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Elizabethkingia Vancomycin Gram-Negative — SCE Infectious Diseases MCQ

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HardHealthcare-Associated InfectionsElizabethkingia Vancomycin Gram-NegativeSCE Infectious Diseases

A 55-year-old man develops a hospital-acquired bloodstream infection with an organism identified as Chryseobacterium (Elizabethkingia) meningoseptica. The microbiology registrar calls to highlight that this Gram-negative rod is unusually susceptible to Vancomycin. Why is this remarkable?

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Correct answer: B — Vancomycin is normally inactive against Gram-negative organisms (cannot penetrate the outer membrane); Elizabethkingia is one of the very few Gram-negative bacteria susceptible to Vancomycin — a classic microbiology teaching point

Elizabethkingia meningoseptica is a rare Gram-negative rod that is intrinsically resistant to most Gram-negative antibiotics (Carbapenems, Aminoglycosides, Colistin) but paradoxically susceptible to Vancomycin — an agent typically only active against Gram-positives. This is thought to be due to unique cell wall composition allowing Vancomycin access. Treatment: Vancomycin, Fluoroquinolones, Co-trimoxazole, or Rifampicin (based on susceptibility). This organism is the classic exam answer for 'Gram-negative susceptible to Vancomycin.'

Reference: BSAC 2023; EUCAST 2024; JCM 2020