MOLECULAR CHARACTERIZATION OF ESBL AND COLISTIN RESISTANCE GENES AMONG CLINICAL ISOLATES OF GRAM-NEGATIVE BACTERIA IN A TERTIARY HOSPITAL IN ABAKALIKI, NIGERIA

Antimicrobial resistance is a threat to public health. This study investigated the occurrence of ESBL and colistin resistance among Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa recovered from clinical samples (n=500) in a tertiary teaching hospital in Abakaliki, Nigeria. The samples were bacteriologically analyzed using selective culture media, biochemical tests, and PCR. All isolates were screened for ESBL and colistin resistance genes using both PCR and disk diffusion methods that included standard antibiotic disks for susceptibility studies. E. coli (n=173), K. pneumoniae (n=120) and P. aeruginosa (n=62) were recovered from the clinical samples investigated. The most prevalent ESBL genes detected is ^blaCTX-M found in 3 isolates of P. aeruginosa, 4 isolates of E. coli and 2 isolates of K. pneumoniae. The colistin resistance gene, mcr-3 was detected in 4 strains of E. coli for the first time in Southeast Nigeria. Both mcr-1 and mcr-3 was not detected in the K. pneumoniae strains. Only the mcr-2 colistin resistance genes were detected in K. pneumoniae strains. There was no detection of mcr-2 gene in the P. aeruginosa strains. Over 50% of the ESBL and colistin-resistant isolates showed high levels of reduced susceptibility to the tested antibiotics. Imipenem, to which all the ESBL and colistin-resistant isolates showed complete susceptibility (100%), followed by gentamicin (85%), were the most effective antibiotic against the ESBL and colistin-resistant isolates. Surveillance of ESBL and colistin-resistant bacteria in hospitals is important to mitigate the evolution and transmission of these multidrug resistant pathogens within the hospital and general environment.