Healthcare-Associated Infections — Clinical Case

DCE Long Case

Patient brief (provided to trainee)

Patient: Mr Robert Chen, 68 years old, retired mechanical engineer. [1]

Presenting complaint (current): On day 7 of his ICU admission, Mr Chen develops a new fever to 39.0 degrees Celsius, his white cell count rises to 18 x 10 to the 9 per litre, and his oxygen requirements increase from an FiO2 of 0.4 to 0.6. He has purulent respiratory secretions requiring frequent suctioning. [1]

Surgical history: Seven days ago, he underwent an emergency laparotomy for a perforated sigmoid diverticulum with generalised faecal peritonitis. He had a Hartmann procedure (sigmoid colectomy with end colostomy and rectal stump). He received piperacillin-tazobactam 4.5 g IV every 8 hours for 5 days postoperatively (ceased 2 days ago). Intra-operative cultures grew E. coli (susceptible to ceftriaxone, piperacillin-tazobactam, and meropenem) and Bacteroides fragilis. [1]

ICU course: He has been intubated and ventilated since admission for septic shock and respiratory failure. His vasopressor support (noradrenaline) was weaned on day 3. He has a triple-lumen central venous catheter in the right internal jugular vein (inserted on admission in the emergency department), a urinary catheter, and an arterial line in the right radial artery. His midline laparotomy wound is clean and dry. [1]

Current vital signs: Temperature 39.0 degrees Celsius, heart rate 108, blood pressure 110/65 (on no vasopressors), respiratory rate 24 (ventilated, synchronised intermittent mandatory ventilation), oxygen saturation 94 per cent on FiO2 0.6 and PEEP 8. [1]

Investigations on the current presentation:

• Full blood count: haemoglobin 105 g/L, white cell count 18 x 10 to the 9 per litre, platelets 220 x 10 to the 9 per litre.
• C-reactive protein 210 mg per litre (was 85 two days ago).
• Creatinine 120 micromoles per litre (baseline 90).
• Lactate 1.8 mmol per litre.
• Chest X-ray: new consolidation in the right lower lobe.
• Paired blood cultures (peripheral and through central line, drawn before antibiotics): both grow Pseudomonas aeruginosa. The central line culture turns positive 3 hours before the peripheral culture.
• Endotracheal aspirate: Pseudomonas aeruginosa (same sensitivity pattern as the blood culture).
• Urine culture: no growth. [1]

Past medical history: Type 2 diabetes (HbA1c 7.8 per cent), hypertension, hyperlipidaemia, ex-smoker (ceased 10 years ago, 40 pack-years). No known allergies. [1]

Social history: Lives with his wife. Two adult children who live locally. Retired 3 years ago. He was independent in activities of daily living before this admission. [1]

Candidate's structured presentation (model)

SASPOP opening statement: [1]

"Mr Robert Chen is a 68-year-old retired engineer with type 2 diabetes and hypertension, who is day 7 post an emergency Hartmann procedure for a perforated sigmoid diverticulum with faecal peritonitis, and who now presents with dual device-associated healthcare-associated infections — a Pseudomonas aeruginosa catheter-related bloodstream infection from his right internal jugular central line (confirmed by paired blood cultures with a differential time to positivity above 120 minutes) and a concurrent ventilator-associated pneumonia from the same organism grown from his endotracheal aspirate. He has been intubated since admission, received 5 days of piperacillin-tazobactam, and his underlying surgical condition is healing well with a clean wound." [1]

Structured problem list: [1]

1. Pseudomonas aeruginosa catheter-related bloodstream infection — confirmed CRBSI by paired cultures and DTP, requiring immediate line removal and targeted anti-pseudomonal therapy.
2. Concurrent Pseudomonas ventilator-associated pneumonia — late-onset VAP on day 7 of ventilation, same organism and sensitivity as the blood culture.
3. Prolonged ICU admission with ventilator dependency — 7 days of mechanical ventilation, with the risk of further device-associated complications, critical illness polyneuromyopathy, and deconditioning.
4. Recent broad-spectrum antibiotic exposure — 5 days of piperacillin-tazobactam, which likely selected for the Pseudomonas colonisation and infection, and which carries ongoing risks of C. difficile and further resistance.
5. The underlying surgical condition — perforated diverticulum with faecal peritonitis, post-Hartmann procedure; the wound is clean but I must exclude an ongoing or recurrent intra-abdominal source.
6. Type 2 diabetes and age — predispose to infection, require glycaemic control, and affect the recovery trajectory. [1]

Integrated management plan

1. Pseudomonas CRBSI — immediate line removal and targeted therapy: [1]

The central venous catheter must be removed immediately — Pseudomonas is NOT an organism for which salvage should be attempted. I remove the line, send the tip for semi-quantitative culture (Maki roll-plate), and insert a new central line at a different site (preferably subclavian, if no contraindications, to minimise infection risk) if ongoing central access is needed. The targeted therapy is an anti-pseudomonal beta-lactam to which the isolate is susceptible — based on the sensitivity results, I would use piperacillin-tazobactam 4.5 g IV every 6 hours (if the isolate is susceptible) or ceftazidime 2 g IV every 8 hours or cefepime 2 g IV every 8 hours. I would NOT add vancomycin (no Gram-positive infection) or an aminoglycoside (does not improve outcome in Pseudomonas bacteraemia and adds nephrotoxicity). The duration is 14 days from the first negative blood culture, with repeat blood cultures every 48 to 72 hours until clearance. If bacteraemia persists beyond 72 hours despite line removal and appropriate therapy, I would search for metastatic infection (echocardiography, CT imaging) [3].

2. Concurrent VAP — same targeted therapy and ventilator bundle: [1]

The VAP is caused by the same organism with the same sensitivity pattern, so the same targeted therapy covers both foci. I would send daily endotracheal aspirates to monitor the response. The duration for VAP is typically 7 days, but since this patient has concurrent bacteraemia, the 14-day course guided by blood culture clearance is the controlling duration. I apply the ventilator bundle to prevent further VAP and ventilator-associated events: head of bed elevation to 30 to 45 degrees, daily sedation interruption with a spontaneous breathing trial, oral chlorhexidine, subglottic secretion drainage (if the tube has the port), peptic ulcer prophylaxis, and DVT prophylaxis [4] [5].

3. Daily assessment for readiness to extubate: [1]

The single most effective VAP prevention measure is extubation. I conduct a daily sedation interruption with a spontaneous breathing trial to identify readiness for extubation as early as possible. The criteria are: the underlying condition is improving (surgery healing, infection treated), the patient is neurologically adequate (awake, cooperative, able to protect the airway), the gas exchange is adequate (PaO2 above 60 on FiO2 0.4 or below, PEEP 5 or below), and the patient passes a spontaneous breathing trial without respiratory distress [4].

4. Prevention of C. difficile: [1]

The patient has had 5 days of piperacillin-tazobactam and now faces 14 days of further anti-pseudomonal therapy — a significant antibiotic burden that predisposes to C. difficile infection. I would monitor for diarrhoea, send stool for C. difficile toxin if it develops, and minimise the antibiotic duration by de-escalating and stopping as soon as clinically indicated [6]. I would also consider whether the peptic ulcer prophylaxis (PPI) is still needed — prolonged PPI use is an independent risk factor for CDI.

5. Glycaemic control: [1]

As a diabetic patient with critical illness and infection, Mr Chen requires careful glycaemic control. I would use an insulin infusion protocol targeting blood glucose between 8 and 10 mmol per litre (avoiding both hyperglycaemia, which worsens infection outcomes, and hypoglycaemia, which is dangerous). I would monitor his blood glucose hourly on the insulin infusion and transition to his usual subcutaneous regimen when he is stable and eating. [1]

6. Exclusion of ongoing intra-abdominal source: [1]

Although the wound is clean and the initial surgery was successful, the development of Pseudomonas bacteraemia raises the question of whether there is an ongoing intra-abdominal source (abscess, anastomotic leak — though the Hartmann procedure has no anastomosis). If the patient does not improve with appropriate therapy, or if blood cultures remain positive despite line removal, I would order a CT abdomen with contrast to exclude an intra-abdominal collection or ongoing source. [1]

7. Nutritional support and rehabilitation: [1]

After 7 days of critical illness, Mr Chen is at risk of significant deconditioning and critical illness polyneuromyopathy. I would ensure adequate nutrition (enteral feeding via nasogastric tube, transitioning to oral as tolerated), involve the physiotherapist for early mobilisation (passive range of motion while ventilated, active mobilisation as he improves), and plan for rehabilitation once he is stable enough to leave the ICU. [1]

Examiner discussion questions

Q1: "His central line was inserted in the emergency department under time pressure. What are the key elements of the central line insertion bundle that should have been applied, and what is the evidence for the bundle?" [1]

"The central line insertion bundle has five components, all of which should be applied for every insertion regardless of the urgency: hand hygiene before the procedure; full barrier precautions (sterile gown, gloves, cap, and a full-body sterile drape for the operator and all assistants); chlorhexidine skin preparation (2 per cent chlorhexidine in 70 per cent alcohol, applied with friction and allowed to dry); avoidance of the femoral site in adults (the subclavian vein has the lowest infection rate, the internal jugular is intermediate, the femoral has the highest); and daily review of necessity with prompt removal of the line when it is no longer needed. [1]

The evidence is the landmark Pronovost Michigan ICU study, published in the New England Journal of Medicine in 2006, which implemented this five-component bundle across 103 ICUs in Michigan and reduced CLABSI rates from a median of 2.7 to 0 per 1000 catheter-days at 3 months, with a sustained reduction of up to 66 per cent at 18 months [1]. This is among the strongest evidence in all of inpatient medicine for a quality improvement intervention. The key insight is that the bundle is effective not because any single component is new, but because delivering all five reliably and together — supported by a checklist, a central-line cart with all supplies, and a culture where any team member can stop the procedure if a component is missed — transforms the safety of the procedure. The bundle should be applied in the emergency department just as in the ICU, and time pressure is not an excuse to omit it — the patient has the same infection risk regardless of where the line is inserted [2]."

Q2: "You mentioned that the preceding piperacillin-tazobactam exposure may have selected for the Pseudomonas. Explain this mechanism, and tell me how you would review the stewardship of the preceding course." [1]

"The mechanism is antibiotic selection pressure. Piperacillin-tazobactam is an anti-pseudomonal beta-lactam that disrupts the normal competitive flora of the oropharynx and gut, removing the colonisation resistance that normally limits Pseudomonas colonisation. Pseudomonas aeruginosa is an environmental organism that colonises healthcare environments (sinks, taps, respiratory equipment) and the oropharynx and gut of hospitalised patients, particularly those on broad-spectrum antibiotics. The antibiotic kills the susceptible competing flora and allows Pseudomonas — which may have intrinsic or acquired resistance — to overgrow. Once colonised, the patient is at risk of Pseudomonas VAP (from microaspiration of colonised oropharyngeal secretions) and Pseudomonas CRBSI (from hub contamination by the hands of healthcare workers carrying the organism, or from bacteraemia seeding the line). [1]

For the stewardship review, I would ask: was the initial piperacillin-tazobactam appropriate? For perforated diverticulum with faecal peritonitis, empiric broad-spectrum cover IS appropriate — this is the correct initial choice, covering the likely organisms (Enterobacteriaceae and anaerobes). Was it de-escalated when the intra-operative cultures returned? The cultures grew E. coli (susceptible to ceftriaxone) and Bacteroides fragilis — the appropriate de-escalation at 48 hours would have been to ceftriaxone plus metronidazole, which is narrower than piperacillin-tazobactam and does not have anti-pseudomonal activity. Was the duration appropriate? For complicated intra-abdominal infection with adequate source control (the Hartmann procedure is definitive source control), 4 days of therapy is adequate according to the STOP-IT trial — the patient received 5 days, which is at the upper end but not excessive. But the failure to de-escalate from piperacillin-tazobactam to a narrower regimen when cultures returned is a stewardship gap that likely contributed to the Pseudomonas selection pressure. This is the lesson: the 48-hour review with mandated de-escalation is the single most effective stewardship intervention, and it was not done in this case [6]."

Q3: "What is the role of subglottic secretion drainage in VAP prevention, and when would you use it?" [1]

"Subglottic secretion drainage (SSD) uses specially designed endotracheal tubes with a suction port located above the cuff, which continuously or intermittently removes the pooled oropharyngeal secretions that accumulate above the cuff and leak past it into the lower airway — the primary mechanism of microaspiration in VAP. The Muscedere meta-analysis of 13 randomised trials, published in Critical Care Medicine in 2011, showed a pooled relative risk of 0.55 for VAP, with additional reductions in duration of mechanical ventilation and ICU length of stay [5]. The number needed to treat is approximately 10 to 15 patients to prevent one VAP episode.

I would use subglottic suction endotracheal tubes for all patients who are expected to be intubated for more than 48 to 72 hours, which includes virtually all ICU patients intubated for septic shock or respiratory failure. For Mr Chen, if his current endotracheal tube does not have a subglottic suction port, I would NOT exchange the tube electively to get this feature — the risks of tube exchange (hypoxia, haemodynamic instability, aspiration, failed reintubation) outweigh the marginal benefit in a patient who is already receiving the other bundle components. But I would ensure that all new intubations in the ICU use subglottic suction tubes as the default, and I would review the unit's policy to ensure this is standard practice." [1]

Q4: "How would you prevent this patient from developing further device-associated infections during the remainder of his ICU stay?" [1]

"The prevention of further HAI in this patient rests on three principles: device minimisation, bundle reliability, and stewardship. For device minimisation, every device must have a documented daily indication and be removed as soon as it is no longer needed — this applies to the new central line (can he be managed with a peripheral line and a PICC?), the urinary catheter (can he use a bedpan or be catheterised intermittently?), the arterial line (is invasive blood pressure monitoring still needed?), and the endotracheal tube (extubate as soon as possible). The new central line should be managed with the ongoing bundle: chlorhexidine-impregnated sponge dressing, aseptic hub access (scrub the hub with chlorhexidine or alcohol before every access), daily review of necessity, and removal as soon as possible. [1]

For bundle reliability, I would ensure the ventilator bundle is applied consistently: head of bed elevation, daily sedation interruption, oral chlorhexidine, subglottic secretion drainage, and daily assessment for extubation readiness. I would also ensure reliable hand hygiene by all staff (WHO Five Moments), as cross-transmission on hands is the mechanism by which most HAI organisms spread. [1]

For stewardship, I would ensure the current antibiotic course is the minimum effective duration (14 days guided by blood culture clearance, then stop), that no unnecessary additional antibiotics are added (e.g., no empirical metronidazole for anaerobic cover if there is no evidence of intra-abdominal recurrence), and that the PPI prophylaxis is stopped when no longer indicated. Every antibiotic day carries a risk of C. difficile and further resistance selection, and minimising unnecessary exposure is itself a prevention measure [6]."

Q5: "His wife asks whether he picked up the infection because the hospital is dirty. How do you respond?" [1]

"I would respond honestly and without defensiveness. I would explain that healthcare-associated infections are unfortunately common in critically ill patients who need invasive devices like breathing machines and intravenous lines for prolonged periods, and that Mr Chen developed infections from two of his devices — the intravenous line and the breathing tube. I would explain that the bacteria that caused the infection (Pseudomonas) is a common organism in hospitals and is more likely to affect patients who have been very sick, on antibiotics, and in intensive care for some time. I would be honest that the broad-spectrum antibiotics he needed for his abdominal infection may have contributed by allowing the Pseudomonas to take hold, and that this is a recognised risk of necessary treatment. [1]

I would emphasise that the team is taking the matter seriously — we have identified the infections, we are treating them with the right antibiotic, we have removed the infected line, and we are applying all the measures we know to help him recover and to prevent further infections. I would NOT blame the hospital or imply negligence, but I would also NOT dismiss her concern — I would acknowledge it, explain the mechanisms clearly, and describe the concrete actions we are taking. I would offer to bring the intensivist and the infectious diseases specialist to a family meeting to discuss the plan in detail, and I would ensure the family has a clear point of contact for questions. The communication is part of the treatment — a family that understands what has happened and what is being done can support the patient and participate in decisions about the road ahead." [1]

Q6: "What quality improvement measures would you recommend to the ICU to reduce HAI rates?" [1]

*"I would recommend a comprehensive HAI prevention programme built on the evidence-based principles [1] [4]:

1. Surveillance and feedback: measure CLABSI, VAP, CAUTI, and CDI rates by month and by bed, with benchmarking against national data (CDC NHSN or equivalent), and report back to the clinical team monthly. Knowing the rates drives improvement. [1]

2. Central line insertion and maintenance bundle: implement the five-component insertion bundle with a checklist and a central-line cart; audit adherence; empower any team member to stop the procedure if a component is missed; use chlorhexidine-impregnated dressings; and conduct a daily review of line necessity on the ward round with mandatory removal of unnecessary lines. [1]

3. Ventilator bundle: implement the ventilator bundle (head of bed elevation, daily sedation interruption, oral chlorhexidine, subglottic secretion drainage, DVT and stress ulcer prophylaxis) with daily audit and feedback; use subglottic suction tubes for all expected prolonged intubations. [1]

4. Catheter removal protocols: implement nurse-driven urinary catheter removal protocols (remove the catheter unless a physician documents a reason to continue) and daily review of all device necessity. [1]

5. Hand hygiene programme: education, alcohol-based hand rub at every point of care, regular observation and feedback of adherence (target above 80 per cent), and a culture where healthcare workers hold each other accountable. [1]

6. Antimicrobial stewardship: pre-authorisation of restricted agents, mandatory 48-hour review with de-escalation, IV-to-oral switch protocols, facility-specific treatment guidelines, and a C. difficile surveillance programme. [1]

7. Outbreak response: a defined plan for identifying and investigating clusters, with environmental sampling, molecular typing, enhanced cleaning, cohorting, and communication. [1]

The single most effective intervention is reliable implementation of the central line and ventilator bundles with measurement and feedback — the Pronovost model showed that this approach can reduce CLABSI by up to 66 per cent and can be sustained over time [1]."*