Methicillin-resistant Staphylococcus aureus in retail pork

Abstract number: O94

Weese J.S., Reid-Smith R., Rousseau J., Avery B.

Objectives: Community-associated MRSA is an increasing problem and an association with food animal contact has been made in some regions. This has led to concerns about the potential role of food in MRSA transmission. The objective of this study was to evaluate the prevalence of MRSA colonisation of retail pork in Canada.

Methods: Pork chops, ground pork and pork shoulders were purchased at retail outlets in four Canadian provinces in conjunction with the Canadian Integrated Program for Antimicrobial Resistance Surveillance. Both direct inoculation of meat into enrichment broth and rinsing of meat in broth were performed for pork chops and shoulders, followed by inoculation onto Chromogenic agar. Ground pork was tested only using the direct method. MRSA isolates were typed by PFGE and spa typing. Real time PCR was used to detect Panton-Valentine leukocidin genes.

Results: MRSA was isolated from 31/402 (7.7%, 95% CI 5.5–10.7%) of samples. There was a significant difference between provinces (P < 0.001) but no difference between different products, with MRSA isolated from 23/296 (7.7%) pork chops, 7/94 (7.4%) ground pork and 1/12 (8.3%) pork shoulders (P = 0.99). 21/403 (5.2%) samples were positive using direct culture while MRSA was isolated from 15/355 (4.2%) of samples testing using the rinse method. Nine samples were positive on direct culture but negative using the rinse method, while 10 others were positive only with the rinse method and only 5 were positive with both methods. Seven samples (ground pork) that were positive on direct culture were not tested using the rinse method. 3 main clones were present. The most common (40% of isolates) was a group of 3 related spa types (t064, t008 and new related type) were classified as Canadian epidemic MRSA-5 by PFGE, an ST8 human epidemic clone that has been associated with horses. PFGE-non-typable spa t034 were not surprisingly common, accounting for 30% of isolates. The 3rd main group was 3 related spa types (t002, t045 and new type) that were CMRSA-2 (USA100), an ST5 clone that is common in humans in Canada, that also accounted for 30% of isolates.

Discussion: The clinical relevance of MRSA contamination of pork is currently unclear. It is possible that contact with contaminated food could be a mode of MRSA transmission in the community, although further study of the prevalence of contamination, amount of MRSA in contaminated samples, sources of contamination and implications on human health are required.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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