IDENTIFICATION OF STREPTOCOCCUS SPECIES BY RANDOMLY AMPLIFIED POLYMORPHIC DEOXYRIBONUCLEIC-ACID FINGERPRINTING

Identification of Streptococcus species isolated from bovine milk by r andomly amplified polymorphic DNA fingerprinting was evaluated. Bacter ial DNA templates were prepared using a standardized method for random ly amplified polymorphic DNA amplification and previously evaluated ar bitrary primers. Amplified DNA fragments were visualized by agarose ge l electrophoresis and were analyzed by densitometry. Unidentified stre ptococci(n = 163) that were isolated from mammary secretions of dairy cows we-re evaluated. The DNA fingerprint patterns of unidentified bac teria were compared using a computerized database that contained DNA f ingerprint patterns of test strains. Comparison with the API 20 Strep identification system (bioMerieux Vitek, Inc., Hazelwood, MO) and conv entional biochemical tests showed that about 91% of isolates (148 of 1 63) were identified correctly by DNA fingerprinting. The sensitivity o f the DNA fingerprinting technique was 90%, and the specificity was 92 %. However, the DNA fingerprinting technique only identified 4 of the 11 species included in the study. Three of the 4 species, Streptococcu s uberis, Streptococcus agalactiae, and Streptococcus dysgalactiae, re present the streptococci isolated most frequently from cows with masti tis. The other Streptococcus and Enterococcus species that were not id entified by the DNA fingerprinting system are less frequently isolated as causative agents of mastitis. Expanding the DNA fingerprint databa se would likely increase the sensitivity and specificity of this techn ique.