Genetic and serologic evaluation of capsule production by bovine mammary isolates of Staphylococcus aureus and other Staphylococcus spp. from Europe and the United States

Bovine mastitis caused by Staphylococcus aureus is responsible for major ec onomic losses to the dairy industry, and more-effective therapeutic or prev entive approaches are sorely needed, The predominance of staphylococcal cap sular polysaccharide types 5 and 8 among human isolates from many sources i s well documented, but there seems to be a greater variation in the distrib ution of capsular serotypes among isolates from cows. A total of 636 isolat es of S, aureus from cases of bovine mastitis in Sweden, Denmark Finland, I celand, ireland, and the United States were investigated for production of capsular polysaccharide types 5 and 8, Approximately half of all the Europe an isolates tested were of serotype 8, although variation among countries a nd among isolates of clinical and subclinical origin was observed. Sweden h ad the highest frequency (87%) of serotypeable isolates, and Finland had th e lowest (48%). Capsule types 5 and 8 accounted for only 42% of the U.S. is olates tested. A few isolates showed weak reactivity with CP5 antiserum in a colony blot assay, and an enzyme-linked immunosorbent assay inhibition me thod confirmed that the levels of capsule produced by these strains were <1 0% of those produced by control strains. fifty isolates that failed to reac t with capsular antisera all possessed the genes for production of capsular polysaccharide type 5 or 8, These results underscore the variability in ca psule production by bovine isolates of S. aureus from different geographic regions. This information is important for the rational design of a capsule -based vaccine to prevent S, aureus bovine mastitis.