Use of an inhibitor typing scheme to study the epidemiology of Streptococcus uberis mastitis

An inhibitor typing scheme, based on the production of and sensitivity to bacteriocin-like inhibitor substances was used to identify strains of Streptococcus uberis obtained from skin swabs and milk samples of dairy cows. Thirty-nine isolates from one herd were compared, with one isolate examined per site for any sampling day. Eighteen different inhibitor profiles were observed from these isolates. When several isolates were obtained from various skin sites on a cow on the same day, the inhibitor profiles were all different. In three cases, Str. uberis was simultaneously isolated from milk sample and teat surface of the same quarter, but similar inhibitor profiles were only observed for one pair of isolates. Furthermore, when several isolates were obtained by repeated swabbing of a single skin site on a cow on the same day, differences in the inhibitor profiles were again seen. It is likely that numerous strains of Str. uberis are capable of producing clinical mastitis since a comparison of ten isolates obtained from cases of clinical mastitis revealed eight different inhibitor profiles. Monthly sampling (April-November) of eleven cows revealed that Str. uberis could be isolated from the skin of the abdominal wall, medial thigh, udder and teats, but was not isolated from the rectum of any of the cows. Str. uberis was more frequently isolated from the skin and milk samples during the winter when the cows had been dried off, than during the spring and autumn.