Evaluation of the API 20 STREP system for species identification of "viridans" streptococci isolated from bacteremia

Species identifications of 71 strains of viridans streptococci isolated from blood and 4 reference strains were made by the API 20 STREP system (API system S. A., Montalieu-Vercien, France) and the conventional method. There are high levels of agreement between results obtained with the both methods for determining acidification from carbohydrate except inulin. The API 20 STREP system correctly identified 74.7% of the viridans streptococci with 9.3% low descrimination, 12% incorrect and 4% unidentified. All strains of S. mitis, S. mutans, S. salivarius and S. anginosus-constellatus were correctly identified. The correct identification rates for S. sanguis I, S. sanguis II and S. MG-intermedius were 88.9%, 68% and 61% respectively. The difference of inulin reaction and the taxonomy discrepancy may be the cause of different identification. The study indicates that the API 20 STREP system has a good potentiality for species identification of viridans streptococci at present time, however, further refinement in needed.