Exoprotein and slime production by coagulase-negative staphylococci isolated from goats' milk

Abstract

Milk from mastitis-free goats from French herds was examined for the presence of coagulase-negative staphylococci (CNS), and 165 positive isolates were evaluated for their capacity to produce exoproteins. Most isolates were identified as Staphylococcus caprae (N = 91) or S. xylosus (N = 36), but members of at least nine other species were present. Overall, some 57% of isolates produced toxins with phenotypic properties of alpha-hemolysin, and 75% produced toxins resembling S. aureus beta and/or delta-hemolysins. Thermostable desoxyribonuclease (TNAse) was secreted by 29% of isolates and thermolabile DNAse by 66%. Slime was produced by 42% of our cultures and, although none of them showed activity to insoluble elastase, over 70% lysed the soluble substrate. No clinical consequences were observed to correlate with exoprotein production, which proved to be inconstant within individual CNS species.