The Biochemical Characters of Human and Animal Strains of Hemolytic Streptococci

The Bacteriology of Bovine Streptococcus Mastitis

In the May 1935 issue of thisJournalthere appeared an article by Gibson and Muir entitled “A study of the streptococci from fifty cases of bovine mastitis”. Since the authors of that article do not appear to have fully appreciated the previous work on the subject, it has become necessary to state the position in the light of research carried out in various countries during the past few years.

85. Non-pathogenic Haemolytic Streptococci Occurring in Milk

A description is given of the characters of certain streptococci which in small numbers are sometimes found in the milk of individual cows. Although the organisms possessed high haemolytic activity, they showed no evidence of pathogenic power, either for the cow's udder or for ordinary small laboratory animals. Not only are they different from the streptococci of bovine mastitis, but they are also to be distinguished from streptococci of theStr. pyogenesgroup which are occasionally found in milk. One of their principal characters is the formation on solid media of minute colonies, consisting of relatively minute cocci, which grow in broth as very short chains.

The fifty-eight strains studied could be divided into two groups on biochemical grounds: (a) those fermenting glucose and lactose with production of small amounts of acid, (b) those which ferment mannite and salicin as well. The former are referred to as “low-acid” strains and the latter asStr. infrequens, as they bear a resemblance to the organism given this name in Holman's classification. Fermentation of sorbite and trehalose occurred with streptococci of both groups.

The two groups could be distinguished fromStr. pyogenesand the ordinary mastitisStreptococcusby direct agglutination. For distinguishing the two groups from each other, agglutinin absorption methods were required. It was then found that the low-acidStreptococcuspossessed two antigens of which one only was represented inStr. infrequens.

COMPARISON OF DIRECT PLATING MEDIA FOR THE ISOLATION AND ENUMERATION OF ENTEROCOCCI IN CERTAIN FROZEN FOODS

A total of 15 agar media were examined for their yield, selectivity, readability, and simplicity of preparation and use. A thallium medium of Barnes was selected as the better of the high yield-fair selectivity type of medium and an azide-citrate medium of Reinbold appeared to be the better of the low yield-high selectivity type of medium. Sodium carbonate (optimal concentration, 0.20%) was found to increase recovery substantially when added to certain media, especially in the presence of 0.05% Tween 80. When these two ingredients were incorporated into a medium modified after Slanetz and Bartley, the resultant medium was superior to other media for the isolation and enumeration of enterococci in certain frozen foods, such as peas and hamburger, by the direct plating method.

A Study of the Streptococci from Fifty cases of Bovine Mastitis

Fifty-one strains recently isolated from cases of bovine mastitis have been studied in their morphological, cultural and biochemical reactions.

Using their colony appearance in blood agar as the first differential criterion we have shown that the strains differ widely from one another and from the α β and γ streptococci usually encountered in human disease.

The heterogeneity of mastitis streptococci was strikingly demonstrated. From the results of a relatively small number of cultural and biochemical tests it could be shown that no two of the fifty-one strains were identical, in every respect.

The findings recorded suggest that great caution must be exercised in ascribing a bovine or human origin to individual strains of streptococci on the results of cultural or biochemical reactions.