Evaluation of Detect-A-Strep and the Culturette Ten-Minute Strep ID kits for detection of group A streptococcal antigen in oropharyngeal swabs from children.

The Detect-A-Strep kit (DAS) (Antibodies Inc.) and the Culturette Brand 10-Minute Group A Strep ID kit (CBTMSI) (Marion Scientific) were compared with a sensitive culture method for detection of group A streptococci in oropharyngeal swabs from children. Specimens from 953 children ranging in age from 4 months to 18 years were inoculated to selective blood agar plates containing sulfamethoxazole-trimethoprim. Culture plates were incubated anaerobically for the first overnight period and aerobically in the presence of 10% CO2 for the second overnight period. The same specimens were tested within 24 h by DAS (phase 1) or CBTMSI (phase 2). One hundred thirty-five of 538 specimens (25.1%) tested by DAS and 150 of 415 specimens (36.1%) tested by CBTMSI were culture positive. DAS detected 87 of 135 (64.4%) and CBTMSI detected 93 of 150 (62.0%) culture-positive specimens. The specificities of DAS and CBTMSI were 96.5 and 99.6%, respectively. The predictive values of positive and negative results were 86.1 and 89.0% for DAS and 98.9 and 82.2% for CBTMSI. Because a reliable distinction between infected patients and carrier state patients cannot be made, we conclude that neither DAS nor CBTMSI is sufficiently sensitive to replace our culture method.

Comparison of the API Staph-Ident and DMS Staph-Trac systems with conventional methods used for the identification of coagulase-negative staphylococci.

Two commercial kit systems, the API Staph-Ident system (Analytab Products, Inc., Plainview, N.Y.) and the DMS Staph-Trac system (DMS Laboratories, Inc., Flemington, N.J.), were compared with conventional methods for the identification of nine species of coagulase-negative staphylococci. The API Staph-Ident system, a biochemical and chromogenic substrate micromethod, correctly identified 95 of 120 (79.2%) clinical isolates of coagulase-negative staphylococci after 5 h of incubation. The DMS Staph-Trac system, a miniaturized biochemical test system which requires a 24-h incubation period, correctly identified 106 (88.3%) of the same isolates. Both commercial systems were similar in cost and amount of technologist time required to inoculate and read each system. The clinical value of routine species identification of coagulase-negative staphylococci has not yet been established. The decision by clinical laboratories of whether to adopt this practice will be greatly facilitated by the availability of commercial kit systems which are both rapid and accurate.