Prevalence and classification of toxigenic Staphylococcus aureus isolated from refrigerated ready-to-eat foods (sushi, kimbab and California rolls) in Korea

Aims: To investigate the presence of toxigenic Staphylococcus aureus in ready-to-eat (RTE) Korean foods and determine the distribution of genes related to various types of toxin production. Methods and Results: A total of 3293 commercial RTE refrigerated foods (sushi, n=1882; kimbab, n=975; California rolls, n=436) were collected from Korean grocery stores, department stores and convenience stores between January 2006 and June 2007. Of these, 197 (5·98%) RTE samples were contaminated with coagulase-positive Staph. aureus, that is, 61 (6·26%) kimbab, 110 (5·84%) sushi and 26 (5·96%) California rolls. Multiplex PCR determined the presence of 12 toxigenic genes: sea, seb, sec, sed, see, seg, seh, sei, sej, tst-1, eta and etb. Approximately half (49·75%) of the Staph. aureus isolates had toxigenic properties, and most of the toxigenic isolates possessed genes coding for the simultaneous production of two or more types of toxin. The most frequent toxigenic types found in Korean RTE foods were as follows: seg=sei>sea>tst-1>etb>seh>eta>sec>sej. Conclusions: This study provided a comprehensive analysis of toxigenic S. aureus isolates from Korean RTE foods and their toxigenicity types. This emphasizes the potential risk of various types of toxigenic Staph. aureus in refrigerated RTE food products, which should be better managed to establish safer food chains in global food markets. Significance and Impact of the Study: This result may contribute to an extended database on Staph. aureus food contamination and mitigate the lack of available information on microbiological hazards in Southeast Asian Nations.