blaNDM-5 is the predominant variant of blaNDM gene in Klebsiella species detected in Mississippi, USA.

OBJECTIVES

The Mississippi Public Health Laboratory conducts active surveillance of carbapenem-resistant Enterobacterales (CRE) infections as part of the Antimicrobial Resistance Laboratory Network (ARLN) program implemented by the United States Centers for Disease Control and Prevention (CDC). Here, we describe the prevalence of New Delhi Metallo-β-lactamase (blaNDM) genes in Klebsiella, a major pathogen of the Enterobacterales order linked to nosocomial infections, between January 2022 and June 2025.

METHODS

Carbapenemase activity was confirmed using the Modified Carbapenem Inactivation Method (mCIM). PCR was then performed on carbapenemase-positive isolates to detect blaNDM genes. Whole-genome sequencing (WGS) was performed on 35 blaNDM-positive isolates to identify blaNDM gene variants, other antimicrobial resistance (AMR) determinants, virulence factors, and plasmids. Antibiotic susceptibility testing (AST) was determined by the Kirby-Bauer disk diffusion assay.

RESULTS

Among the 35 NDM-positive Klebsiella species, the blaNDM-5 variant was identified in 23 (65.7%) isolates, followed by blaNDM-1 and blaNDM-7 genes which were identified in 6/35 (17%) and 6/35 (17%) cases, respectively. A significant proportion of blaNDM-5 cases also harbored additional β-lactamase genes such as blaSHV family (18/23; 78%) and blaTEM-1 (9/23; 39%) indicating multi-drug resistance. All 23 blaNDM-5-positive isolates were resistant to carbapenems and broad-spectrum cephalosporins, but 13/23 (56.5%) remained susceptible to aztreonam. PlasmidFinder analysis identified IncX3 (20/23) and IncFIB(K) (19/23) as the predominant plasmid replicons among these isolates.

CONCLUSION

The emergence and spread of bacteria carrying blaNDM-5 gene poses a significant threat to public health in Mississippi. Our dataset warrants further study to investigate the potential role of plasmids in blaNDM-5 dissemination.