Comparative grouping of mastitis Streptococci by means of co-agglutination and precipitation

Two hundred bovine mastitis streptococcal strains belonging to groups B, C, E, G and L were tested comparatively by means of the co-agglutination and precipitation technique. Identical results were obtained with the two tests in 191, or 95.5 %, of the strains. Six strains, which could not be grouped by co-agglutination, proved to belong to group B when grouped by precipitation. On the other hand, one strain which proved to belong to group G and two strains to group L when grouped by co-agglutination, could not be grouped by precipitation. Some cross-reactivity was observed between groups A and C, B and G, B and L. Only a few L strains showed marked cross-reactivity which was not easily distinguished from specific reactions. However, the cross-reactivity ought to be eliminated by dilution or adsorption. Using the precipitation test as a supplementary method, the easy and rapid co-agglutination test was found to be a suitable procedure for routine grouping of mastitis streptococci.