Detection of Van-Positive and Negative Vancomycin Resistant Entrococci and their Antibacterial Susceptibility Patterns to the Newly Introduced Antibiotics

Abstract

The aim of this study was to determine the types and frequencies of VRE in terms of the existence of Van genes and to investigate the efficacy of newly introduced antibiotics. Totally 297 enterococcal strains were isolated from patients' specimens. Minimum inhibitory concentration of resistant isolates to vancomycin and tecoplanin were determined by E test method. Simultaneous detection of Van genes and species identification was preformed using multiplex PCR. Sensitivity patterns of VRE isolates to several antibiotics were determined by disk diffusion (Kirby-Bauer) method. One hundred and four (35%) of the isolates were VRE of which 12.5, 10.5 and 7% from urine, blood and stool samples were detected, respectively. Resistant isolates were sensitive to tigecycline and linezolid and resistant to ciprofloxacin and amikacin. The isolates which were resistant to ciprofloxacin, amikacin and gentamicin also showed cross-resistance to the other tested antibiotics. VanA is the predominant gene of Van-positive isolates in Iran. Meanwhile, the prevalence of Van-negative intermediate VRE in E. fecalis is markedly increased. These findings lend support to the hypothesis that due to frequent vancomycin administration in our clinics the acquisition of Van genes as well as selection of resistant mutant isolates could be facilitated. Rational prescription of vancomycin and wisely administration of newly introduced antibiotics like tigecycline and linezolid is warranted.