Carbapenemase-mediated resistance in Acinetobacter baumannii clinical isolates: molecular epidemiology and antimicrobial potential of chitosan nanoparticles

Antibiotic resistance is an escalating global health concern, and Acinetobacter baumannii remains one of the most challenging multidrug-resistant pathogens. This study investigated the prevalence of key carbapenemase genes among clinical A. baumannii isolates and evaluated the antimicrobial potential of chitosan nanoparticles (Cs NPs) as an alternative therapeutic approach. Thirty-five clinical isolates were screened for blaOXA-51, blaOXA-23, blaNDM-1, blaIMP-1, and blaVIM-1 using colony PCR. Cs NPs were synthesized and characterized by XRD, FTIR, zeta potential, DLS, and TEM, and their antimicrobial activity was assessed using broth microdilution and electron microscopy. All isolates carried blaOXA-51, while blaOXA-23 and blaNDM-1 were detected in 80.0% and 45.7% of strains, respectively; blaIMP-1 and blaVIM-1 were absent. Cs NPs exhibited characteristic FTIR bands and an amorphous XRD profile, showed a narrow size distribution (~ 40 ± 2 nm), a zeta potential of + 35 ± 1 mV, and predominantly spherical morphology by TEM. They demonstrated strong antimicrobial activity, with MICs of 20–41.7 µg/mL and MBCs of 25–53.3 µg/mL, and TEM imaging revealed marked membrane disruption in treated cells. These findings highlight the high burden of carbapenemase genes in A. baumannii isolates and support Cs NPs as a promising antimicrobial candidate for combating this critical pathogen.