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.

RESULTS

Among 106 CRE isolates, most were from respiratory specimens 60/106; 56.6%), followed by blood (23/106; 21.7%). Overall, plazomicin susceptibility was 41.5% (44/106), higher than gentamicin (26.4%), amikacin (19.8%), and netilmicin (18.9%), with a statistically significant overall difference (χ2 = 17.80, df = 3, p = 0.00048). 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.