Plazomicin susceptibility profile in carbapenem-resistant Enterobacterales (CRE): a laboratory-based cross-sectional study from a tertiary care hospital in North India

BACKGROUND: Carbapenem-resistant Enterobacterales (CRE) represent a major therapeutic challenge, particularly in high-resistance settings where metallo-β-lactamases and aminoglycoside resistance mechanisms may coexist. Plazomicin, a next-generation aminoglycoside designed to evade many aminoglycoside-modifying enzymes, may retain activity against selected CRE isolates; however, its utility in Indian settings remains uncertain. OBJECTIVES: To evaluate the in vitro susceptibility of CRE isolates to plazomicin and compare its activity with conventional aminoglycosides, including amikacin, gentamicin, and netilmicin, with species-wise and phenotypic subgroup analysis. METHODS: This laboratory-based cross-sectional study included 106 non-duplicate CRE isolates from a tertiary care centre in North India. Isolates were analysed by specimen source, species distribution, plazomicin susceptibility, comparative aminoglycoside susceptibility, ceftazidime-avibactam (CZA) susceptibility, and ceftazidime-avibactam and aztreonam synergy testing. Statistical comparison of aminoglycoside susceptibility was performed, including paired analysis for Klebsiella pneumoniae using McNemar's exact test. Species-wise susceptibility was highest among Escherichia coli (16/27; 59.3%) and lower among Klebsiella pneumoniae (28/76; 36.8%). In K. pneumoniae, paired analysis showed significantly greater susceptibility to plazomicin (36.8%) than gentamicin (19.7%), amikacin (13.2%) and netilmicin (10.5%) with significantly higher paired susceptibility (McNemar exact p<0.001 for all comparisons). Among ceftazidime-avibactam (CZA) resistant, Aztreonam (AT) synergy-negative E. coli, 6/9 (66.7%) remained plazomicin-susceptible. CONCLUSION: Plazomicin demonstrated significantly greater in vitro activity than conventional aminoglycosides against CRE, but overall susceptibility remained limited. Its role in high-resistance Indian settings should be selective and guided by phenotypic susceptibility testing rather than empirical use.