Diversity and Genetic Clonality of Vancomycin and Gentamicin Resistant Enterococci Isolated from Healthy Humans in Iran

Background: This study was done to determine the level of high level gentamicin resistant (HLGR) and vancomycin resistant enterococci (VRE) in the healthy normal human population living in Tehran, Iran. Methods: A total of 700 fecal samples were isolated from the period of September 2007 to September 2008 and the species were identified by the biochemical tests and PCR. Antibiotic susceptibility test, gentamicin and vancomycin resistant genes and the conjugation tests were performed to evaluate the transferability of the drug resistant genes. The clonality of the isolates was also determined by PFGE. Results: The results showed that the prevalence of HLGR and VRE in the healthy normal population were 16.6% (100) and 1% (6) for HLGR and VRE, respectively. Amongst the HLGR enterococci, the most frequent species were found to be Enterococcus faecalis in 63% of the isolates. This was followed by E. faecium (33%), E. gallinarum (3%) and E. casseliflavus (1%). The frequency of the gentamicin resistant genes were 99 (99%), 91 (91%), 3(3%) and 1(1%) for aac(6')-Ie-aph(2'')-Ia, aph(3')-IIIa, ant(4')Ia and aph(2'')-Id genes, respectively. Among the vancomycin resistant genes, vanA was found in 1% (6) of isolates only. PFGE revealed high heterogeneity among the 63 E. faecalis strains and 33 E. faecium with 31 and 28 different patterns, respectively. The 6 VR E. faecium revealed 6 different patterns. Conclusion: The prevalence and heterogenous populations of HLGR in the normal flora of the humans found here were higher than reports from many countries, may be suggestive of excessive antibiotic usage in Iranian