Generally, E. faecalis has been known as the major cause of enterococcal infections, 10 times more prevalent than other enterococcus species. However, in recent years a remarkable change has seen from E. faecalis to E. faecium probably because of the emergence of VRE strains among members of this species in hospital environments . The prevalence of E. faecium has been increased in Iranian hospitals during the last few years. In the present study, the ratio of infections due to E. faecalis to those caused by E. faecium was 1.2: 1 (51.3% versus 41.4%) which is still higher than some previous reports published from Iran and some other countries [4, 15, 16]. The increased ratio was supported by enhancement of VREfm strains. The emergence of E. faecium isolates with a high level of resistance to three main classes of antibiotics (i.e. glycopeptides, β-lactams and amino glycosides) against enterococci spp is a major concern in hospitals. Congruent with the results from the USA hospitals, all the studied VRE isolates in Iran are resistant to ampicillin, whereas European hospital-derived clones are reported to be vancomycin susceptible but resistant to ampicillin and gentamicin [17–19].
Our current study clearly shows that in Iran the frequency distribution of VRE is high compared to rest of the countries of the world [20–23]. Also, all of VRE isolates showed resistance to more than 6 antibiotics, 60% of VRE isolates showed threatening resistance phenotype to vancomycin, teicoplanin, ampicillin, gentamicin, ciprofloxacin, tetracycline, erythromycin, nitrofourantoin (Va/Tei/Am/Gm/Cip/Te/E//Ni). Moreover high MIC values (MIC50 ≥ 128) were also found for vancomycin and ampicillin as well as gentamicin MIC50 ≥ 1024.
It is also vibrant from the present study that all VRE isolates harbored vanA gene as describes previously. The wards related to kidney transplantation and nephrology, and ICU was estimated to be the ones with the highest risk of infection by VRE (Figure 2). The present study also reveals that linezolid and quinopristin- dalfopristin (synercid) were the most effective agents against the E. faecium isolates.
The dissemination of VREfm, studies conducted in Iranian hospitals have found the dominancy in polyclonal among clinical isolates instead of clonal spreading as reported in USA and Europe but has consistency with Saudi Arabian hospitals [7, 18–20].
The relative congruence of antibiotic resistance patterns and the specific PFGE patterns among the studied isolates demonstrates the presence of E. faecium strains with similar clone types in each of the hospitals e.g. pulsotypes C, H and L in hospital 1, pulsotype A in hospital 2, pulsotype I in hospital 3 and J in hospital 4 were identified.
The pulsotype patterns and resistance profiles suggest that there was an inter-hospital dissemination of pulsotype F and D (isolates were obtained from different sources and wards). Most of the other pulsotypes (e.g. Pulsotypes A, C and I) were related to the same hospitals. The best example for intra hospital dissemination was pulsotype C, because all of these strains were isolated from urine samples and from the same ward of a hospital.