Biochemical characteristics of typical and atypical "Staphylococcus aureus" in mastitic milk and environmental samples of brazilian dairy farms

RESUMO

This study results on the biochemical characteristics of 274 "Staphylococcus aureus" strains isolated from mastitic milk, hands of milkmen and milking machines. Features included colony morphology on Baird Parker agar (BPA), catalase, coagulase, and thermonuclease tests. API-Staph (BioMérieux, France) was used as reference identification system. 39.4(per cent) of the colonies on BPA identified as "S. aureus" were atypical. They were more frequent in milk samples (94.4(per cent)). All "S. aureus" strains were coagulase positive but intensify of the test varied according to the source: enviromental strains were 3+ or 4+, while 17.1(per cent) of strains isolated from milk presented only 1+ or 2+ results. The majority of atypical "S. aureus" strains presented a 4+ coagulase result. 2.2(per cent) of "S. aureus" strains were thermonuclease negative. Sixteen thermonuclease positive and coagulase positive strains were identified as "S. hyicus"