1. 5 per cent sheep blood agar is a selective medium for beta hemolytic streptococci in throat cultures since sheep blood inhibits the growth of bacillus X (H. hemolyticus) and B. parainfluenzae hemolyticus. The growth of H. influenzae is also inhibited by sheep blood. 2. The inhibitory action of sheep blood resides in the erythrocytes and is thermolabile. Disruption of the cell by laking has n...

Two methods of typing group A hemolytic streptococci have been described: slide agglutination and anti-M precipitin tests. The first, developed by Griffith (1), is more extensively used. I t has the distinct advantages of requiring small amounts of serum and culture, and of a quick reaction time when all conditions are favorable. I t has certain disadvantages: The granular growth of some strain...

Since the division of the Streptococcus genus into enterococci, lactococci, and streptococci in 1984, many changes in the nomenclature and taxonomy of the Streptococcus genus have taken place. The application of genetic comparisons has improved the proper classification of the different species. The Lancefield system of serogrouping the streptococci by the expression of beta-hemolysis on blood ...

Actinobacillus actinomycetemcomitans is the etiologic agent of localized aggressive periodontitis, a rapidly progressing oral disease that occurs in adolescents. A. actinomycetemcomitans can also cause systemic disease, including infective endocarditis. In early work on A. actinomycetemcomitans workers concluded that this bacterium is not beta-hemolytic. More recent reports have suggested that ...

staphylococci isolated from 98 mastitic cow’s milk samples were analyzed for the production of alpha,beta and delta-hemolysin on sheep, bovine and horse red blood cells and in vitro susceptibility to several antimicrobial agents. out of a total of 18 isolated strains, 100% demonstrated hemolytic activity either alone or in combined forms. among 8 isolates of s. aureus 3 isolates produced α/β an...