Pattern of enterotoxin genes seg, seh, sei and sej positive Staphylococcus aureus isolated from bovine mastitis.

PCR detection of the genes encoding the newly described staphylococcal enterotoxins (SE) SEG, SEH, SEI and SEJ was carried out for 104 randomly selected Staphylococcus aureus field strains isolated from cases of bovine mastitis. Sixty-one (58.7%) isolates were positive for one or more of these novel enterotoxin genes. Thirty-six field strains were classified as carrier of seg, 22 of sei gene and 23 were positive for sej gene. None of the 104 investigated ruminant S. aureus strains carried the seh gene. Thirty-seven of these S. aureus strains showed a combination of genes encoding enterotoxin types SEA to SEE or toxic shock syndrome toxin 1 (TSST 1). Thirteen cultures harboured only one, 28 two, 12 three and 8 four enterotoxin genes. Among the 61 S. aureus field strains 14 (23.0%) were positive for the genes encoding SEJ and SED and 10 (16.4%) isolates for those encoding SEG and SEI. Isolates harbouring the sed/sej genes were further characterized by macrorestriction analysis and pulsed-field-gelelectrophoresis (Pfge). Macrorestriction analysis revealed six patterns. Nine of these14 S. aureus isolates (64.3%) exhibited two patterns with a high degree of relationship (>80%).