Molecular Characterization of Extended Spectrum <i>β</i>-Lactamase Genes in Clinical <i>E. coli</i> Isolates

Abstract

Extended Spectrum Beta-Lactamases (ESBLs) encoding genes (TEM, SHV and OXA) were amplified from multidrug resistance E. coli. The multidrug resistance E. coli isolates from different clinical sources were documented to be plasmid encoded and resistance against β-lactam and cephalosporin. Conventional laboratory analysis showed that seventy percent (70%) of the selected multidrug resistant clinical isolates were ESBLs positive, showing a ≥5 mm increase in zone diameter for either antibiotics compared to its zone when tested alone. The antibiotic susceptibility result showed that 100% of the isolates were resistant to amoxicillin-clavulanic acid, amoxicillin, cefuroxime and ampicillin-sulbactam while 90% of the isolates were resistant to ceftazidine and tetracycline, 80% to ofloxacin, 70% to ceftriazon, nalidixic acid, cefalexin, 60% to ciprofloxacin, 50% to nitrofurantoin, 40% to chloramphenicol and 20% to gentamicine. The multiplex PCR with primers TEM (931bp), SHV (868), OXA-2 (478), aac(3)-IIa (900) and rmtA (634), which are genes responsible for extended spectrum β-lactamase and aminoglycoside resistance in E. coli shows that: isolate W15 comprises of three (3) resistant gene, which corresponds with TEM resolving as a 931 base pair, SHV 868 base pair, and a 478 bp indicating OXA-2 that is faint probably indicating a low concentration of the gene. Isolate B2 comprises single resistant gene, which is interpreted as OXA-2 with 478 base pair while isolate URO2, U64 and S45 comprises of two resistance genes which resolve as 868 and 478 base pair indicating SHV and OXA-2 respectively. However, isolates S57, U58 and B7 showed no gene amplification despite the various degree of resistance in MIC and antibiotic susceptibility profile test obtained with conventional detection analysis. We assume that their resistant genes are not coded for by the primers used in this study as these isolates are likely to contain other resistant genes, which are also expressed at a molecular level. This study stands to show that molecular characterization has a great correlation with analytical methods.