Phenotypic and Genotypic Characterization of Urinary Isolates Expressing an Extended- Spectrum Beta-lactamase

Abstract

Bacteria from clinical and non-clinical settings are becoming increasingly resistant to conventional antibiotics and broader infection-control problem. Patients admitted to hospitals for the treatment of resistant bacterial infections are adding to the already too high costs of healthcare and are a source of resistant bacteria and/or resistance-encoding genes. The aim of the study was to identify the genes (CTX-M, SHV and TEM) responsible for extended-spectrum beta- lactamase (ESBL) phenomenon among Gram negative bacteria isolated from Sudanese patients infected with urinary tract infection (UTI). Three hundred and thirty two (n=332) urine specimens were collected from patients attending different hospitals in Khartoum State during the period from May to November 2011. The isolates were identified by using conventional biochemical methods and microbact 2000 24E (OXOID) system. All Isolates were tested for their antimicrobial resistance. ESBL screening was confirmed by double disk synergy test and VITEK 2 system. Results showed that frequency rate of urinary Gram negative isolates was 218 (65.7%). The major isolate was E. coli 157 (72.0%), followed by K. pneumoniae 32 (14.7%). The maximum sensitivity was seen for imipenem (100%). The maximum resistance was seen against ceftazidime 163 (74.8%). ESBL producing bacteria was 130 (59.6%) and was mostly K. pneumoniae 22/32 (68.8%). ESBL producing bacteria showed maximum resistance to ceftazidime 124/130 (95.4%). ESBLs positive strains were tested for the presence of ESBL encoding genes using PCR with specific primers for the detection of CTX-M, SHV and TEM genes. The presence of CTX-M, SHV and TEM genes was confirmed in 68/130 (52.3%) of the isolates. The ESBL genes were detected in 19 Klebsiella strains and in 49 of Escherichia coli isolates. The genes detected were found to be carried by K. pneumoniae and Escherichia coli strains. ESBL was found to be higher in Sudan compared with other countries. Among urinary isolates the commonest prevalence ESBL gene was CTX-M gene followed by TEM; while the least one detected was SHV gene.