Influence of pigskin on Salmonella contamination of pig carcasses and cutting lines in an Italian slaughterhouse

Abstract

Ninety pig carcasses and twenty one food contact surfaces (FCSs) were tested for <em>Salmonella</em> in a slaughterhouse processing <em>ca.</em> 380 pigs/h between 2014-2015. Sampling was performed during seven sessions. Four carcass sites of 100 cm² each (back, belly, jowl externally, and the diaphragmatic area internally) were swabbed after evisceration. Meat conveyors and dressing tables were tested swabbing areas of 200 to 400 cm². After pre-enrichment in buffered peptone water, samples were tested by <em>Salmonella</em> MDS^® assay and the presumptive positives were confirmed by the ISO 6579 method. <em>Salmonella</em> isolates were serotyped following the Kauffman- White-Le Minor scheme and genotyped by XbaI pulsed field gel electrophoresis. <em>Salmonella</em> was isolated from 16/90 [17.8%; confidence interval (CI) 95%=11.2-26.9] carcasses and 4/21 (19.0%; CI 95%=7.7-40.0) FCSs. Four serovars were identified on carcasses. <em>S. enterica</em> 4,[5],12:i:- was the most prevalent (43.75%), followed by <em>S.</em> Rissen (31.25%), <em>S.</em> Derby (12.5%) and <em>S.</em> Bovismorbificans (12.5%). Two serovars were found on FCSs, namely S. Derby (75%) and <em>S.</em> Livingstone (25%). During one sampling session, a failure in carcass dehairing occurred and caused significantly higher prevalence of carcass contamination (60%) than in the remaining sessions. Moreover, in the same session, <em>Salmonella</em> prevalence was marginally significantly higher on FCSs than in the remaining sampling days, suggesting that dehairing affects contamination not only on carcasses, but also on the working surfaces.