Clinical significance of Lancefield groups L-T streptococci isolated from blood and cerebrospinal fluid.

The aim of a study of all groups L-T streptococci isolated at the Massachusetts General Hospital during a 10-year period (1964-1974) was to ascertain the clinical significance of the less frequently occurring serological groups of streptococci. No organisms of groups P,R,S, or T were found during this time. The case records of 109 clinical isolates of alpha-reacting streptococci of Lancefield groups L,M,N, and O from blood and cerebrospinal fluid cultures were reviewed. There were six cases of endocarditis and one case of infected sternotomy uound with septicemia due to these streptococci. The two cases of endocarditis due to group O streptococci represent the first cases described with endocarditis caused by this group of organisms. Virtually all of the isolates of groups L,M,N, and O streptococci were susceptible to penicillin. Seventy-four percent of the isolates were judged not responsible for clinical disease. The importance of avoiding inappropriate therapy makes it necessary to realize that these organisms are potential "contaminants" of cultures of blood and cerebrospinal fluid.