MOLECULAR EPIDEMIOLOGY OF CARBAPENEMASE GENES AMONG GRAM-NEGATIVE BACTERIA

ABSTRACT

As the scourge of antimicrobial resistance (AMR) continues to plague healthcare delivery limiting therapeutic options for patient care, reports of resistance to drugs of last resort such as carbapenems has been on the rise in Nigeria. This study therefore aimed at determining the prevalence of carbapenemase producing organisms (CPOs) as well as the molecular epidemiology of carbapenemase genes (KPC, OXA-48-like, VIM, NDM and IMP) among bacterial isolates recovered from clinical specimens in Benin City, Nigeria. A total of 451 consecutive, non-repetitive Gram negative bacterial isolates comprising 329 (72.9%) of Enterobacterales and 122 (27.1%) of nonfermenters were recovered from clinical specimens during the study period and identified using microbact 20E kit. Antimicrobial susceptibility tests were carried out on all isolates following Clinical Laboratory Standards Institute (CLSI) guidelines. Isolates that were resistant to the carbapenems (imipenem and meropenem), or were multi-drug resistant were screened phenotypically for carbapenemase-production using the simplified carbapenemase inactivation method and the combined disc synergy test. Carbapenemase-producing organisms (CPOs) were subsequently screened for carbapenemase genes (KPC, OXA48-like, NDM, VIM and IMP) using multiplex polymerase chain reaction (PCR) method. The prevalence of Gram-negative bacilli causing clinical infection was 14.9%. In comparison with outpatients, patients admitted to wards showed an increased likelihood of being infected with Escherichia coli (p = 0.0173) and Pseudomonas aeruginosa (p = 0.0222) than every other organism isolated. A total of 39 (8.7%) CPOs were detected using phenotypic method, 37 (92.5%) were confirmed using the PCR method. Isolates recovered from patients admitted to hospital wards were significantly more likely to harbor carbapenemase genes than those attending outpatient clinics.