Vancomycin Resistant Enterococci (VRE)

• Reference Services
• Enterococcus Surveillance
• Periodicity of VRE in Canada
• Novel VRE Resistant Strains

• VRE Publications
• VRE Poster Presentations

An overview of the VRE  reference, surveillance and research activities of the ARNI Laboratory was recently presented at the ASM-FEMS International Conference on Enterococci in Helsigor, Denmark (Aug., 2005).  [Link to powerpoint presentation]

Reference Services

The ARNI lab provides VRE reference services to all hospital and public health laboratories across Canada. We require a pure isolate for testing. These tests are available upon request.

These activities include:

1. Identification of enterococci using classical microbiological methods and speciation using PCR to detect the ddl_faecium, ddl_faecalis, vanC1-3 genes.
2. Susceptibility testing to a variety of antimicrobials using agar dilution and/or Etest
3. PCR to detect the vancomycin resistance genes vanA, B, C, D, E, G.
4. Molecular strain typing for outbreak investigations using pulsed-field gel electrophoresis (PFGE) and/or multilocus variable number tandem repeat analysis (MLVA).
5. Characterization of unusual or rare resistance mechanisms to vancomycin, Linezolid, Synercid, or Ortavancin.
6. Disseminating novel resistance isolates to Canadian molecular laboratories for use as positive control strains.

The ARNI laboratory is prepared to develop any test necessary to meet an emerging problem related to antimicrobial resistance or a nosocomial outbreak investigation.

Enterococcus Surveillance

Initiated in 1998, surveillance for VRE is conducted in collaboration with the Canadian Nosocomial Infection Surveillance Program (CNISP) [LINK to CNISP].  This ongoing integrated surveillance program combines both epidemiologic and laboratory information to provide a comprehensive view of VRE across Canada.

Conly, J., M. Ofner-Agostini, S. Paton, L. Johnston, M. R. Mulvey, A. Kureishi, L. Nicholle, A. Matlow, The Canadian Epidimiology Committee, and The Canadian Nosocomial Infection Surveillance Program. 2001.  The emerging epidemiology of vancomycin-resistance in Canada: Results of the Canadian Nosocomial Infection Surveillance Program Passive Reporting Network 1994-1998.  The Canadian Journal of Infection Control. 16:71-80.

Rates of VRE have remained low in Canada over the last five years.

Periodicity of VRE in Canada

Interestingly, a periodic pattern of VRE has been reported with peak numbers occurring in the Spring.  This could be attributed to enhanced individual hospital surveillance activities at this time of year, or the influx of winter vacationers arriving back in Canada after spending the winter in warmer climates, or a combination of both.

 

Novel VRE Resistant Strains

Over the past several years, the ARNI lab has worked on the characterization of a number of novel molecular vancomycin resistance mechanisms in Enterococcus spp. in collaboration with laboratories across Canada.
Canada is the only country thus far to report all of the rare molecular types of vancomycin resistance. We believe this may be due to the large number of laboratories currently screening for the known genetic types encoding vancomycin resistance and the knowledge to forward strains with unusual or unidentified vancomycin resistant mechanisms to the ARNI laboratory for advanced characterization.

If you find a VRE with an unknown vancomycin resistance mechanism, please forward it to ARNI and we will collaborate with you to describe the molecular characteristics of the strain.

Once a novel VRE is characterized, we distribute the strain (with permission) and PCR protocols to molecular testing laboratories across Canada to ensure they can detect these unusual forms of resistance.
Some recent examples of our work are detailed below:

• The first VanG-type VRE was submitted to the NML in 2002 as part of the CNISP VRE surveillance project. Sequence analysis revealed it was 99 % identical to the previously reported vanG1 gene in E. faecalis strains identified in Australia. In addition we have identified an E. faecalis harbouring a variant of VanG-type resistance, VanG2, that was not detected with the existing vanG PCR primer sets as described in the published literature. These two studies have been published recently.

Boyd, DA, T. Du, R. Hizon, B. Kaplen, T. Murphy, S. Tyler, S. Brown, F. Jamieson,  K. Weiss, MR. Mulvey, and the Canadian Nosocomial Infection Surveillance Program. 2006.  VanG-type vancomycin resistant Enterococcus faecalis isolated in Canada.  Antimicrobial Agents and Chemotherapy. 50:2217-2221.

• Using the universal vanD primers as well as sequence analysis, we have identified a VanD variant, labelled VanD6. The E. gallinarum strain had a MICs of 256mg/L and 16 mg/L to vancomycin and teicoplanin, respectively.

Boyd, DA, M. A. Miller, and M. R. Mulvey. E. gallinarum N04-0414 harbors a VanD-type vancomycin resistance operon and does not contain a D-alanine:D-alanine 2 (ddl2) gene. Antimicrobial Agents and Chemotherapy. 50:1067-70

• We have identified a variant of VanD-type resistance in an E. faecium that we have termed VanD5. It was not detected with the existing published vanD PCR primer sets. This strain, as well as the sequences of a new ‘universal’ vanD PCR primer set, has been distributed to labs in Canada currently conducting PCR to detect VRE.

Boyd, D.A., P. Kibsey, D. Roscoe, and M.R. Mulvey on behalf of the Canadaian Nosocomial Infection Surveillance Program (CNISP). 2004. Enterococcus faecium N03-0072 carries a new VanD-type vancomycin resistance determinant: characterization of the vanD5 operon. J. Antimicrob. Chemother. 54:680-683.

• We have reported on the VanE form of vancomycin  resistance, the second report of this type of resistance world-wide.  The E. faecalis had a vancomycin MIC =  24 µg/mL and a teicoplanin MIC = 0.5 µg/ml

Boyd, D., T. Cabral, P. Van Caeseele, J. Wylie, and M.R. Mulvey. 2002.  Molecular characterization of the vanE gene cluster in vancomycin-resistant Enterococcus faecalis N00-410 isolated in Canada.  Antimicrobial Agents and Chemotherapy. 46:1977-1979.