The association between leukocidin M and F’ expression by Staphylococcus aureus strains and the clinical severity of ruminant mastitis

Abstract

Staphylococcus aureus is an important causative agent of ruminant mastitis. The bacterium has several ways of immune evasion, of which the production of bicomponent leukocidins is one. It is suggested that LukMF’, a leukocidin almost exclusively produced by ruminant S. aureus strains, is the most important leukocidin in vitro. To elucidate the importance of this toxin in ruminant mastitis, milksamples were taken from sheep and cows to determine the prevalence of the LukMF’ genes, study the in vivo and in vitro production of the toxin and relate the production of LukM to the somatic cell count (SCC) and clinical features of the concerning animals. A high prevalence of LukMF’ was found in both the sheep- and the cow isolates, but presence of the genes was not associated with the severity of mastitis. LukM production in vitro couldn’t be associated with the severity of mastitis but an association was found between the presence of LukM in vivo and the severity of mastitis.