Methicillin-Resistant Staphylococcus aureus (MRSA)

• MRSA Reference Services
• MRSA Surveillance
• MRSA Research
• Biofilms and MRSA

• MRSA Publications
• MRSA Poster Presentations

MRSA Reference Services

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

These activities include:

1. Identification of MRSA using classical microbiological methods and molecular methods using real-time PCR multiplex to detect mecA/nuc/PVL multiplex.
2. Susceptibility testing to a variety of antimicrobials using broth microdilution and/or Etest.
3. Molecular strain typing for outbreak investigations using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, and spa typing.
4. Maintenance of a national database of over 10,000 MRSA fingerprints generated using PFGE.
5. Staphylococcal cassette chromosome (SCC) mec typing.
6. Characterization of unusual or rare resistance mechanisms to vancomycin, Linezolid, Synercid, or Ortavancin.
7. Staphylococcal toxin testing using PCR to detect genes encoding enterotoxins, exfoliative toxins, toxic shock syndrome toxin, and Panton-Valentine leukocidin toxin.

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

MRSA Surveillance

Canadian Nosocomial Infection Surveillance Program (CNISP)
Initiated in 1995, surveillance for MRSA is conducted in collaboration with the Canadian Nosocomial Infection Surveillance Program (CNISP) cnisp.ca .  This ongoing integrated surveillance program combines both epidemiologic and laboratory information to provide a comprehensive view of MRSA across Canada.

Simor AE, Ofner-Agostini M, Gravel D, Varia M, Paton S, McGeer A, et al.  2005. Surveillance for methicillin-resistant Staphylococcal aureus in Canadian hospitals – a report update from the Canadian Nosocomial Infection Surveillance Program.  Canadian Communicable Disease Reports. 1:33-40. 

Ofner-Agostini M., A. E. Simor, M. Mulvey, E. Bryce, M. Loeb, A. McGeer, A. Kiss, S. Paton,  and the Canadian Nosocomial Infection Surveillance Program, Health Canada. 2006. Methicillin-Resistant Staphylococcus aureus (MRSA) in Canadian Aboriginal People.  Infection Control and Hospital Epidemiology. 27:204-207.

Simor A. E., M. Ofner-Agostini, S. Paton, A. McGeer, M. Loeb, E. Bryce, M. Mulvey, and the Canadian Nosocomial Infection Surveillance Program (CNISP). 2005. Clinical and Epidemiologic Features of Methicillin-Resistant Staphylococcus aureus (MRSA) in Hospitalized Elderly Adults.  Infection Control and Hospital Epidemiology. 26:838-841.

Simor, A. E., M. Ofner-Agostini, E. Bryce, A. McGeer, S. Paton, M. R. Mulvey, and The Canadian Nosocomial Infection Surveillance Program, Health Canada. 2002.  Laboratory Characterization of Methicillin-Resistant Staphylococcus aureus in Canadian Hospitals: The Results of Five Years of National Surveillance 1995-1999.  Journal of Infectious Diseases. 186:652-660.

CNISP is also focusing on community-associated MRSA through an enhanced surveillance project.  Potential CA-MRSA cases, as determined by an infection control practitioner, are forwarded to the ARNI lab to be rapidly processed using PFGE and PCR to confirm MRSA and detect the PVL toxin.

There are currently 10 epidemic strains identified in Canada using PFGE fingerprints. Below are the characteristics of these isolates and how they relate to other known epidemic strains world-wide:

 

Case-Control Study for Community-Associated MRSA

The Northern Antimicrobial Resistance Partnership (NARP) is a Canadian Institutes for Health Research (CIHR) funded project to study antimicrobial resistance and usage in northern areas of Saskatchewan. www.narp.ca
CA-MRSA has been identified as a problem in regions of Saskatchewan.
To better understand the risk factors for acquisition of CA-MRSA in these regions a case control study has been undertaken.
A detailed explanation of the case-control study which is currently underway can be found by following the link.Case Control MRSA (Word)

Community-Associated MRSA in Canada

CMRSA7 - the CMRSA7 epidemic strain (pattern 0142) strain is indistinguishable to the USA400 strain (S. aureus MW2 Minnesota and North Dakota outbreak strain)[6], [7], [8].  We have seen PVL positive and negative CMRSA7 (pattern 0142) strains in Canada.  Patterns in the CMRSA7 group have been found to be either PVL positive or negative.

CMRSA10 - the CMRSA10 epidemic strain (pattern 0473) is indistinguishable to a pattern associated with multiple community-associated MRSA outbreaks in the United States (USA300)[1], [2], [3], [4] and has caused outbreaks in western Canada primarily in IV drug users and correctional facilities[5]. We have seen the 0473 pattern in Canada 167 times since the year 2000. All of the CMRSA10 (pattern 0473) strains that we have tested thus far are PVL positive, however not all patterns in the CMRSA10 group are PVL positive.

Southwest Pacific (SWP)/USA1100 strain - By comparison with recent publications, PFGE pattern 0524 in the national database looks to match the Southwest Pacific (SWP)/USA1100 strain.  The SWP strain has been associated with multiple community-associated MRSA outbreaks worldwide[4], [9]. These strains have been well documented as being ST30, PVL positive strains.  We have seen the 0524 pattern in Canada 4 times since the year 2001.

European CA-MRSA strain - Pattern type 0534 in the national database is indistinguishable to a pattern obtained from the European CA-MRSA strain10.  These strains have been documented as ST80, PVL positive strains. We have seen the 0534 pattern in Canada 4 times since the year 2001.

References

1. Centers for Disease Control and Preventions. 2001. Methicillin-resistant Staphylococcus aureus skin or soft tissue infections in a state prison, Mississippi, 2000. Morb. Mortal. Wkly. Rep. 50:919-922.
2. Centers for Disease Control and Preventions. 2003. Public health dispatch: outbreaks of community-associated methicillin-resistant Staphylococcus aureus skin infections,  Los Angeles, California, 2002-2003. Morb. Mortal. Wkly. Rep. 52:88.
3. Seybold, U, et al. 2006. Emergence of community-associated methicillin-resistant Staphylococcus aureus USA300 genotype as a major cause of health care-associated blood stream infections.  Clin. Inf. Dis. 42:647-656.
4. Tenover FC, et al. 2006. Characterization of a strain of community-associated methicillin-resistant Staphylococcus aureus widely disseminated in the United States. J. Clin. Microbiol. 44:108-118.
5. Main, CL, et al. 2005. Outbreaks of infection caused by community-acquired methicillin-resistant Staphylococcus aureus in a Canadian correctional facility. Can. J. Infect. Dis. Med. Microbiol. 16:343-348.
6. Hunt, C. et. al. 1999. Four pediatric deaths from community-acquired methicillin-resistant Staphylococcus aureus- Minnesota and North Dakota, 1997-1999. Morb. Mortal. Wkly. Rep. 48:707-710.
7. Mulvey, MR, et. al. 2005. Community-associated methicillin-resistant Staphylococcus aureus, Canada. Emerg. Inf. Dis. 11:844-850.
8. Wylie, JL and DL Nowicki. 2005. Molecular epidemiology of community- and health care-associated methicillin-resistant Staphylococcus aureus in Manitoba, Canada. J. Clin. Microbiol. 43:2830-2836.
9. Robinson DA, et al. 2005. Re-emergence of early pandemic Staphylococcus aureus as a community-acquired methicillin-resistant clone. Lancet 365:1256-1258.
10. Faria NA, et al. 2005. Epidemiology of emerging methicillin-resistant Staphylococcus aureus (MRSA) in Denmark: a nationwide study in a country with low prevalence of MRSA infection. J. Clin. Microbiol. 43:1836-1842.

MRSA Research

Methods Development

1. In collaboration with the Saskatchewan Public Health Laboratory, we have developed a multiplex real-time PCR assay to identify S. aureus (nuc) that harbours the methicillin resistance gene (mecA). The test also detects a toxin which has been associated with CA-MRSA strains (PVL). Publication McDonald JCM, 2005 #5
2. We are currently collaborating with Dr. Gilmour at the National Microbiology Laboratory to develop a simple Luminex-based assay to rapidly identify over a dozen Staphylococcal toxins.

Insights into the “Epidemic Nature” of MRSA
A graduate student is currently using DNA microarrays representing the entire genetic content of the COL strain to compare the gene content of Canadian epidemic MRSA strains to sporadic MRSA isolates.  We currently have a manuscript in preparation.

Below are a couple of presentations given involving these studies.

Christianson, S., M. R. Mulvey.  A Comparative Genomic Hybridization Study of Methicillin Resistant Staphylococcus aureus in Canada.  The 1st Annual Public Health Agency of Canada (PHAC) Research Forum.   Fort Gary Hotel, Winnipeg, MB.  March 20 – 21, 2006. 

Christianson, S., M. R. Mulvey.  Comparative Genomic Hybridizations of Hospital and Community-Associated MRSA in Canada.  45th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), Washington, DC, December 16 – 19, 2005.

Biofilms and MRSA

We are currently collaborating with Dr. S. Jones at the University of Calgary to study the ability of the identified Canadian epidemic MRSA (CMRSA) strains to form biofilms. Microarray data generated in the CGH study above will be linked to the ability of strains to form biofilms. Additional studies into gene expression in planktonic and biofilm growth will be studied.