National Institute of Animal Health (NIAH)

Topics in Animal Health Research 2002

10. Toxin gene and production in Staphylococcus aureus  from bovine mastitis in various farms in Hokkaido


Staphylococcus aureus is regarded as the most important causal agent of bovine mastitis.  In this study, Enterotoxins (SEs) and TSST-1, which are considered to be superantigens, were examined in 551 strains of S. aureus isolated from bovine mastitis in various parts of Hokkaido.  Of them, 373 strains (67.7%) possessed either the SEs or TSST-1 gene. The SEC gene (sec), seg, sei, and tsst-1 were more often detected at the ratio of 52.3% (288/551), 66.2% (365/551), 66.1% (364/551), and 51.4% (283/551), respectively.  As for the combination of toxin genes, 274 of 373 strains (73.5%) had sec, seg, sei, and tsst-1 simultaneously, and 77 of 373 strains (20.6%) had seg and sei.  Almost all strains (>99%) possessing any toxin genes also produced the respective toxins.  SEC is considered an important pathogenic factor for bovine mastitis, half of the strains tested had sec, together with seg and sei.  In addition to this, approximately 30% of strains without sec possessed both seg and sei.  In the present investigation seg and sei were distributed in S. aureus strains of mastitic origin at a higher rate than sec.  Further study is needed to elucidate the role of SEG and SEI in the pathogenicity of S. aureus for bovine mastitis. (Clinical Epidemiology Section, Department of Epidemiology TEL +81-29-838-7798)