Background: New Delhi metallo-β-lactamase (NDM)-producing Klebsiella pneumoniae poses significant risks, particularly for Egyptian pediatric patients who frequently use carbapenems without adequate diagnostic resources. The presence of efflux pump genes like OqxAB exacerbates antimicrobial resistance. This study investigated NDM variants, efflux pump genes, and molecular characteristics of blaNDM-5-positive K. pneumoniae in pediatric patients in Egypt.

Methods: Fifty-six K. pneumoniae isolates underwent carbapenemase testing via modified carbapenem inactivation methods (mCIM). Minimum inhibitory concentrations (MIC) for meropenem and colistin were determined, and PCR was used to detect resistance genes (blaCTX-M, blaNDM, blaKPC, mcr1, mcr2) and efflux pump genes (oqxA, oqxB). Sequencing of blaNDM and plasmid analyses were conducted. Efflux pump activity in blaNDM-5-positive isolates was assessed using carbonyl cyanide 3-chlorophenylhydrazone (CCCP), and horizontal gene transfer was evaluated through liquid mating assays.

Results: revealed 29 isolates with blaNDM-1, 9 with blaNDM-5, and 15 with blaKPC. MIC values for meropenem were higher in blaNDM-5-positive isolates compared to blaNDM-1. Additionally, 38 isolates were positive for blaCTX-M, and 15 for mcr1. Efflux pump genes OqxA and OqxB were detected in 26 isolates, while others had either gene independently. All but one blaNDM-5-positive isolate successfully transferred plasmids via conjugation. Plasmid replicon typing indicated that the FII plasmid group predominated in blaNDM-5 isolates.

Conclusion: This is the first report of highly resistant blaNDM-5-producing K. pneumoniae in Egyptian pediatric patients. The findings emphasize the urgent need for robust infection control and a national antimicrobial stewardship plan to combat the risk of horizontal gene transfer and increased resistance to carbapenems.