Frequency of Extended Spectrum Beta-lactamases Producing E. coli Strains Isolated from Urine of Inpatients in Yazd Hospitals and Detection of Resistance Pattern

Beta-lactamases are bacterial enzymes which cause hydrolysis of betalactam rings. Extended spectrum beta-lactamases cause bacterial resistance to penicillins, cephalosporins and aztreonam. Escherichia coli is a main cause of more than 80% of urinary tract infections. The aim of this descriptive-analytic study is to investigate the frequency of extended spectrum beta-lactamase in strains of E. coli separated from the urine specimens of inpatients in Yazd hospitals and to determine their sample of antibiotic resistance.
A total of 300 E. coli strains were isolated from the inpatients in Yazd Shohadaye-Kargar and Shahid-Sadouqhi hospitals during January 2014 to November 2015; and were identified by biochemical tests. Antibiotic susceptibility tests were performed by disk diffusion according to CLSI. Confirmatory combination disk method was used for detection of ESBLs, and SPSS 16 software was applied to analyze the data.
Out of 300 E. coli isolates, 111(37%) were identified as ESBL producer and 81(73%) were belonged to women and. Among ESBL producer isolates, the highest rate of resistance was related to Cefotaxime (100%), Ceftazidime (100%), Co-trimoxazole (89.2%), Nalidixic acid (81.1%), Ceftriaxon (62.2%), Ciprofloxacin (60.3%), Ofloxacin (60.3%), Norfloxacin (59.4%) and Gentamicin (42.3%) respectively.
The results showed that the frequency of ESBLs was 37% among E.coli isolates and regarding to the multidrug-resistant and ESBLs producing strains, it is suggested that if necessary, ESBLs phenotypic confirmatory test should be performed with susceptibility tests in the laboratories.