Comparative evaluation of Vitek Gram-positive identification system and API Rapid Strep system for identification of Streptococcu species of bovine origin

The Vitek Gram-positive identification system (GPI, Vitek Systems, Inc., Hazelwood, MO) and the API Rapid Strep system (Analytab Products, Plainview, NY) were evaluated for species identification of streptococci isolated from bovine mammary glands and compared to conventional biochemical methods. A total of 144 strains including Streptococcus uberis (60), S. dysgalactine (32), S. agalactiae (15), S. bovis (15), Enterococcus faecium (10) and Ent. faecalis (12) were evaluated. All references strains were identified correctly by both systems. Vitek GPI card system identified 94.4% of strains, including 95% od S. uberis, 93.8% of S. dysgalactiae, 93.3% of S. agalactiae and S. bovis II, 90% of Ent. faecium and 100% of Ent. faecalis. Majority of strains were identified with a 90-99% level of confidence, with an average of 8 h needed for identification. The API Rapis Strep system identified 96.5% of strains correctly, incluidng 95% of S. uberis, 96.6% of S. dysgalactiae, 93.3% of S. agalactiae, and 100% of S. bovis II, Ent. faecium, and Ent. faecalis. Majority pf strains were identified with excellent level of identification. With the exception of S. uberis, most strains were identified at 4 h of incubation.