Molecular detection of vanA and vanB genes among vancomycin-resistant enterococci in ICU-hospitalized patients in Ahvaz in southwest of Iran Mojtaba Moosavian,1,2 Hosein Ghadri,2 Zahra Samli3 1Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 2Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 3School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Objective: Nosocomial infections due to vancomycin-resistant enterococci (VRE) are known as a source of spreading these bacteria. The aim of this prospective study was molecular detection of vanA and vanB genes among VRE isolated from patients admitted to intensive care units (ICUs) in Ahvaz in southwest of Iran.Materials and methods: Overall, 243 non-duplicate rectal swab specimens were collected from ICU-hospitalized patients in teaching hospitals affiliated to Ahvaz Jundishapur University of Medical Sciences, Iran. The specimens were inoculated on suitable culture media, and isolates were identified by standard biochemical tests. The susceptibility and resistance of enterococci to 10 antibiotics were determined based on the Clinical and Laboratory Standards Institute guidelines. Resistance to vancomycin was phenotypically detected by vancomycin screening test, and the vanA and vanB genes in vancomycin-resistant isolates were amplified by multiplex PCR method.Results: Of 175 specimens containing enterococci, 129 (73.7%) isolates were detected as Enterococcus faecium and Enterococcus faecalis and 46 (26.3%) isolates as Enterococcus spp. The results of susceptibility test showed high rates of resistance to tetracycline, erythromycin, ciprofloxacin, and ampicillin. Moreover, based on this test, out of 129 Enterococcus isolates, 56 (43.4%) were resistant to vancomycin and teicoplanin. Also, among 59 vancomycin-resistant or semi-susceptible isolates, vanA gene was detected in 54 (91.5%) isolates, while none of the isolates had vanB gene.Conclusion: According to the results of this study, to prevent the spread of vancomycin-resistant Enterococcus strains, especially in nosocomial infections, the susceptibility of isolates should be determined before vancomycin prescription. Keywords: Enterococcus faecalis, Enterococcus faecium, multiplex PCR, vancomycin