Frequency of erm A, B, C genes in Erythromycin resistant Enterococci isolated from Clinical samples of inpatients of Teaching Hospitals in Qazvin & Tehran

Enterococci are among the most important causes of urinary tract infections. The aim of this study was to assess the frequency of erm A, B, and C genes in erythromycin-resistant Enterococci isolated from the clinical samples of inpatients of university teaching hospitals in Qazvin and Tehran. From 2012 to 2013, a total of 165 samples of enterococci were isolated from the clinical samples of inpatients. Susceptibility to erythromycin in enterococci isolates was performed by agar dilution and disk diffusion methods according to the Clinical and Laboratory Standards Institute (CLSI) guideline. Erythromycin resistance genes (ermA, B, and C) were identified by PCR. Out of 165 clinical isolates of enterococci, 142 (86%) isolates were Enterococcus faecalis and 23 (13.9%) isolates Enterococcus faecium. The results of susceptibility test showed that 158 (% 95) isolates were resistant or with intermediate sensitivity to erythromycin. There was a good correlation between the results of disk diffusion and agar dilution methods. Of total samples, 147 (89%) isolates were resistant to erythromycin (MIC≥8 µg/ml), 11 (6.6%) isolates with intermediate sensitivity (MIC 1-4 µg/ml), and 7 (4.2%) isolates with complete sensitivity to erythromycin (MIC ≤ 0.5 µg/ml). The results of this study showed high prevalence of ermA, B, and C genes in erythromycin-resistant strains with ermB asthe most common resistance gene among these isolates.