Tuesday, 23 August 2011

MRSA in Canadian pigs, veterinarians and pork

In reports, currently being commented on in North America, but dating from a year ago, we encounter a new name for piggy MRSA: “Canadian epidemic MRSA” (CMRSA). 

We also get an unusually clear admission of the source of the problems in the discussion section.

At least the Canadians know they have problems, if not the true scale. 

In Britain, improbably, the government veterinarians still claim British pigs are clear of MRSA. 

They have not yet plucked up the courage to face the full brunt of public anger at the long standing deception. 

The whole report can be found here

Methicillin-resistant Staphylococcus aureus (MRSA) contamination of retail pork

Recent reports of isolation of methicillin-resistant Staphylococcus aureus (MRSA) from food animals 
have raised concern about the potential for foodborne transmission. This study evaluated the prevalence of MRSA  contamination of retail pork from 4 Canadian provinces...

....This study has determined that MRSA contamination of retail meat is not uncommon in Canada and is similar to that reported in other studies. While there was a significant difference in the prevalence between provinces, MRSA was found in pork products in every province. 

The reason for the difference in prevalence between provinces is unclear. Currently, the only study of MRSA in pigs in Canada involved farms in Ontario, and information about the prevalence of MRSA in pigs in other provinces is required to help interpret this finding.

The typing data were interesting and raise questions regarding the origin of contamination. The finding of PFGE nontypable spa 539/t034 MRSA, which has been previously identified as belonging to ST398, was expected as it is commonly reported in pigs internationally (4,6,10,20) and has been found in retail meat (11,12). It is reasonable to assume that ST398 contamination of meat is from pigs, either directly (deposition of MRSA  from the animal onto meat during slaughter) or indirectly (environmental contamination resulting in subsequent food contamination). 

However, since ST398 MRSA colonization rates of pig farmers and pig veterinarians are high (6,10,21), it is also possible that slaughterhouse workers have high colonization rates, and that those individuals could have been the source of contamination, even though they may have ultimately acquired MRSA from pigs...