Identification of streptococci isolated from various sources by determination of cfb gene and other CAMP-factor genes.

In the present study, the CAMP-factor (cfb) gene of streptococci of serological group B (Streptococcus agalactiae) and the CAMP-factor (cfu) gene of S. uberis could be amplified by polymerase chain reaction. A cfb specific amplicon could be observed for all 128 phenotypically CAMP-positive S. agalactiae, for the phenotypically CAMP-negative S. agalactiae strain 74-360, and for 2 S. difficile reference strains. A cfu specific amplicon could be observed for all 7 phenotypically CAMP-positive S. uberis. Four S. agalactiae strains isolated from 4 cows with mastitis appeared to be phenotypically CAMP-negative and negative in the cfb gene PCR. The CAMP-positive and CAMP-negative isolates, including both S. difficile, could be identified as S. agalactiae by amplification of a S. agalactiae specific part of the V2 region of the 16S rRNA and a species-specific part of the 16S-23S rRNA intergenic spacer region. Amplification of an internal fragment of the cfb gene with a reduced annealing temperature yielded positive reactions not only for CAMP-positive S. agalactiae, but also for phenotypically CAMP-positive S. pyogenes (n = 4), S. canis (n = 28), and S. uberis (n = 7), indicating a close relation of the CAMP genes of these 4 species. The relation could be further demonstrated by sequencing the internal fragment of the CAMP-factor (cfg) gene of S. canis and comparing the sequence with those of S. agalactiae, S. pyogenes, and S. uberis.