Plazomicin activity against carbapenem-resistant Escherichia coli: A brief report

Carbapenem-resistant Escherichia coli (CR-E. coli) pose major therapeutic challenges. We evaluated the activity of plazomicin against 52 CR-E.coli isolates from a Mumbai tertiary hospital. Plazomicin demonstrated potent activity (Minimum Inhibitory Concentration [MIC] 0.19-2 mg/L) against isolates, including those harboring NDM or OXA-48-like carbapenemases, with or without aminoglycoside-modifying enzymes (AMEs). In contrast, isolates carrying 16S rRNA methyltransferases (RMTs) (e.g., rmtB1, rmtC, rmtF1) exhibited high-level resistance (MICs of ≥256 μg/mL). These findings not only highlight the advantage of plazomicin in AME-positive, RMT-negative strains, but also warn about the threat of emerging 16S RMT-mediated resistance that limit its clinical utility.