REPORT OF CASES OF AND TAXONOMIC CONSIDERATIONS FOR LARGE-COLONY-FORMING LANCEFIELD GROUP-C STREPTOCOCCAL BACTEREMIA

Traditionally, group C streptococci include four species: Streptococcu s equisimilis, S. zooepidemicus, S. equi, and S. dysgalactiae, the fir st three of which are group C beta-hemolytic streptococci (GCBHS), How ever, many of the beta-hemolytic streptococci carrying Lancefield grou p C antigen isolated from clinical specimens are S. mulleri, These org anisms can be differentiated by colony size, We retrospectively collec ted data concerning large-colony-forming GCBHS bacteremia that occurre d during a period of 8 years at the Massachusetts General Hospital. A total of 222 cases of beta-hemolytic streptococcal bacteremia were ide ntified; data on the Lancefield grouping were available in 192 cases: 45 cases (23.6%) were group A, 96 cases (50%) were group B, 7 cases (3 .6%) were group C (large colony forming), and 44 cases (22.9) were gro up G. The medical records for cases of large-colony-forming GCBHS bact eremia were reviewed, In one case, the isolate was thought to be a con taminant; the other six cases are reported (five males and one female; mean age, 55 years). All patients had severe underlying conditions, a nd none had a history of exposure to animals, The clinical syndromes i ncluded two cases of cellulitis and one case each of endocarditis, myo cardial infarction complicated by infection, pneumonia, and myofasciit is, The diagnoses for two patients with endovascular infections were d elayed, Three of the six patients had fatal outcomes, and other two, a fter prolonged hospitalization, were transferred to a long-term rehabi litation center, We concluded that the severe outcomes reflect delay i n diagnosis and treatment as well as the severity of the underlying di seases, The taxonomy of GCBHS is discussed, More reports differentiati ng large- and small-colony-forming GCBHS are needed.