Group B streptococcus-comparison of Streptococcus agalactiae isolated from humans and cows in the Republic of South Africa.

The serological and biochemical characteristics of 100 strains of Streptococcus agalactiae isolated from quarter mild of dairy cows and of 107 strains cultured from various sites of human patients, were determined and compared. All the isolates were CAMP-phenomenon and Na-hippurate positive, aesulin negative, fell into Lancefield's Group B and could be placed into one of the 6 recognised serotypes. No human isolates fell into type R but for the rest all the other types were represented in the series of bovine and human cultures. In order of frequency, the human isolates were of type III, II, Ib, X and Ia and the bovine of type II, X, III, Ia, Ib and R. Of the human and bovine cultures respectively, 34 and 96% altered litmus milk, 30 and 100% were sensitive to bacitracin, 32 and 4% were pathogenic to mice, 82 and 93% reduced the ultimate pH of glucose broth to 4,2-4,8, 36 and 100% fermented lactose, 93 and 99% salicin and 94 and 79% trehalose. Concerning the combination of lactose/salicin fermentation, 35 and 95% of bovine and human isolates were , 0 and 5% were , 59 and 0% were -/=nd 7 and 0% were -/-. Data are summarised in 5 tables and discussed against the background of reports from other countries. It appears that a proportion of the human infections concern organisms likely to have been derived from bovine sources, either directly or indirectly. Definite classification of South African GBS into either human or animal strains does not seem possible. It is concluded that it would be more correct to refer to the source of an isolate instead of inferring that because the organism was primarily cultured from, say human resources, it is necessarily a human "strain'.