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MDR Pseudomonas Pneumonia — FRCA Final MCQ

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HardIntensive Care MedicineMDR Pseudomonas PneumoniaFRCA Final

A 58-year-old man on the ICU develops hospital-acquired pneumonia on day 8 of admission. He has received intravenous piperacillin–tazobactam for 5 days for an intra-abdominal infection. A good-quality respiratory sample grows Pseudomonas aeruginosa resistant to piperacillin–tazobactam, ceftazidime, ciprofloxacin and aminoglycosides, but susceptible to meropenem and colistin. He is haemodynamically stable, is not neutropenic, has normal renal function and has no beta-lactam allergy. After discussion with microbiology, which is the most appropriate definitive antibiotic strategy?

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Correct answer: A — Stop piperacillin–tazobactam and give susceptibility-directed intravenous meropenem monotherapy

The correct answer is A. Definitive treatment should follow the susceptibility result: meropenem is an active systemic beta-lactam licensed for severe hospital-acquired pneumonia. Its dose and infusion strategy should be optimised for illness severity, renal function and the organism’s MIC according to microbiology advice. Piperacillin–tazobactam and ciprofloxacin are inappropriate because resistance is documented. Colistimethate is a less desirable systemic alternative because of nephrotoxicity and neurotoxicity and should be reserved for infections lacking a suitable conventional agent. Routine addition of nebulised colistimethate is not justified when an effective systemic beta-lactam is available; its UK inhaled indication is chronic Pseudomonas infection in cystic fibrosis, and evidence does not establish a clinical-outcome benefit from routine combination therapy in this setting.

Reference: NICE. Pneumonia: diagnosis and management (NG250), sections 1.5 and 1.7, 2025, updated 2026. https://www.nice.org.uk/guidance/ng250/chapter/recommendations