Preliminary evaluation of good sampling locations on a pig carcass for livestock-associated MRSA isolation

Abstract

The presence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in livestock animals, especially in pigs, gave rise to concerns of pork being a possible MRSA source to the human population. Monitoring the flow-through of LA-MRSA throughout the meat production chain could be useful. Here, the optimal sampling location for LA-MRSA isolation on pig carcasses was determined. In one slaughterhouse, 40 cooled carcass halves from one LA-MRSA-positive herd were sampled on six carcass sites (ham, belly, back, forelimb, sternum and abdominal cavity). The obtained MRSA isolates were characterized using Pulsed Field Gel Electrophoresis. Without enrichment of the samples, no MRSA was isolated from the carcasses. After enrichment, MRSA was isolated from 19 out of 40 (47.5%) carcasses. The forelimb appeared to be the most contaminated part of the carcass (17/19 carcasses). Three pulsotypes were detected and the predominant pulsotype was also the herd pulsotype that was determined in our previous study. The present study demonstrated that the forelimb is a good sampling location for LA-MRSA. For good determination of LA-MRSA on carcasses, enrichment is needed. Only LA-MRSA was isolated. Moreover, the farm strain was isolated from the carcasses, which indicates that transmission from the primary production throughout the slaughterhouse occurred. The results suggest that good hygiene practices in slaughterhouses are important to reduce the transmission of LA-MRSA to the human population.