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

A novel color test for the rapid detection of group A streptococci has been developed. The test, designed to be suitable for use in clinical laboratories as well as by less experienced personnel, incorporates the simplicity of latex tests with a color change to indicate the presence of group A streptococcal antigen. The test, which takes 5 min, was evaluated with 646 throat swabs, with a 15.6% incidence of group A streptococci; for swabs which yielded 10 or more group A streptococcal colonies in cultures, the sensitivity was 96.8%, and the specificity was 99.1%. In addition, the color test was 100% sensitive and specific when used to detect group A streptococcal antigen in beta-hemolytic colonies from culture plates.

Section: Discussionmentioning

confidence: 99%

Novel color test for rapid detection of group A streptococci

Hadfield¹,

Petts²,

Kennedy³

et al. 1987

“…The original Lancefield precipitation method for the serogrouping of beta-hemolytic streptococci has been largely superseded by more rapid and sensitive methods, such as latex agglutination. Latex agglutination has also been used for the rapid detection of bacteria or antigens in blood cultures (12)(13)(14), body fluids (1,5), and swabs taken from various sites of infection (2,3,7,10). Although previous studies indicate that reasonably reliable results can be obtained, the potential for antigenic cross-reactions among different bacteria has not been fully appreciated.…”

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confidence: 99%

Cross-reaction between Streptococcus pneumoniae and group C streptococcal latex reagent

Lee¹,

Wetherall²

1987

The extent of cross-reactivity between Streptococcus pneumoniae and two commercial streptococcal latex grouping reagents was examined. Cross-reactivity with the group C latex reagent was demonstrated in 91% (20 of 22) of blood cultures tested directly and in 97% (73 of 75) of clinical isolates of various serotypes tested after enzymatic extraction. This is important in the clinical laboratory because it may lead to erroneous identification of organisms present in blood cultures.

“…A recent study by Carlson et al (4) described ssA as being a superior tool for GABHS isolation. Overnight anaerobic incubation followed by a second overnight incubation period in an enriched CO2 atmosphere was also described (3).…”

mentioning

confidence: 99%

Effect of medium and cultivation conditions on comparisons between latex agglutination and culture detection of group A streptococci

Graham¹,

Meier²,

Centor³

et al. 1986

In the laboratory diagnosis of pharyngitis, results from latex agglutination tests (LAT) performed directly on throat swabs are often compared with the isolation of group A beta-hemolytic streptococci (GABHS) from simultaneously obtained swabs cultivated on a variety of media under different atmospheric conditions. In this study, results of an LAT, Directigen, were compared with those of two different media: sheep blood agar (SBA) and group A selective strep agar (ssA). Specimens inoculated on SBA were incubated in three different atmospheres: air, 3 to 5% C02, and anaerobically. Those inoculated on ssA were incubated in 3 to 5% CO2 only. Isolation of GABHS was confirmed by coagglutination. The standard for true positivity was the isolation of GABHS from at least one of the simultaneous cultures. Comparisons were made with samples from 693 adult patients. GABHS was isolated on at least one of the three cultures in 143 patients, demonstrating an isolation rate of 20.6%. LAT exhibited a sensitivity of 95.1%. SBA incubated in air, in C02, or anaerobically had sensitivities of 86.2, 85.9, and 93.7%, respectively. The ssA detected 99.3% of the positive specimens. Single SBA culture proved to be inferior to LAT and therefore was a poor standard for measuring LAT performance. Single ssA cultures demonstrated the greatest sensitivity in GABHS detection and therefore could serve as a standard for measuring LAT performance.