Emergence of High-level Gentamicin Resistance among <i>Enterococci</i> Clinical Isolates from Burn Patients in South-west of Iran: Vancomycin Still Working

Abstract

<i>Enterococcus faecalis</i> and <i>Enterococcus faecium</i> are among the main agents associated with nosocomial infections with high mortality in immunocompromised patients. Antibiotic resistance, especially against gentamicin and vancomycin among <i>Enterococci</i>, is a risk factor that could increase the morbidity and mortality rate. 179 <i>Enterococci</i> isolates from burn patients were included in this study. Antibiotic susceptibility testing was done using the disk diffusion test and minimum inhibitory concentration (MIC) was evaluated by agar microdilution. Vancomycin and gentamicin resistance associated genes including <i>vanA</i>, <i>vanB</i>, <i>vanC</i>, <i>aac (6’)-Ie aph(2’’), aph(3’)-IIIa</i> and <i>ant(4’)-Ia</i> were detected by PCR and their statistical relation with antibiotic resistance was evaluated. <i>E. faecalis</i> was the more prevalent strain among our local isolates and showed a higher antibiotic resistance in comparison to <i>E. faecium</i>. Vancomycin had a good antibacterial effect on the <i>Enterococcus</i> spp. isolates; however, resistance to this antibiotic and a high-level gentamicin resistance (HLGR) phenotype were observed. Among <i>van</i> operon genes, <i>vanA</i> was the most prevalent gene and among the gentamicin resistance genes, <i>aph (3’)-IIIa</i> was more frequent. The HLGR <i>Enterococci</i> are a real challenge in nosocomial infections. Vancomycin is a key antibiotic to treat such infections but emergence of VRE in our region could be a real concern and, therefore, phenotypic and molecular surveillance must be considered.