Group B streptococcal long-chain reaction.

The streptococcal long-chain reaction was adapted for the measurement of type-specific antibodies to group B beta-hemolytic streptococci (GBBHS). Rabbit antisera incubated with homologous but not heterologous GBBHS produced chains that were 18 to 33 times longer than chains produced by normal rabbit sera. The long chains were easily apparent, in most instances, by scanning the slides. Human sera with mouse protective and opsonic activity against GBBHS serotype Ia produced chains that were always significantly longer than those produced by incubation in nonimmune human sera. Absorption of rabbit or human sera with homologous but not heterologous organisms inhibited the capacity to induce the formation of long chains. The long-chain assay is a simple, rapid, and reproducible test that could constitute a valuable tool for the rapid identification of anti-GBBHS antibodies.