Speciation of clinical isolates of group C haemolytic streptococci harvested in North Yorkshire, England

All Lancefield group C haemolytic streptococci isolated from routine clinical specimens over four years were collected to determine the species composition. Of a total of 102 viable isolates studied, 71 (70%) were large colony-forming Streptococcus dysgalactiae equisimilis; they were from patients of all ages (predominantly the 11-20 year age group), mainly (72%) from the throat or wound swabs but some from genital, blood and other sites. Thirty (29%) of the isolates were of the small colony-forming 'Streptococcus milleri' group (Streptococcus anginosus = 21, Streptococcus constellatus = 9) from patients in the age group of 10-70 years (predominantly 21-30 years); two-thirds of these isolates were from the throat, with others from genital, wound and other sites. Comparison of results with studies of earlier collections of group C streptococci showed broad similarity, although other researchers have often found a higher proportion of S. milleri strains. The continuing low incidence of human infection with Streptococcus zooepidemicus here is confirmed.