LANCEFIELD GROUPING AND SMELL OF CARAMEL FOR PRESUMPTIVE IDENTIFICATION AND ASSESSMENT OF PATHOGENICITY IN THE STREPTOCOCCUS-MILLERI GROUP

Aims-To evaluate Lancefield grouping and caramel smell for presumptive identification of the Streptococcus milleri group, and to find whethe r Lancefield group, species, or protein profile correlated with virule nce or infection site. Methods-Prospective studies were made of 100 co nsecutive streptococcal isolates in blood cultures or pus from 100 pat ients in whom the severity of infection was categorised as serious, mo derate, or not significant. The usefulness of Lancefield group and the caramel smell for presumptive identification was examined, and the re lation of the S milleri species, Lancefield group, and SDS-PAGE protei n analysis to severity of infection and infection site was investigate d. Lower respiratory tract and genital tract specimens, strict anaerob es, group D streptococci, and strains identified as Streptococcus pneu moniae, Streptococcus pyogenes, or Streptococcus agalactiae were exclu ded. Results-Most streptococci occurring in pure or significant growth density were S milleri group (87/100; 87%, 95% confidence interval 0. 81-0.93). Of these, 89.7% (78/87; 0.84-0.96) were associated with infe ction. Lancefield group F antigen predominated (41/87; 47.1%, 0.38-0.5 6). Lancefield group F alone or accompanied by the caramel smell had a specificity of 100%, but a sensitivity of only 47.3% for group F alon e, and 19.5% for group F accompanied by the caramel smell. There was n o significant association between species, Lancefield group, and sever ity of infection, site of infection, or pathogenicity. SDS-PAGE analys is failed to discriminate between strains. Conclusions-Neither species nor Lancefield antigen was related to the site of infection. The pres ence of Lancefield group F antigen alone or accompanied by a caramel s mell was a useful indicator for the S milleri group when present, but was too insensitive to use as a screening test. Most streptococci occu rring in pure culture or in significant growth density were of clinica l importance. Such organisms should be identified to species level to detect the S milleri group.