RESUMEN
This study aimed to determine the prevalence of extended spectrum of beta lactamases [ESBLs], to compare different phenotypic methods for ESBL confirmation and to evaluate the antibiotic resistance patterns among ESBL-producing urinary Escherichia coli. Urinary E. coli isolates that were resistant to at least one of the three indicator cephalosporins [cefotaxime, cefpodoxime and ceftazidime] were tested for ESBL production using the double disc synergy test [DDST], the inhibitory potentiated disc diffusion [IPDD] test and the quantitative E-strip method. Of the 163 E. coli strains isolated, 80 [49%] were resistant to at least one of the three cephalosporins, and 38 [47.5%] tested positive for ESBLs by the IPDD test and the E-strip test. However, only15 [18.7%] strains tested positive by the DDST. Among the third-generation cephalosporins, cefpodoxime [46.1%] was the best screening indicator, followed by ceftazidime [43%] and cefotaxime [39.9%]. Most of the ESBL producers [97.3%] were resistant to three or more drugs, compared with 51.2% of non-ESBL producers. Compared with the DDST, the IPDD and E-strip tests appear to be preferable methods for detecting ESBLs, with better sensitivity [100%] and specificilty [97.6%] and positive predictive values [97.3%]. ESBL producers showed significantly [p < 0.05] higher resistance to tobramycin, co-amoxyclav and amikacin than did non-ESBL producers