Anti-Microbial Resistance of Enterococci Isolated from Urinary Tract Infections in Iran

Background: During the last decade, enterococci have become important nosocomial pathogens, representing the second leading cause of urinary tract infections. This increasing prevalence has been paralleled by the occurrence of multi-drug resistant (MDR) and high-level gentamicin resistant (HLGR) strains. Methods: From September 2005 to 2006, a total of 638 enterococcal isolates were collected from urine samples among 9 medical centers in Tehran (Iran). Confirmation of species and detection of gentamicin resistance genes were done by PCR method. Anti-microbial susceptibility test was determined with disk diffusion and minimal inhibitory concentration of gentamicin among HLGR isolates assayed by microdilution methods. Results: The isolates were found to consist of Enterococcus faecalis (77.8%) and Enterococcus faecium (22.2%). The results obtained from PCR showed a high rate of agreement with phenotypic assays for both species. MDR to most prevalent anti-microbials was present in 29% and 72% of the E. faecalis and E. faecium isolates, respectively. HLGR phenotype was detected in 64% of E. faecalis and 92% of E. faecium isolates. The aac(6')-Ie-aph(2")-Ia gene were identified in 83% of E. faecalis and 100% of E. faecium HLGR isolates. E. faecalis and E. faecium isolates differed in their susceptibilities to different antibiotics. Conclusion: Emergence of multi-resistant enterococci and high level resistance to gentamicin shown by enterococcal strains is of concern because of the decrease in the therapeutic options for treatment of infections caused by enterococci.