Isolation of coagulase-negative staphylococci from the milk and environment of sheep.

Various species of coagulase-negative staphylococci (C-NS) are reported to be common in milk and on the teat skin of domestic ruminants. The commonest C-NS species in mastitic milk of cows varies between reports, with Staphylococcus simulans (Jarp, 1991) in one and Staph. hyicus in another (Watts & Washburn, 1991). The teat skin of heifers may be colonized by Staph. xylosus or Staph. chromogenes, while Staph. chromogenes and Staph. warneri are reported as frequent isolates from teat canals and secretion (Boddie & Nickerson, 1986; White et al. 1989). Staph. haemolyticus was isolated frequently from the nares, the teat skin and the milk of goats (Valle et al. 1991), although others reported Staph. xylosus (Bedidi-Madani et al. 1992) or Staph. epidermidis and Staph. capitis (Kalogridou-Vassiliadou, 1991) as the most predominant C-NS in goats' milk. Staph. simulans has been found experimentally to be pathogenic for the mammary gland of meat ewes (Fthenakis & Jones, 1990), but little is known about the prevalence of this species in ewes' milk collected from cases of naturally occurring subclinical mastitis (SCM). The aim of the present investigation was the identification of the commonest C-NS species in ewes' milk collected from field cases of SCM or predominating in the ewes' environment.