Evaluation of four commercial rapid diagnostic kits for identifying Staphylococcus aureus

Three rapid latex agglutination kits (Aureus Test, Pastorex Staph-Plus, and StaphAurex) and one hemagglutination test kit (SlidexStaph) were compared with the conventional coagulase test for the identification of Staphyloccus aureus. A total of 192 methicillin-resistant S. aureus (MRSA), 75 methicillin-susceptible S. aureus (MSSA) and 86 coagulase-negative staphylococci and Micrococcus spp. were tested. The sensitivities of Aureus Test, Pastorex Staph-Plus, StaphAurex and SlidexStaph were 98.6, 99.4, 90.8 and 97.3%, respectively. Capsular serotypes of 27 strains of MRSA were also determined, in which 15 (55.6%) were capsular serotype 5, 11 (40.7%) were capsular serotype 8, and 1 (3.7%) was nontypeable. All the commercial agglutination kits showed 100% specificity except StaphAurex which had a specificity of only 96.5%. False-positive reactions were found in the strains of S. hominis, S. warneri and unidentified coagulase-negative staphylococci. These results suggest that Aureus Test, Pastorex Staph-Plus, and SlidexStaph are better than StaphAurex for rapid identification of S. aureus.