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Many parts of pork meat processing are currently not used for human consumption in Switzerland, although they are of great nutritional value. Therefore, data on the occurrence of pathogenic organisms on byproducts is extremely scarce and the prevalence and population structure of Staphylococcus aureus on meat processing sidestreams is unknown. Hence, abattoir byproducts of pork origin including ear, forefoot, heart, intestine, liver, rib bone, sternum, bladder, stomach, hind foot and tongue originating from six abattoirs were screened for S. aureus. The obtained isolates were investigated by spa typing and DNA microarray analysis to reveal their genomic profile and population structure. The prevalence of S. aureus was generally low with a mean of 8%. In total, 40 S. aureus strains were detected and assigned to 12 spa types (t015, t1491, t1778, t091, t337, t899, t2922, t7439, t1333, t208, t4049, t034) and seven clonal complexes (CC1, CC7, CC9, CC30, CC45, CC49, CC398). Detected enterotoxin genes included sea, seb, sec, seh, sel and egc encoded toxin genes seg, sei, sem, sen, seo, and seu. None of the isolates harbored genes conferring methicillin resistance, but blaZ/I/R genes causing penicillin resistance were frequently found. In addition, strains from CC398 exhibited tetM and tetK, conferring tetracycline resistance. Similarity calculations based on microarray profiles revealed no association of clonal complexes with particular body parts, but revealed a certain correspondence of clonal complex and originating abattoir.

To assess the antimicrobial effect of a commercial steam-vacuuming system newly implemented after slaughtering, 105 cattle carcasses were examined for total viable counts (TVC) at four different areas. Before steam vacuuming, mean TVC of the excision samples were comparable at the perineal area and brisket (3.0-3.1 log CFU cm-2) or the hind leg and shoulder (2.6-2.7 log CFU cm-2). Steam vacuuming reduced mean TVC by 0.9, 0.7, 0.6, and 0.4 log CFU cm-2 at the perineal area, hind leg, shoulder, and brisket, respectively. With regard to the distribution of counts, steam vacuuming increased the proportion of TVC results <3.0 log CFU cm-2 from 74.8% (62.9-87.6% at carcass areas) to 86.7% (71.4-97.1% at carcass areas). Thus, steam vacuuming after slaughtering might be useful for the reduction of contamination in designated carcass areas, but the effect must not be overestimated and decontamination treatments always must be seen part of an integral food safety system.