A profile of vancomycin-resistant enterococcal infections and a comparison of resistance detection methods

Abstract

Scope: Vancomycin-resistant enterococci (VRE) are being increasingly reported from hospitals across the world. This study provides a profile of enterococcal infections and compares various methods of detecting vancomycin resistance. Materials and Methods: All clinically significant isolates of enterococci over a 2-year period were included. Antibiotic susceptibility was carried out as per CLSI guidelines. Vancomycin resistance was detected by 3 methods: disk diffusion, agar screen, E-test. The 3 methods were compared. Results: 156 clinical samples yielded Enterococcus spp. over the study period. Maximum resistance was noted to penicillin, erythromycin, and ciprofloxacin. E. faecium strains showed a higher percentage of resistance to the antibiotics tested. 15 (9.6%) enterococcal strains were resistant to vancomycin; 10 (6.4%) strains were intermediate. Compared to E-test, disk diffusion and agar screen had sensitivities of 100%. Disk diffusion had 97.2% specificity and agar screen demonstrated 92.9% specificity. Conclusion: Prevalence of VRE in Indian hospitals is increasing. Though disk diffusion had a higher specificity than the agar screen at identifying resistant isolates, intermediate strains were identified as sensitive. BHI agar containing 6 µg/ml of vancomycin can be used to screen for VRE, and E-test can be used to confirm resistance.

Comparison of different phenotypic methods for detection of Vancomycin Resistant Enterococci (VRE) among clinical isolates

“…Enterococcus faecalis was predominant among the other enterococcal isolates. 2,5 Nearly, 86.7% VRE isolates was observed in E. faecalis than E. faecium. 9 These two bacterial isolates showed highly resistance to Erythromycin, Clindamycin and Ampicillin antibiotics.…”

“…The results of antibiotics sensitivity testing were categorized based on the Enterococcus species (either Enterococcus faecium or Enterococcus faecalis) which are resistant to Vancomycin zone size ≤12mm. These isolates were screened for Vancomycin Resistant Enterococci (VRE) using Minimum Inhibitory Concentration (MIC) were compared with different methods viz., Agar dilution method, 2 Commercially available Vancomycin E Strip (HiMedia Laboratories, India) 9,11 and VITEK-2 automation system (BioMeriux, USA). 11,13,14,16 For agar dilution method, Muller Hinton broth were incorporated with Vancomycin was prepared in four different concentrations viz., 4µg, 8µg,16µg & 32µg per ml.…”

“…11,13,14,16 For agar dilution method, Muller Hinton broth were incorporated with Vancomycin was prepared in four different concentrations viz., 4µg, 8µg,16µg & 32µg per ml. 2,9 Vancomycin E Strip and VITEK-2 automation system were performed and the interpretation of the results reported based on the manufacturers' instructions.…”

“…Hence, they are difficult to treat because of multiple drug resistance to the various classes of antibiotics. 2 There are more than 40 species of the genus Enterococcus have been identified but some may have clinical importance to cause major infections in humans. Enterococcus faecalis and Enterococcus faecium plays a 90% of the infections in humans.…”

Microbiological investigation of ties and shirts in a Teaching Hospital, in São Paulo (SP), Brazil /Investigação microbiológica entre diferentes indumentárias em Hospital Escola em São Paulo (SP) Brasil

“…The emergence of this pathogen over the last two decades, among other factors, is in part due to its intrinsic resistance to commonly used antimicrobials. VRE (Vancomycin-Resistant Enterococci) (16) was not found on neckties, but a VRE colony was isolated from one of the shirt samples.…”