Prevalence and Characterization ofStaphylococcus aureusin Retail Raw Minced Meat

Abstract

Between April and October 2005, 120 raw minced meat samples comprising 40 pork, 40 beef, and 40 chicken samples purchased from 40 supermarkets in Hyogo (n=20) and Osaka (n=20) prefectures were examined for contamination with Staphylococcus aureus. The rate of isolation was 75.0% (30/40) for pork, 65.0% (26/40) for beef and 80.0% (32/40) for chicken meat. The most probable number (MPN) of the samples contaminated was widely distributed from 0.3 to>110/g. Seventy-nine (89.8%) of the positive samples had MPN values of less than 46/g. The majority of pork and beef isolates were classified as belonging to both human and K-β+CV: Abiotypes. Also, most chicken isolates belonged to both poultry and human biotypes. Seven (23.3%) of 30 pork isolates, 4 (15.4%) of 26 beef isolates and 9 (28.1%) of 32 chicken isolates produced one or two enterotoxins . Overall, the 20 enterotoxigenic isolates produced B (n=10), C (n=5), A (n=4) and AD (n=1). Enterotoxintype B was dominant in isolates from chicken meat. Eighty-two (93.2%) of the 88 isolates tested were differentiated into 8 coagulase types. All isolates except one (type I) were widely distributed from types II to VIII. Samples positive for S. aureus were detected in 38 of the 40 surpermarkets investigated. Interestingly, identical coagulase types, biotypes or enterotoxin types were found in isolates from all 2 or 3 kinds of meat samples retailed at te same supermarkets, indicating clonal spread of the same strain within meat-processing plants by cross-contamination.