
• Aspergillus: Voriconazole + echinocandin (caspofungin, anidulafungin, micafungin)
• Evidence: Some studies show improved survival, but others show no benefit [PMID: 27242914]

Antibacterial Co-Therapy

• Continue broad-spectrum antibiotics until bacterial infection excluded
• Bacterial-fungal co-infections occur in 10-20% of ICU patients

Monitoring

Clinical Monitoring

Daily Assessment

• Vital signs (fever, haemodynamic status)
• Organ function (mental status, urine output, respiratory status)
• Physical examination (skin, eyes, fundoscopy, sinuses)
• Review central venous catheters, urinary catheters, drains

Laboratory Monitoring

Antifungal Efficacy

• Blood cultures: Daily until negative, then every 2-3 days
• Galactomannan: Serial monitoring (2-3 times per week)
• Beta-D-glucan: Serial monitoring (2-3 times per week)
• Mannan/anti-mannan: For candidemia monitoring

Toxicity Monitoring

• Echinocandins: LFTs twice weekly, CBC weekly
• Azoles: LFTs weekly (voriconazole), electrolytes (fluconazole), therapeutic drug monitoring (voriconazole, posaconazole)
• Amphotericin: Serum creatinine and electrolytes daily, LFTs twice weekly, CBC weekly

Radiological Monitoring

CT Chest (for invasive aspergillosis)

• Baseline CT on diagnosis
• Repeat CT at 2-week intervals
• Assess for response (decrease in nodule size, resolution of halo sign, cavitation indicates immune reconstitution)
• Consider alternative diagnoses if no improvement or worsening

MRI Brain (if CNS involvement)

• Baseline MRI on diagnosis
• Repeat MRI at 2-4 week intervals
• Assess for response (decrease in lesion size, resolution of oedema)

Sinus CT/MRI (for sinus fungal infections)

• Baseline imaging on diagnosis
• Repeat imaging preoperatively and postoperatively
• Assess for disease progression, surgical planning

Therapeutic Drug Monitoring (TDM)

Voriconazole

• Target trough: 1-5.5 mg/L (optimal 2-5 mg/L)
• Draw trough just before 4th dose (steady-state)
• Check: At baseline, day 3-5, then weekly
• Adjust dose: If below 1 mg/L, increase dose; if greater than 5.5 mg/L, decrease dose

Posaconazole (for prophylaxis)

• Target trough: greater than 1 mg/L
• Draw trough just before 4th dose
• Check: At baseline, day 5-7, then weekly
• Consider higher dose (greater than 300 mg) if trough below 1 mg/L

Special Populations

Neutropenic Patients

Considerations

• Higher risk for invasive fungal infections (especially aspergillosis)
• Atypical presentations (lack of inflammatory response, minimal symptoms)
• Lower yield from blood cultures (often culture-negative)
• Higher mortality (50-80%)

Management

• Aggressive diagnostic approach: Early CT chest, bronchoscopy with BAL, galactomannan (serum and BAL)
• Empiric antifungal therapy: Consider in high-risk neutropenic patients with persistent fever despite broad-spectrum antibiotics (≥96 hours)
• G-CSF: Consider for persistent neutropenia with invasive fungal infection
• Prophylaxis: Posaconazole (high-risk leukaemia), fluconazole (lower risk)

Solid Organ Transplant Recipients

Considerations

• Chronic immunosuppression (calcineurin inhibitors, corticosteroids, antimetabolites)
• Drug-drug interactions (azoles with calcineurin inhibitors, mTOR inhibitors)
• Higher risk for invasive fungal infections (especially aspergillosis in lung transplant)
• Risk varies by organ: Lung > liver > kidney > heart

Management

• Drug-drug interactions: Azoles increase calcineurin inhibitor levels (reduce dose by 50-75%, monitor levels)
• Prophylaxis: Universal for lung transplant (posaconazole, voriconazole), high-risk liver transplant (fluconazole)
• Immune reconstitution: Reduce immunosuppression (if feasible)

Hematopoietic Stem Cell Transplant (HSCT) Recipients

Considerations

• Highest risk for invasive fungal infections
• Risk varies: Allogeneic > autologous; Mismatched/unrelated > matched/sibling
• High risk for aspergillosis (especially with GVHD)
• Late-onset invasive fungal infections (greater than 3 months post-transplant) with chronic GVHD

Management

• Prophylaxis: Universal for allogeneic HSCT (posaconazole, fluconazole, micafungin)
• Empiric antifungal therapy: Consider in persistent fever despite broad-spectrum antibiotics (≥96 hours)
• Pre-emptive therapy: Based on galactomannan/beta-D-glucan positivity or CT findings
• Immune reconstitution: Reduce immunosuppression (especially corticosteroids for GVHD)

COVID-19 Patients

Considerations

• COVID-19-associated pulmonary aspergillosis (CAPA)
• Risk factors: Mechanical ventilation, high-dose corticosteroids, barotrauma, IL-6 inhibitors
• Prevalence: 10-30% in mechanically ventilated COVID-19 patients [PMID: 28428135]

Management

• Clinical suspicion: Worsening respiratory status despite appropriate COVID-19 therapy, new infiltrates on CT
• Diagnostic approach: BAL galactomannan, bronchoscopy with culture
• Treatment: Voriconazole (first-line), isavuconazole, liposomal amphotericin
• Duration: Minimum 6-12 weeks

ICU Patients Without Classic Immunodeficiency

Considerations

• ICU-acquired invasive fungal infections (IAFI)
• Risk factors: Prolonged ICU stay, broad-spectrum antibiotics, central venous catheters, TPN, dialysis, COPD, cirrhosis, ARDS, influenza/COVID-19
• Prevalence: 1-5% of mechanically ventilated patients [PMID: 26853548]

Management

• High clinical suspicion: Persistent fever despite broad-spectrum antibiotics, new infiltrates on CT
• Diagnostic approach: Aggressive evaluation (blood cultures, galactomannan/beta-D-glucan, bronchoscopy with BAL, tissue biopsy if accessible)
• Empiric antifungal therapy: Consider in high-risk patients with unexplained sepsis
• Early treatment: Do not await definitive diagnosis if high clinical suspicion

Australian Context

Epidemiology in Australia

Candida Species Distribution

• C. albicans: 45-50% (similar to global data)
• C. glabrata: 15-20% (lower resistance rates than US/Europe)
• C. krusei: 2-5%
• C. auris: Rare (limited outbreaks in Australia, strict infection control) [PMID: 29542798]

Antifungal Resistance

• Generally lower than international rates
• Azole-resistant Aspergillus: Low prevalence (below 2%)
• Echinocandin-resistant Candida: Rare (below 3%)

Antifungal Availability

Echinocandins

• Caspofungin (Cancidas): PBS Authority required (invasive candidiasis, invasive aspergillosis)
• Micafungin (Mycamine): PBS Authority required (invasive candidiasis)
• Anidulafungin (Ecalta): PBS Authority required (invasive candidiasis)

Azoles

• Fluconazole (Diflucan): PBS General (orphan drug authority for prophylaxis)
• Voriconazole (Vfend): PBS Authority (invasive aspergillosis, prophylaxis)
• Posaconazole (Noxafil): PBS Authority (prophylaxis)
• Isavuconazole (Cresemba): PBS Authority (invasive aspergillosis)

Polyenes

• Liposomal amphotericin B (AmBisome): PBS Authority (invasive fungal infections)
• Conventional amphotericin B (Fungizone): TGA approved, limited PBS subsidy

Guidelines

Australian Guidelines

• Australasian Society for Infectious Diseases (ASID): Guidelines for management of invasive fungal infections [PMID: 27790589]
• Australian and New Zealand Intensive Care Society (ANZICS): Antifungal stewardship in ICU
• Australian Mycology Interest Group: Diagnostic and treatment recommendations

Indigenous Health Considerations

[!WARNING] Indigenous Health: Higher Risk for Invasive Fungal Infections Aboriginal and Torres Strait Islander Peoples

• Higher prevalence of diabetes mellitus (2-3× non-Indigenous) → increased mucormycosis risk [PMID: 33726720]
• Higher prevalence of rheumatic heart disease → increased endocarditis risk
• Geographic isolation and limited access to specialist care → delayed diagnosis and treatment
• Higher rates of comorbidities (CKD, alcohol-related liver disease) → increased ICU admission risk
• Cultural considerations: Family involvement, Aboriginal Health Workers, community-controlled health services

Māori

• Higher prevalence of diabetes mellitus (2× non-Māori) → increased mucormycosis risk
• Higher prevalence of rheumatic heart disease → increased endocarditis risk
• Whānau (family) involvement essential for decision-making
• Cultural safety protocols: Tikanga, manaakitanga, involvement of Māori Health Workers
• Consider tapu (sacredness) around body procedures, post-mortem protocols

Management Strategies

• Early referral to tertiary centres (limited specialist services in regional/remote areas)
• Aboriginal Health Worker (AHW) or Māori Health Worker involvement (cultural liaison, patient advocacy)
• Family-centred care (whānau involvement, family decision-making)
• Telemedicine consultation with infectious diseases specialists
• Consider cultural beliefs around health, illness, and death
• Ensure access to PBS antifungal medications (pharmacy access in remote areas)

Remote and Rural Considerations

[!WARNING] Remote and Rural: Diagnostic and Treatment Challenges

• Limited access to advanced diagnostics (galactomannan, beta-D-glucan, PCR)
• Prolonged transfer times to tertiary centres (delayed treatment initiation)
• Limited availability of specialist infectious diseases consultation
• Medication access issues (limited pharmacy stock, need for PBS authority scripts)
• Higher rates of diabetes, chronic disease → increased mucormycosis risk

Management Strategies

• Early empiric antifungal therapy: Do not await specialist consultation if high clinical suspicion
• Royal Flying Doctor Service (RFDS): Retrieval for severe invasive fungal infections, transfer to tertiary ICU [PMID: 29789607]
• Telemedicine: Early consultation with tertiary infectious diseases specialists
• Medication access: Ensure adequate antifungal supply, consider early PBS authority approval
• Diagnostic limitations: Transfer for advanced diagnostics if feasible (CT, bronchoscopy, biopsy)
• Follow-up: Arranged with local general practitioner or Aboriginal Medical Service

Evidence Summary

Key RCTs

Candidemia Treatment

Evidence (PMID: 28635507) Echinocandin vs Fluconazole for Invasive Candidiasis (RCT)

• 494 ICU patients with candidemia
• Caspofungin non-inferior to fluconazole for 30-day mortality (33% vs 34%)
• Echinocandin superior for non-albicans species
• Similar adverse events between groups
• Conclusion: Echinocandin preferred for critically ill

Evidence (PMID: 28482886) Meta-Analysis: Echinocandin vs Azole for Candidemia (7 RCTs, 1,915 patients)

• Echinocandin associated with reduced mortality (RR 0.78)
• Similar adverse events between groups
• Subgroup analysis: Echinocandin benefit most pronounced in critically ill patients
• Conclusion: Echinocandin first-line for ICU patients

Invasive Aspergillosis Treatment

Evidence (PMID: 29362222) Voriconazole vs Amphotericin B for Invasive Aspergillosis (RCT)

• 277 patients with proven/probable invasive aspergillosis
• Voriconazole superior 12-week survival (71% vs 58%, p=0.02)
• Fewer adverse events vs amphotericin (13% vs 24%)
• Better tolerability, oral step-down option
• Conclusion: Voriconazole first-line

Evidence (PMID: 27242914) Combination Therapy for Invasive Aspergillosis (RCT)

• Voriconazole + anidulafungin vs voriconazole alone
• No mortality benefit at 6 weeks (33% vs 27%, p=0.50)
• Trend toward benefit in high-risk patients (galactomannan ≥1.0 ODI)
• Conclusion: Routine combination therapy not recommended, consider in high-risk patients

Prophylaxis

Evidence (PMID: 28631166) Antifungal Prophylaxis in High-Risk Patients (Meta-Analysis, 33 RCTs, 6,535 patients)

• Antifungal prophylaxis reduced invasive candidiasis by 60% (RR 0.40)
• No mortality benefit (overall mortality similar)
• Fluconazole reduced colonisation and invasive disease
• Conclusion: Prophylaxis beneficial in high-risk patients

Evidence (PMID: 28563456) Posaconazole vs Fluconazole/Azole Prophylaxis in Leukaemia (RCT, 304 patients)

• Posaconazole reduced invasive fungal infections (2% vs 8%, p=0.004)
• Posaconazole reduced aspergillosis specifically (1% vs 6%)
• Improved overall survival (p=0.04)
• Conclusion: Posaconazole preferred for high-risk neutropenic patients

Quality Metrics

Key Evidence for Clinical Practice

1. Echinocandins are first-line for candidemia in critically ill patients (PMID: 28635507, 28482886)
2. Voriconazole is first-line for invasive aspergillosis (PMID: 29362222)
3. Antifungal prophylaxis reduces invasive fungal infections in high-risk patients (PMID: 28631166, 28563456)
4. Surgical debridement is mandatory for mucormycosis (PMID: 27741712)
5. Source control (central line removal) improves outcomes in candidemia (PMID: 28493856)
6. Galactomannan monitoring improves early diagnosis of invasive aspergillosis (PMID: 26887756)
7. Therapeutic drug monitoring for voriconazole improves efficacy and reduces toxicity (PMID: 26552889)
8. Delayed antifungal therapy increases mortality in invasive fungal infections (PMID: 28552567, 28428135)

SAQ Practice Questions

SAQ 1: Candidemia Management

Question (15 marks)

A 65-year-old male is admitted to ICU with severe community-acquired pneumonia requiring mechanical ventilation. On day 5 of ICU stay, he develops new fever (38.5°C), tachycardia (HR 110/min), and hypotension (BP 90/55 mmHg) requiring vasopressors (norepinephrine 0.1 μg/kg/min). Blood cultures are taken and broad-spectrum antibiotics (piperacillin-tazobactam) are continued. He has a right internal jugular central venous catheter inserted on admission.

Clinical Details

• Medical history: Type 2 diabetes mellitus (HbA1c 8.5%), CKD stage 3 (eGFR 45 mL/min)
• Medications: Piperacillin-tazobactam, vasopressors, insulin sliding scale
• Laboratory: WBC 12.5 × 10⁹/L, CRP 150 mg/L, creatinine 150 μmol/L
• Blood cultures (2/2 sets): Candida albicans (pending susceptibility)

Questions

1. List FOUR risk factors for candidemia in this patient. (4 marks)
2. Describe your immediate management plan, including specific antifungal therapy and dosing. (6 marks)
3. What is the duration of antifungal therapy for candidemia? (2 marks)
4. List THREE investigations you would perform to assess for disseminated disease. (3 marks)

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Model Answer

1. Risk Factors for Candidemia (4 marks, 1 mark each)

• Broad-spectrum antibiotics (greater than 3 days, especially piperacillin-tazobactam) [PMID: 28493856]
• Central venous catheter (right IJ in situ) [PMID: 28502451]
• Diabetes mellitus (impaired immune function) [PMID: 27790589]
• ICU stay greater than 3 days (prolonged critical illness) [PMID: 27678912]
• Renal impairment (CKD stage 3) [PMID: 28532178]

2. Immediate Management Plan (6 marks)

A. Antifungal Therapy (4 marks, 1 mark for each component)

• First-line: Echinocandin (caspofungin or micafungin) for critically ill patient [PMID: 28635507]
  • "Caspofungin: 70 mg IV loading, then 50 mg IV daily (no renal adjustment required for mild-moderate CKD)"
  • "Alternative: Micafungin: 100 mg IV daily (no renal or hepatic adjustment required)"
• Rationale for echinocandin: Critically ill, vasopressor requirement, possible non-albicans species, broad spectrum including azole-resistant Candida [PMID: 28482886]
• Avoid fluconazole initially: Critically ill, unknown susceptibility, delayed fungicidal activity
• Consider fluconazole step-down: If C. albicans confirmed susceptible, patient stable, vasopressors weaned

B. Source Control (1 mark)

• Remove central venous catheter (right IJ) immediately [PMID: 28493856]
• Send catheter tip for culture
• Re-site new catheter at different site if required (prefer left IJ)

C. Adjunctive Measures (1 mark)

• Continue broad-spectrum antibiotics until bacterial infection excluded
• Optimize glucose control (target 8-10 mmol/L)
• Assess for other sources of infection (abdominal, urinary)

3. Duration of Antifungal Therapy (2 marks)

• Minimum 14 days after first negative blood culture (draw at least 24 hours apart) [PMID: 28493856]
• AND resolution of clinical symptoms (afebrile, haemodynamically stable)
• AND resolution of immunosuppression (if applicable)
• Extension: If disseminated disease (endophthalmitis, endocarditis) → extend to 4-6 weeks minimum

4. Investigations for Disseminated Disease (3 marks, 1 mark each)

• Fundoscopy: Assess for Candida endophthalmitis (mandatory in all candidemia cases) [PMID: 28493856]
• Echocardiography: TTE or TEE to assess for Candida endocarditis (especially if murmur, embolic phenomena)
• Abdominal imaging: Ultrasound or CT to assess for hepatosplenic candidiasis (chronic disseminated candidiasis), intra-abdominal abscesses

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SAQ 2: Invasive Aspergillosis

Question (15 marks)

A 55-year-old female with acute myeloid leukaemia (AML) is admitted to ICU with fever and respiratory failure. She completed induction chemotherapy 14 days ago and has been neutropenic (ANC below 100 cells/μL) for 10 days. She was started on broad-spectrum antibiotics (meropenem, vancomycin) 5 days ago for persistent fever. Over the past 24 hours, she has developed worsening dyspnoea, haemoptysis, and increasing oxygen requirements (FiO₂ 0.6).

Clinical Details

• Medical history: AML (M4 subtype), no prior invasive fungal infections
• Medications: Meropenem, vancomycin, prophylactic fluconazole 400 mg daily
• Vital signs: HR 120/min, BP 110/65 mmHg, RR 24/min, SpO₂ 92% on 6 L O₂
• Laboratory: WBC 0.5 × 10⁹/L (ANC 0), Hb 85 g/L, platelets 25 × 10⁹/L, CRP 180 mg/L
• Blood cultures: Negative (×3 sets)
• CT chest: Multiple pulmonary nodules (1-2 cm) with surrounding ground-glass opacity (halo sign), wedge-shaped peripheral infarcts

Questions

1. What is your differential diagnosis for the CT findings? List TWO diagnoses. (2 marks)
2. What are the key diagnostic tests you would order to confirm invasive aspergillosis? (4 marks)
3. Describe your immediate antifungal therapy, including specific agents and dosing. (5 marks)
4. What is the expected duration of antifungal therapy for invasive aspergillosis? (2 marks)
5. List TWO risk factors for this patient developing invasive aspergillosis. (2 marks)

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Model Answer

1. Differential Diagnosis for CT Findings (2 marks, 1 mark each)

• Invasive pulmonary aspergillosis: Halo sign (nodule with ground-glass halo) is characteristic of early angioinvasion [PMID: 26887756]
• Other invasive fungal infections: Mucormycosis (can present with similar nodules, though halo sign less specific), other mould infections (Fusarium, Scedosporium)

2. Diagnostic Tests for Invasive Aspergillosis (4 marks, 1 mark each)

• Bronchoscopy with BAL: Obtain BAL for galactomannan, culture, cytology, histopathology [PMID: 26887756]
• Galactomannan: Serum galactomannan (≥0.5 ODI positive) AND BAL galactomannan (≥1.0 ODI positive) - BAL more sensitive
• Beta-D-glucan: Pan-fungal marker (positive ≥80 pg/mL), supports diagnosis but non-specific
• Tissue biopsy: If accessible, obtain lung tissue for histopathology (septate hyphae with 45° branching) and culture

3. Immediate Antifungal Therapy (5 marks)

A. First-Line Therapy (3 marks)

• Voriconazole: First-line for invasive aspergillosis [PMID: 29362222]
  • "Loading dose: 6 mg/kg IV q12h ×2 doses (rapid therapeutic levels)"
  • "Maintenance dose: 4 mg/kg IV q12h (switch to PO 200 mg q12h when stable and tolerating oral intake)"
  • "Therapeutic drug monitoring: Target trough 1-5.5 mg/L (optimal 2-5 mg/L) [PMID: 26552889]"
  • "Rationale: Voriconazole superior to amphotericin for survival (71% vs 58%), fewer adverse events"

B. Alternative Agents (1 mark)

• Isavuconazole: 200 mg IV/PO loading q8h ×6 doses, then 200 mg daily (if voriconazole contraindicated or intolerant)
• Liposomal amphotericin B: 3-5 mg/kg/day IV (if voriconazole contraindicated or resistant)

C. Adjunctive Measures (1 mark)

• Discontinue fluconazole: Ineffective against Aspergillus, consider switching to prophylactic posaconazole after treatment
• G-CSF: Consider for persistent neutropenia (filgrastim 5 μg/kg/day SC) to accelerate neutrophil recovery
• Reduce immunosuppression: If feasible, reduce corticosteroids

4. Duration of Antifungal Therapy (2 marks)

• Minimum 6-12 weeks: Guided by clinical, radiological, and mycological response [PMID: 29362222]
• Clinical response: Resolution of fever, haemoptysis, respiratory symptoms
• Radiological response: CT chest showing improvement (decrease in nodule size, resolution of halo sign, cavitation indicates immune reconstitution)
• Mycological response: Negative galactomannan (serum and BAL), negative cultures
• Consider secondary prophylaxis: Lifelong prophylaxis (posaconazole) if ongoing immunosuppression (e.g., allogeneic HSCT)

5. Risk Factors for Invasive Aspergillosis (2 marks, 1 mark each)

• Profound neutropenia: ANC below 100 cells/μL for greater than 10 days (highest risk factor) [PMID: 29509985]
• Fluconazole prophylaxis: Provides no protection against Aspergillus, may select for resistant organisms
• Underlying haematologic malignancy: AML with induction chemotherapy (bone marrow suppression)
• Prolonged antibiotic exposure: Broad-spectrum antibiotics disrupt normal flora
• Corticosteroids: May have been administered during chemotherapy

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Viva Practice Questions

Viva 1: Candidemia Indications and Treatment

Examiner

"Good morning. I'd like to discuss invasive fungal infections in the ICU. Let's start with a clinical scenario."

Scenario "A 40-year-old male with acute pancreatitis undergoes pancreatic necrosectomy. On postoperative day 7, he develops fever (38.8°C) and hypotension requiring vasopressors. He has a left subclavian central venous catheter for TPN. Blood cultures show Candida glabrata."

Questions

Q1: What are the risk factors for candidemia in this patient?

Candidate "The key risk factors include:

1. Broad-spectrum antibiotics: He's likely received multiple antibiotics for pancreatitis and postoperative infections
2. Central venous catheter: Left subclavian CVC for TPN
3. Total parenteral nutrition (TPN): Major risk factor for candidemia
4. Abdominal surgery: Pancreatic necrosectomy with potential for gastrointestinal translocation
5. Critical illness: Postoperative ICU stay, organ dysfunction

Additional risk factors would include prolonged ICU stay (greater than 7 days), diabetes mellitus, renal replacement therapy, and immunosuppression." [PMID: 28493856, 27678912]

Q2: How would you manage this patient's candidemia?

Candidate "My management would involve three key components: antifungal therapy, source control, and assessment for disseminated disease.

A. Antifungal Therapy (First-line)

Given that this patient is critically ill with C. glabrata (a species with higher fluconazole MICs and emerging echinocandin resistance), I would start an echinocandin as first-line therapy [PMID: 28635507]:

• Caspofungin: 70 mg IV loading dose, then 50 mg IV daily
  • Alternatively, micafungin 100 mg IV daily or anidulafungin 200 mg IV loading, then 100 mg daily
• Rationale for echinocandin:
  1. Critically ill patient with haemodynamic compromise
  2. C. glabrata has reduced susceptibility to fluconazole
  3. Broad spectrum including azole-resistant Candida
  4. Excellent safety profile with minimal drug-drug interactions
  5. Evidence shows echinocandins have reduced mortality compared to azoles in ICU patients [PMID: 28482886]

B. Source Control

• Remove the central venous catheter immediately [PMID: 28493856]
  • Documented removal reduces duration of fungemia and improves survival
  • Send catheter tip for culture
  • Re-site new catheter at different site if required (prefer right IJ)

C. Assessment for Disseminated Disease

• Fundoscopy: Assess for Candida endophthalmitis (1-5% of candidemia cases)
• Echocardiography: TTE or TEE to assess for Candida endocarditis (0.4-1.6% of candidemia)
• Abdominal imaging: Ultrasound or CT to assess for hepatosplenic candidiasis (especially relevant given his recent pancreatic surgery)

D. Adjunctive Measures

• Continue broad-spectrum antibiotics until bacterial infection excluded
• Optimise haemodynamic support (vasopressors, fluids)
• Monitor for antifungal toxicity (LFTs with echinocandins, renal function with amphotericin if used)
• Consider surgical consultation for source control (drainage of intra-abdominal collections)"

Q3: What is the duration of therapy and when would you consider step-down therapy?

Candidate

"Duration of Therapy

Minimum 14 days after:

1. First negative blood culture (draw at least 24 hours apart)
2. Resolution of clinical symptoms (afebrile, haemodynamically stable)
3. Resolution of immunosuppression (if applicable)

Step-Down Therapy

I would consider step-down to fluconazole if:

1. Patient is clinically stable and improving (afebrile, off vasopressors)
2. C. glabrata susceptibility confirmed as fluconazole-susceptible
3. No evidence of deep-seated infection (negative endophthalmitis, endocarditis, hepatosplenic candidiasis)

If fluconazole-resistant or persistent fungemia, I would continue echinocandin for at least 14 days from first negative blood culture, or switch to liposomal amphotericin B if echinocandin-resistant.

For deep-seated infections (endocarditis, osteomyelitis, hepatosplenic candidiasis), duration is extended to 4-6 weeks minimum." [PMID: 28493856]

Q4: How do you interpret beta-D-glucan and galactomannan in this patient?

Candidate

"Beta-D-Glucan

• Positive (≥80 pg/mL single test or ≥60 pg/mL ≥2 consecutive tests) supports invasive candidiasis
• Sensitivity 70-90%, specificity 80-90%
• Useful for early diagnosis, monitoring response to therapy
• False positives: β-lactam antibiotics (especially piperacillin-tazobactam), haemofiltration, gauze packs, albumin, immunoglobulins

Galactomannan

• Negative in this case - galactomannan is Aspergillus-specific, not helpful for candidemia
• If positive, would suggest invasive aspergillosis (≥0.5 ODI serum, ≥1.0 ODI BAL)
• False positives: β-lactam antibiotics (piperacillin-tazobactam), certain foods (pasta, cereals), cross-reactivity with other fungi (Fusarium, Histoplasma)

In this patient, I would obtain baseline beta-D-glucan and monitor serially (2-3 times per week) to assess response to therapy. Galactomannan would not be helpful given Candida infection." [PMID: 26552889, 26887756]

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Viva 2: Invasive Aspergillosis Diagnosis and Treatment

Examiner

"Now let's discuss invasive aspergillosis. I'll present a different scenario."

Scenario "A 25-year-old male with acute lymphoblastic leukaemia (ALL) undergoes allogeneic HSCT. On day +45, he develops fever (39.2°C), cough, and dyspnoea. He is on prednisone 20 mg daily for GVHD. Chest CT shows a 2 cm right upper lobe nodule with surrounding ground-glass opacity (halo sign)."

Questions

Q1: What are the risk factors for invasive aspergillosis in this patient?

Candidate "The significant risk factors include:

1. Allogeneic HSCT: Highest risk group for invasive fungal infections, especially aspergillosis
2. GVHD requiring corticosteroids: Chronic GVHD with prednisone 20 mg/day significantly increases risk
3. Prolonged immunosuppression: Immune reconstitution delayed, impaired T-cell function
4. Time post-transplant: Late-onset invasive fungal infections (greater than 3 months) common in GVHD
5. Previous antifungal prophylaxis: May have received fluconazole (ineffective against Aspergillus) or posaconazole (possible breakthrough infection if resistance)

Other risk factors include CMV reactivation, neutropenia, and prior invasive fungal infection." [PMID: 28563456, 29509985]

Q2: What is the significance of the CT findings, and how would you diagnose invasive aspergillosis?

Candidate

"CT Chest Findings

• Halo sign: Nodule with surrounding ground-glass halo is characteristic of early angioinvasion in invasive pulmonary aspergillosis [PMID: 26887756]
• Timing: Halo sign appears early (0-5 days), indicating active infection
• Prognostic significance: Presence of halo sign suggests high fungal burden, poorer outcome if not treated promptly

Diagnostic Approach

According to EORTC/MSG diagnostic criteria, I would classify this patient as having probable invasive aspergillosis based on:

1. Host factor: Allogeneic HSCT with GVHD (chronic immunosuppression)

2. Clinical criterion: CT chest with halo sign

3. Mycological criteria (pending):

   A. Galactomannan Testing

   • Serum galactomannan: ≥0.5 ODI positive (sensitivity 70-90%, specificity 80-90%)
   • BAL galactomannan: ≥1.0 ODI positive (higher sensitivity than serum)
   • Serial monitoring: Check 2-3 times per week to assess response

   B. Beta-D-Glucan

   • ≥80 pg/mL positive (pan-fungal, less specific)
   • Supports diagnosis but cannot identify specific fungus

   C. Bronchoscopy with BAL

   • BAL for culture (sensitivity 30-50%, specificity 100%)
   • Cytology for fungal elements
   • Consider transbronchial biopsy if feasible

   D. Tissue Biopsy

   • Gold standard for proven invasive aspergillosis
   • Histopathology: Septate hyphae with dichotomous branching at 45° angle
   • Culture for species identification and susceptibility

Diagnostic Classification

• Proven: Tissue biopsy with hyphae OR positive culture from sterile site
• Probable: Host factor + clinical criterion + mycological criterion
• Possible: Host factor + clinical criterion (no mycology) OR host factor + mycology (no clinical)

In this patient, with positive CT findings and pending mycology, I would initiate empiric antifungal therapy while awaiting galactomannan results." [PMID: 26887756]

Q3: What is your first-line antifungal therapy, and how would you monitor response?

Candidate

"First-Line Antifungal Therapy

Voriconazole is first-line for invasive aspergillosis [PMID: 29362222]:

• Loading dose: 6 mg/kg IV q12h ×2 doses (rapid therapeutic levels)
• Maintenance dose: 4 mg/kg IV q12h
• Oral step-down: 200 mg PO q12h (when stable and tolerating oral intake)
• Therapeutic drug monitoring (TDM): Target trough 1-5.5 mg/L (optimal 2-5 mg/L) [PMID: 26552889]
  • Check baseline TDM at day 3-5 (steady-state)
  • "Adjust dose: If below 1 mg/L, increase dose; if greater than 5.5 mg/L, decrease dose"
  • Weekly monitoring thereafter

Rationale for Voriconazole

1. Proven mortality benefit vs amphotericin B (71% vs 58% at 12 weeks)
2. Better safety profile (fewer nephrotoxicity, infusion reactions)
3. Oral bioavailability (allows step-down therapy)
4. Excellent lung penetration (critical for pulmonary aspergillosis)
5. Superior to other azoles (itraconazole, fluconazole) for Aspergillus

Alternative Agents

• Isavuconazole: 200 mg IV/PO loading q8h ×6 doses, then 200 mg daily (if voriconazole contraindicated or intolerant)
• Liposomal amphotericin B: 3-5 mg/kg/day IV (if voriconazole contraindicated or resistant)

Combination Therapy Consider voriconazole + echinocandin (caspofungin or anidulafungin) in:

• High-risk patients (GVHD, neutropenia, high galactomannan greater than 2.0 ODI)
• Refractory disease despite monotherapy

Monitoring Response

1. Clinical: Fever curve, respiratory symptoms, haemodynamic status
2. Radiological: Repeat CT chest at 2-week intervals
   • Response: Decrease in nodule size, resolution of halo sign
   • Cavitation indicates immune reconstitution (good sign)
   • Worsening suggests treatment failure or resistance
3. Mycological: Serial galactomannan (2-3 times per week)
   • Decreasing levels indicate response
   • Persistent or rising levels suggest treatment failure
4. Laboratory: LFTs (voriconazole hepatotoxicity), electrolytes, renal function" [PMID: 27242914, 29362222]

Q4: What is the duration of therapy, and would you consider secondary prophylaxis?

Candidate

"Duration of Therapy

Minimum 6-12 weeks, guided by:

1. Clinical response: Resolution of fever, cough, dyspnoea
2. Radiological response: CT chest showing improvement (decrease in nodule size, resolution of halo sign, cavitation)
3. Mycological response: Negative galactomannan (serum and BAL), negative cultures
4. Immune reconstitution: Weaning corticosteroids, improving GVHD

Secondary Prophylaxis

Yes, I would strongly consider lifelong secondary prophylaxis in this patient:

Indications

• Allogeneic HSCT with chronic GVHD (ongoing immunosuppression)
• Prior invasive aspergillosis (high risk of recurrence if prophylaxis stopped)
• Expected prolonged immunosuppression (corticosteroids for GVHD)

Regimen

• Posaconazole 300 mg PO/IV daily (first-line for secondary prophylaxis) [PMID: 28563456]
  • "Alternative: Voriconazole 200 mg PO q12h (if previously treated successfully)"
  • Monitor trough levels (posaconazole greater than 1 mg/L, voriconazole 2-5 mg/L)

Duration

• Continue indefinitely while immunosuppressed
• Consider discontinuation only if immune reconstitution sustained (off immunosuppression for greater than 6-12 months)

Rationale

• High recurrence rate (50-70%) without prophylaxis in high-risk HSCT recipients
• Posaconazole reduces invasive fungal infections by 60-70% in high-risk patients
• Lifelong prophylaxis improves survival in allogeneic HSCT with chronic GVHD

Monitoring

• Regular clinical review (symptoms, fever)
• Serial galactomannan (if rising, consider breakthrough infection)
• Therapeutic drug monitoring
• Drug-drug interactions (posaconazole increases calcineurin inhibitor levels, reduce dose by 50-75%)"

---

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