Susceptibility of hemolytic streptococci, other than those of group D, to eleven antibiotics in vitro.

Abstract

There has been confusion in the literature in regard to (1) the relative activity of the available antibiotics against the different varieties of streptococci, and (2) the possible changes that may have occurred in the antibiotic susceptibility of streptococci isolated in different periods and that may have resulted from use of these agents. • -•In some instances, this may have been the result of failure to differentiate among the various species and the serologic groups and types of the streptococci. That species differences, even within the same serologic group, may be important with regard to antibiotic susceptibility was demonstrated in the instance of 3 human pathogenic species of enterococcus (group D streptococci). Even the specific types of hemolytic streptococci of group A are known to be crucial in the occurrence and spread of strains that are resistant to sulfadiazine.------A previous paper from this laboratory dealt with the susceptibility of different varieties of streptococci that were isolated in 1949 and earlier to 7 antibiotics that were then available. Strains of the 3 major divisions (Swift), namely, hemolytic streptococci (mostly of group A), the viridans type of streptococci, and the enterococci, were each studied separately, and they varied in sensitivity to some of the antibiotics. The more recent study of the various species of enterococci was performed with strains that were isolated chiefly in 1954. The present study deals with the antibiotic susceptibility of hemolytic streptococci other than those of group D isolated during 1954 and 1955. It was designed with the following objectives: (1) to determine the relative susceptibility of these recently isolated strains to the currently available, clinically useful