Early detection of streptococci in swabs by latex agglutination before culture

Abstract

A commercial streptococcal grouping system was used to demonstrate streptococcal antigen in swabs before culture. The method detected 81% of the streptococci of groups A, B, C, and G subsequently isolated in culture. The method offers a sensitive and specific method for the early detection of beta-hemolytic streptococci.

Latex agglutination testing directly from throat swabs for rapid detection of beta-hemolytic streptococci from Lancefield serogroup C

“…There are several possible explanations for the few positive rapid tests which were not confirmed by culture. Antigenic cross-reactions between group C BHS and S. pneumoniae and Klebsiella pneumoniae have been reported by using latex agglutination methods with blood culture and skin swab specimens (9,12,17). False-positive results of the trivalent color test for group C organisms have also been reported for individuals with blood group A (13).…”

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

“…The original Lancefield precipitation method for the serogrouping of beta-hemolytic streptococci has been largely superseded by more rapid and sensitive methods, such as latex agglutination.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.…”

“…The results of this study further highlight the problem of mistaking S. pneumoniae for group C streptococci when blood cultures growing streptococci are tested directly by latex agglutination. This may not be a significant problem, provided that these blood cultures are also tested with a latex reagent directed against S. pneumoniae and undergo a rapid bile solubility test (8,10).…”

Enzyme release of antigen from Streptococcus faecalis and Listeria monocytogenes cross-reactive with Lancefield group G typing reagents

“…Commercially produced kits such as Streptex (Burroughs Wellcome Co., Research Triangle Park, N.C.) and Phadebact Streptococcus Test (Pharmacia Diagnostics, Piscataway, N.J.) were intially designed to group streptococci that produce beta-hemolysis on blood-containing agar. The kits have been evaluated for the rapid detection of antigen in blood cultures (18,22,23), enrichment broths from vaginal (8,9,11,14,20) and throat (19) specimens, and directly from throat secretions (4) and swabs (12,16). In general, these applications have been shown to provide accurate and reliable information.…”