E-test versus disk diffusion method in determining multidrug resistant strains of Escherichia coli in urinary tract infection

Multidrug resistant strains of Escherichia coli are becoming a major challenge in treatment of patients with urinary tract infection. Developing effective screening methods for selection of antimicrobial resistant strains is necessary. In this study, we have compared descriptively results of E-test with Disk diffusion agar method in selection of multidrug resistant strains of E. coli among patients with urinary tract infection. In disk diffusion test, 19 of 256 urine collections were resistant to 5 antibiotics used in the study. Later E-test was performed on these 19 collections with the same 5 antibiotics. In E-test, 10.5% of the specimens were sensitive to Bacterim, 21.1% to gentamicin, 47.7% to nitrofurantoin, 10.5% to ciprofloxacin and 10.5% to Ceftazidime. Results indicate that performing E-test on strains that were resistant in disk diffusion test may increase specificity in determination of multidrug resistant strains of E. coli in patients with urinary tract infection. This antibiotic susceptibility study showed difference between E-test and disk diffusion agar in assessing the antibiotic susceptibility and found E-test accuracy and its superiority to disk diffusion in detecting multidrug resistance.