Prevalence of extended spectrum βeta-lactamase producing Escherichia coli from patients diagnosed with urinary tract infections in Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State.

Abstract

Background: Extended spectrum Beta-lactamases (ESβLs) are variants of beta lactamase enzymes that are capable of hydrolyzing broader spectrum of beta-lactams antibiotics. The enzymes have mutation in the gene at the active site that is believed to be the cause of high Beta lactamase activity. ESβL mediate resistance to all third generation cephalosporins, including monobactams. This study was carried out to determine the prevalence of ESBL producing Escherichia coli from patients presenting with cases of urinary tract infection at Olabisi Onabanjo University Teaching Hospital between April and June 2016. Method: Urine samples from cases of UTI were centrifuged and the subnatants were diluted serially up to 10 5 with sterile distilled water. A loopful of each of the last two dilutions was streaked on a plate of sterile Eosin Methylene Blue (EMB) agar. The plates were incubated at 370C for 24 hrs. Plates that elicited growth were sub-cultured and stored for further use. Gram staining and conventional biochemical tests including indole, citrate utilization, hydrogen sulphide utilization, nitrate, catalase and urease tests were conducted on selected distinct colonies with green metallic sheen on the EMB culture plate. Antimicrobial susceptibility was determined by disc-diffusion method. ESBL detection was done by using the double-disc synergy test. An antibiotic disc of amoxicillin-clavulanic acid (Oxoid, UK) was placed at the center of the plate and discs containing Ceftazidime (CAZ - 30μg) (Oxoid, UK), Ceftriaxone (CRO - 30μg) Aztreonam (ATM - 30μg) were sited 0.2cm equidistant from the amoxicillin-clavulanic acid disc. After aerobic incubation at 37ºC for 18 hours, a clear extension of the edge of the growth inhibition zone of the cephalosporins towards amoxicillin-clavulanic acid disc was measured and used as positive index of ESβL production. Results: Of the 100 urine samples examined, 79 (79%) isolates of Escherichia coli were detected by conventional biochemical tests of which 30 (38%) isolates were found to exhibit ESβL production. The antibiotic susceptibility profile of the isolates elicited highest susceptibility to ofloxacin (90%), gentamicin (87%) and amoxicillin-clavulanate (53%). A progressive decrease in sensitivity to cefixime (60%) and cefuroxime (27%) – a cephalosporinase effect was recorded. Conclusion: Judicious use of antibiotics is more important to prevent infections by these resistant organisms in the community coupled with awareness by microbiologists and clinicians serving the community as key to early detection and appropriate treatment of patients affected by ESβL producing Escherichia coli.