Distribution of newly described enterotoxin-like genes in Staphylococcus aureus isolated from ready-to-eat foods in Korea

Abstract

To investigate the distribution of staphylococcal enterotoxin-like (SEl) genes in Staphylococcus aureus from food, a total of 154 S. aureus isolates from ready-to-eat (RTE) foods in Korea were analyzed by mutiplex PCR for the detection of the following 9 staphylococcal enterotoxin-like genes; sek, sel, sem, sen, seo, sep, seq, ser, and seu. Seventy-nine isolates (51.3%) were found to have at least one of SEl genes. The major SEl genes were sek, sem, sen, and seq. Other SEl genes found in the isolates were seo (21 isolates, 13.6%), seu (12 isolates, 7.8%), sep (8 isolates, 5.2%), sel (7 isolates, 4.5%), and ser (2 isolates, 1.3%). Most (95%) of the isolates with staphylococcal enterotoxin (SE) genes were also carried SEl genes. The genes seg, sei, sem, and sen were all detected in the same isolates. Ninety-seven % of isolates with seg+sei+sem+sen also contained seo or seu. Ninety-four % of isolates with sea+seh were found to coexist with sek+seq. The toxic shock syndrome toxin gene, tst-1, was found in all isolates with egc-2, including seg, sei, sem, sen, and seu. The coexistence of SE and SEl genes in S. aureus isolates from RTE foods can be explained by the mobile genetic elements. Because of the mobile genetic element, SE and SEl genes of S. aureus in foods may be transferable to nontoxigenic S. aureus and other food pathogens. Additional studies must be conducted to prevent spread of pathogenic genes such as enterotoxin gene.