Rapid detection of group C streptococci from animals by latex agglutination.

A group C latex agglutination reagent, included as the negative control in the PathoDx Strep A latex agglutination test (Diagnostic Products Corp., Los Angeles, Calif), was compared with culture for rapid detection of group C streptococci (Streptococcus equi, S. equisimilis, S. zooepidemicus, and S. dysgalactiae) from swabs of veterinary specimens. The overall sensitivity of the latex test was 78%, and specificity was 97.6%. Only 25% of S. dysgalactiae isolates were detected, thereby accounting for the relatively low sensitivity. Ninety-three percent of the group C streptococci other than S. dysgalactiae were isolated from horses. When the latex test was evaluated for detection of group C streptococci other than S. dysgalactiae from horses, the sensitivity and specificity were 95.3 and 100%, respectively. We found the group C latex agglutination test to be a rapid and accurate method for the detection of the major pathogenic group C streptococci from swabs of equine specimens.