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Stenotrophomonas on Meropenem — SCE Infectious Diseases MCQ

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ModerateAntimicrobial StewardshipStenotrophomonas on MeropenemSCE Infectious Diseases

A 55-year-old man on the ICU with ventilator-associated pneumonia has a tracheal aspirate growing Stenotrophomonas maltophilia. He is also on IV Meropenem for concurrent intra-abdominal sepsis. What adjustment is needed?

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Correct answer: D — Add IV or oral Co-trimoxazole for Stenotrophomonas coverage — Meropenem has no activity against S. maltophilia due to intrinsic resistance

S. maltophilia is intrinsically resistant to carbapenems (including Meropenem) due to L1 metallobeta-lactamase and L2 cephalosporinase production. Co-trimoxazole is the treatment of choice (the only reliably active agent). Alternatives include Ticarcillin/Clavulanate (limited availability), Levofloxacin, or Minocycline. Combination therapy may be considered for severe infections. Importantly, carbapenem use is a risk factor for selecting S. maltophilia — this organism often emerges during prolonged Meropenem treatment.

Reference: BSAC 2023 – MDR Gram-negative; EUCAST 2024 – Intrinsic resistance