Evaluation of a rapid latex agglutination test for identification of group D streptococci

The SeroSTAT latex agglutination test (Scott Laboratories, Inc., Fiskesville, R.I.) for identification of group D streptococci was compared with bile-esculin agar and Lancefield grouping by using 110 clinical isolates of group D streptococci (S. faecalis, 74; S. bovis, 24; S. durans, 3; S. faecium, 9) and 65 viridans streptococci (S. anginosus-constellatus, 2; Streptococcus MG, 15; S. sanguis II, 14; S. mitis, 7; S. mutans, 5; S. salivarius, 8; S. sanguis I, 8; S. acidominimus, 1; S. morbillorum, 2; S. pneumoniae, 3). All strains of group D streptococci were bile-esculin positive. SeroSTAT reactions were falsely positive with 2 strains of S. sanguisII and 1 strain of Streptococcus MG (4.6% of all viridans streptococci tested) and falsely negative with 10 S. bovis, 8 S. faecalis, 1 S. durans, and 6 S. faecium strains (22.7% of all group D streptococci tested). When considered with colonial morphology and hemolytic reaction, SeroSTAT is a rapid (60-s) and useful test for recognition of group D streptococci.