High incidence of group C streptococci isolated from throat swabs

Group C streptococci in human infection: a study of 308 isolates with clinical correlations

A collection of 308 clinical isolates of beta-haemolytic Lancefield group C streptococci was assembled from laboratories in England, Nigeria and New Zealand. Of these, 276 isolates were Streptococcus equisimilis, 23 S. milleri and nine S. zooepidemicus. Isolates of S. equisimilis in the African collection, though few, gave higher rates of lactose and raffinose fermentation, aesculin hydrolysis and positive alpha-galactosidase reactions than those from elsewhere. Erythromycin resistance was found in 1.9% of the English isolates of S. equisimilis. Strains from superficial infections accounted for 88% of the collection and were most commonly isolated from the upper respiratory tract, skin or wounds. Amongst the 36 patients yielding isolates from deep sites S. equisimilis was found in septicaemia, cellulitis, abscess, peritonitis, septic arthritis, pneumonia, mycotic aneurysm and acute epiglottitis, S. milleri was found in abdominal abscesses, peritonitis, pleural empyema and osteomyelitis and S. zooepidemicus was found in septicaemia, pneumonia, meningitis and septic arthritis. Within the collection an unselected general catchment of 214 isolates of group C streptococci from the laboratories in Yorkshire showed the following species: from 199 superficial infections 94% S. equisimilis, 5% S. milleri and 1% S. zooepidemicus and 15 patients with deeper, more aggressive infections 67, 27 and 6.7% of these species respectively.

Direct detection of groups A, C and G streptococci in clinical specimens by a trivalent colour test

A simple trivalent colour test, developed for the rapid detection and identification of streptococci belonging to Lancefield groups A, C and G, was evaluated for sensitivity and specificity with cultures and when directly used with wound and throat swabs. In tests performed on cultures, all of 94 group A, 78 group C and 94 group G cultures were correctly identified. In direct tests on wound swabs, 49 of 52 group A, 17 of 19 group C and 48 of 51 group G streptococci were detected and correctly identified; no false positives were observed. With throat swabs from pharyngitis patients 34 of 36 group A, 3 of 6 group C and 5 of 8 group G streptococci gave positive results. Almost 10% of these swabs gave false positive reactions with the group C component of the test system. Samples taken from uninfected individuals indicated that the false positives were probably associated with blood group A. The test system gives rapid and reliable results with streptococcal cultures, but when directly applied to clinical samples the results must be interpreted with caution, particularly if the patient's blood group is not known.

Separation of lymphocytes from peripheral blood: a revisitation

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