Investigating the occurrence of different antibiotic resistance genes in Enterococcus faecalis and Enterococcus faecium isolates from burn patients in Ahvaz, southwest Iran

The aim of this study was to determine the prevalence of some antibiotic resistance genes in enterococci isolates collected from burn patients in Ahvaz, southwestern Iran. In this cross-sectional study, a total of 129 Enterococcus isolates were identified by biochemical and molecular methods. The antibiotic resistance patterns were determined using the disk diffusion method. The vancomycin susceptibility was determined by agar screen method. The distribution of vanA , vanB , aac(6′)-Ie-aph(2′′)-Ia , aph(2′′)-Ib , int1 , int2 , and int3 genes was investigated by polymerase chain reaction (PCR). Out of the 129 Enterococcus isolates, 74 (57.4%) and 55 (42.6%) were Enterococcus faecium and Enterococcus faecalis , respectively. Vancomycin resistance was found in a total of 28 (21.7%) Enterococcus isolates, including 16 (57.1%) E. faecium and 12 (42.9%) E. faecalis . Also, 2.7% ( n = 2/74) E. faecium and 1.8% ( n = 1/55) of E. faecalis isolates were extensively drug-resistant (XDR). Overall, vanA gene and vanB gene were detected in 79.1% ( n = 102/129) and 20.2% ( n = 26/129) of isolates, respectively. Among 55 E. faecalis isolates, 40 (72.7%) and 14 (25.5%) isolates were positive for vanA and vanB , respectively. Among 74 E. faecium isolates, 62 (83.8%) and 12 (16.2%) isolates were positive for vanA and vanB , respectively. In total, 102 (79.1%) isolates were suspected vancomycin-variable enterococci (VVE), which carried one of the van genes but were susceptible to vancomycin by agar screen method. Eighty-four (65.1%) enterococci species carried aac(6′)-Ie-aph(2′′)-Ia gene. The aac(6′)-Ie-aph(2′′)-Ia gene was detected in 50.9% ( n = 28/55) of E. faecalis and 75.7% ( n = 56/74) of E. faecium isolates, respectively. One hundred and three (79.8%) enterococci species carried aph(2′′)-Ib gene. The aph(2′′)-Ib gene was detected in 52.7% ( n = 29/55) of E. faecalis and 100.0% ( n = 74/74) of E. faecium isolates, correspondingly. Thirty-one (24.0%) enterococci isolates carried int1 gene. In total, 33.8% ( n = 25/74) of E. faecium and 10.9% ( n = 6/55) of E. faecalis isolates carried int1 gene. A total of 10 (7.8%) enterococci isolates carried int2 gene. Overall, 10.8% ( n = 8/74) of E. faecium and 3.6% ( n = 2/55) of E. faecalis isolates carried int2 gene. No isolates carried int3 gene. This study showed high frequency rates of multidrug-resistant E. faecalis and E. faecium harboring different resistance genes among burn patients in Ahvaz. The development of monitoring programs seems to be necessary to control the spread of these strains in the region.