Latex Agglutination Test Identifies Bacterial Groups

The kit is designed to improve workflow efficiencies since the nitrous acid extraction instantaneously extracts the cell antigens and the test does not require rehydration or incubation.

Beta-hemolytic streptococci may be identified rapidly and accurately according to the presence of specific cell wall antigens in a process called Lancefield Grouping. This process is most conveniently carried out using latex agglutination. To prepare the antigens for a latex agglutination reaction, an enzyme-mediated or nitrous acid extraction method may be used. Commercially available nitrous acid extraction kits are not traditionally capable of detecting group D antigen.

The PathoDxtra Strep Grouping Kit a latex agglutination kit from Thermo Fisher Scientific (Basingstoke, UK), detects groups A, B, C, D, F, and G antigen using a nitrous acid extraction method. The company report that a test panel of 131 beta-hemolytic streptococci have been assayed, including: Lancefield 21 group A, 27 B, 20 C , 23 D, 20 F, and 20 G. Thirty non-Lancefield group isolates were also tested, including: Streptococcus pneumoniae, S. viridans, Staphylococcus aureus, and Listeria monocytogenes. The kit was compared with other commercial kits.

All kits showed 100% accuracy in identifying all Lancefield group A and group C isolates. For the remaining isolates, PathoDxtra Strep Grouping Kit performed better than or comparable to all other products examined. The overall performance of kits that included a group D latex showed that PathoDxtra Strep Grouping Kit correctly identified 150/161 (93.2%) of the isolates tested. PathoDxtra Strep Grouping Kit agglutination reactions were consistently strong and exhibited a fast agglutination reaction for all Lancefield groups, providing results within 20 seconds.

Julie Elston, global product manager, immunodiagnostics, at Thermo Fisher said, "Acid extraction kits offered speed but did not detect group D strep reliably, while enzyme kits detected all groups but required rehydration and incubation steps, adding significant time to testing procedures. With PathoDxtra there is no compromise, this kits gives instantaneous extraction and detects all clinically significant streps reliably, including group D. It really couldn’t be simpler.”

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