Antibiotic Resistance Pattern and Identification of Vancomycin Resistance Genes in Enterococcus spp. Isolated from Environmental Samples in Southern Fars province

Enterococcus spp. are predominant in the faecal microflora which enter the environment directly or through wastewater. These bacteria play an important role in the development of nosocomial infections due to their ability to acquire resistance genes and their transmission to other bacteria, particularly Staphylococcus aureus. The aim of this study was to identify the prevalence of vancomycin-resistant enterococci (VRE) and to detect van A, van B and van C1/C2 genes in VRE strain isolated from environmental samples of the in southern Fars province.
This cross-sectional study was carried out on 155 Enterococcus spp isolates collected from environmental samples (hospital wastewaters and surface waters) in different areas of Larestan and Jahrom cities. Isolates were identified and confirmed as Enterococcus spp. using the membrane filtration method, selective growth on Kenner Fecal Streptococcus Agar (KF) medium and biochemical tests. The disk diffusion test and Macro Broth dilution method based on CLSI guidelines were used to determine antimicrobial susceptibility against conventional antibiotics and vancomycin and to measure the minimum inhibitory concentration (MIC), respectively. Finally, the presence of van A, van B and van C1/C2 genes in VRE strains was determined by multiplex PCR technique.
Out of all of Enterococcus spp. isolates, 41 cases (26.45%) were belonged to E.faecalis, 6 cases (3.87%) to E.faecium and 108 cases (69.68%) to non-faecalis and non-faecium. In total, 46 isolates (29.67%) were resistant to vancomycin and 4 isolates showed MIC ≥128 μg/ml. Resistant to all types of antibiotics was observed in 4 isolates (8.70%). Further, 2 isolates (50%) had vanA gene and 2 isolates (50%) had vanB gene, but vanC1/C2 genes were detected in none of them.
The results indicated that the VRE strains are widespread in the studied area, therefore there is an urgent need for prudent use of vancomycin and implementation of control measures to prevent the environmental spread of VRE strains.