title: Comparison of commercial slide agglutination kits with a tube coagulase test for the rapid identification of Staphylococcus aureus from blood culture.
abstract: Eighty clinical specimens of BACTEC 9240 blood culture vials, culture positive for staphylococci (38 Staphylococcus aureus and 42 coagulase negative staphylococci), were tested directly for the presence of clumping factor/protein A and free coagulase. Seven commercial slide agglutination kits were compared with a direct-tube coagulase (DTC) method. All tests were performed on blood culture pellets. Sensitivity, specificity, and negative and positive predictive values for the seven commercial kits were extremely variable, whereas a two-hour DTC test was highly predictive of S aureus. There was no significant difference between a two-, six- or 24-hour DTC test. Three (8%) S aureus isolates remained DTC negative even after 24 hours' incubation. Staphylococcal slide agglutination kits should not be used directly on blood culture broths. In contrast, a two-hour DTC test is a useful, rapid screening test for S aureus bacteraemia, provided isolates from DTC negative blood culture broths are re-tested using standard laboratory techniques.
authors.affiliation: Department of Medical Microbiology, District General Hospital, East Sussex.
authors.forename: R P
authors.initials: RP
authors.lastname: Cooke
authors.forename: C T
authors.initials: CT
authors.lastname: Jenkins
mesh_terms: D000372:Agglutination Tests; D001431:Bacteriological Techniques / Q000592:standards*; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000097:blood* / Q000175:diagnosis; D013211:Staphylococcus aureus / Q000302:isolation & purification*
chemical_list: D011933:Reagent Kits, Diagnostic