Abstract
BACKGROUND: Vancomycin-resistant enterococci (VRE) are resistant to most classes of antibiotics. Diagnosis of VRE using standard methods takes 2 to 5 days. Development of a rapid PCR-assay that detects and identifies resistant genes in bacteria would provide time-critical information on the presence of VRE in clinical samples allowing early treatment and management of infected patients.
OBJECTIVES: Investigate the use of high resolution melting analysis (HRMA) and 16S-rRNA-PCR approach for rapid and cost-effective identification of VRE.
DESIGN: Descriptive antibiotic susceptibility studies.
SETTING: Manchester Academic Health Sciences Centre and School of Translational Medicine, University of Manchester, UK, and Department of Clinical Laboratory Sciences, Taibah University, Saudi Arabia.
MATERIALS AND METHODS: PCR-HRMA using 16S-rRNA V1-primers was used to detect and identify VRE. DNA from different strains of vancomycin-resistant and -sensitive Enterococcus faecalis (VSE) and Enterococcus faecium were amplified using V1-primer followed by HRMA in a single run. Differentiation of VRE from VSE was based on curve shapes generated against reference organisms (Bacteroides fragilis).
MAIN OUTCOMES MEASURES: Amplification curves and difference plots for VRE and VSE.
RESULTS: Difference plots were generated for all vancomycin-resistant and -sensitive E faecalis and E faecium strains by subtracting their fluorescence melting profile from that of a reference-species B fragilis. A characteristic curve shape was produced by vancomycin-sensitive E faecalis and E faecium. However, vancomycin-resistant strains of these bacteria were associated with a markedly different curve shape facilitating a clear differentiation.
CONCLUSION: The 16S-PCR-HRMA approach has the potential for detecting vancomycin-resistant E faecium and E faecalis. Data with VRE provide the basis for combining VRE identification with pathogens speciation in a rapid, cheap assay able to identify a pathogen as an Enterococcus and whether it is vancomycin-sensitive or -resistant E faecium or E faecalis in a single PCR and HRMA run.
LIMITATIONS: Tested on specific, but not all, reference Enterococcus species and clinical isolates.