Phenotypic and molecular characterization of selected multiple antibiotic resistant clinical gram-negative bacteria from Obafemi Awolowo University teaching hospital, Ile-Ife, Nigeria
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Date
2024
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Department of Microbiology, Faculty of Science, Obafemi Awolowo University, Ile-Ife.
Abstract
This study identified Gram-negative bacilli from patients’ clinical isolates at Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife and determined the antibiotic susceptibility profile of the isolates. It detected the production of extended spectrum beta-lactamase in the multiple antibiotic-resistant (MAR) isolates, assessed the presence of selected antibiotic resistance and virulence genes in the MAR isolates, and determined the degree of genetic relatedness among the predominant multiple antibiotic-resistant strains. These were with a view to characterizing Gram negative bacilli isolated from some patients at the Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife. Three hundred and fifty presumed Gram-negative bacterial isolates were obtained from the Microbiology Laboratory at OAUTHC, Ile-Ife. The bacterial isolates were preliminarily identified by standard cultural, morphological and biochemical techniques. Further identification was performed using the Microbact™ GNB 24E identification kit. Antibiotic susceptibility testing (AST) was carried out using the Kirby-Bauer disks diffusion technique and interpreted according to the Clinical and Laboratory Standard Institute standards. The multi-antibiotic resistance index (MARI) was calculated. Phenotypic detection of extended spectrum beta-lactamase (ESBL) producing isolates was performed by the Double Disc Synergy test (DDST). Molecular detection of ESBL, antibiotic resistance and virulence genes in phenotypically confirmed ESBL-producing isolates was carried out by Polymerase Chain Reaction (PCR). Three hundred and fifty Gram-negative bacilli belonging to ten bacterial species were confirmed. Antibiotic susceptibility profile revealed that the isolates were sensitive to imipenem (82%) and nitrofurantoin (40%). However, the isolates showed high resistance to ciprofloxacin, ceftazidime, gentamicin, and ofloxacin. Thirty-six (10.3%) of the isolates had a multiple antibiotic resistance index (MARI) of 1.0. One hundred and thirteen (32.2%) of the isolates were phenotypically confirmed as ESBL-producers namely E. coli (n=46; 41.8%), Klebsiella pneumoniae (n=36; 29.5%), Pseudomonas aeruginosa (n=14; 36.1%), and Enterobacter sp (n=2; 9.1%). Prevalence of ESBL producers was significantly higher than non ESBL-producers in terms of resistance to ceftazidime (p= 0.004), ciprofloxacin (p= 0.012) and gentamicin (p= 0.034). Forty (35.4%) isolates harboured blaTEM. There was a concomitant carriage of two (blaCTX-M / blaSHV, blaSHV / blaTEM) or three (blaCTX-M / blaSHV / blaTEM) resistance genes by some of the isolates. The occurrence of virulence factors in the selected E. coli isolates include St1 (16.7%), Stx1 (10%), bfpA (6.7%) and aggR (13.3%). The phylogenetic evolutionary relationship of the selected isolates, identified three different clusters of Gram-negative bacilli namely E. coli, K. pneumoniae and P. aeruginosa.
This study concluded that the prevalence of clinical Gram-negative bacilli (E. coli, K. pneumoniae and P. aeruginosa) with multiple antibiotic resistance phenotypes (MARI above 0.3) and harbouring antibiotic resistance genes including multiple beta lactam resistance genes were significantly present in various samples at the OAUTHC, Ile-Ife.
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xx, 184p.
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Citation
Aliu, O. O. (2024). Phenotypic and molecular characterization of selected multiple antibiotic resistant clinical gram-negative bacteria from Obafemi Awolowo University teaching hospital, Ile-Ife, Nigeria. Department of Microbiology, Faculty of Science, Obafemi Awolowo University, Ile-Ife.