Molecular Characterization of Cocarriage Carbapenemase Genes in Clinical Pseudomonas aeruginosa
Abstract
Background Pseudomonas aeruginosa is a major nosocomial pathogen associated with multidrug resistance and limited treatment options. Carbapenem resistance mediated by carbapenemase genes is an increasing threat, yet molecular epidemiological data from Bangladesh remain scarce. Objectives To determine the prevalence of carbapenem resistance and carbapenemase genes, characterize cocarriage of carbapenemase determinants, evaluate phenotypic and molecular detection methods, and identify factors associated with carbapenem‐resistant P. aeruginosa. Methods A cross‐sectional study was conducted from January to December 2023 at a tertiary‐care teaching hospital in Chattogram, Bangladesh. Clinical specimens from 335 hospitalized patients were cultured, yielding 48 PCR‐confirmed P. aeruginosa isolates. Antimicrobial susceptibility testing was performed using CLSI guidelines. Carbapenemase production was assessed by modified carbapenem inactivation method (mCIM). Multiplex PCR was used to detect blaNDM, blaVIM, blaKPC, blaOXA‐48, and blaIMP genes. Selected amplicons underwent Sanger sequencing and phylogenetic analysis. Results Among 48 isolates, 27.1% were resistant to meropenem and 14.6% to colistin. Carbapenemase genes were detected in 20 (41.7%) isolates, with blaNDM being the predominant determinant (22.9%). Three isolates exhibited cocarriage of carbapenemase genes, including blaNDM+blaKPC, blaNDM+blaVIM, and blaNDM+blaOXA‐48. Phenotypic testing identified carbapenemase activity in 14 isolates, whereas six additional gene‐positive isolates were missed by mCIM. Phylogenetic analysis demonstrated close relatedness of detected carbapenemase genes to globally circulating variants. Conclusions Carbapenem resistance in P. aeruginosa is substantial in Bangladesh and is driven predominantly by blaNDM. The detection of isolates carrying multiple carbapenemase genes highlights the growing complexity of antimicrobial resistance. Combining molecular and phenotypic approaches can improve surveillance, infection control, and antimicrobial stewardship in resource‐limited settings.