Elucidation of the DNA sequence of Streptococcus uberis adhesion molecule gene (sua) and detection of sua in strains of Streptococcus uberis isolated from geographically diverse locations

Streptococcus uberis is an important environmental pathogen that causes subclinical and clinical mastitis in lactating and nonlactating cows throughout the world. S. uberis adhesion molecule (SUAM) was identified recently by our laboratory and we hypothesize that SUAM is a potential virulence factor involved in the pathogenesis of S. uberis mastitis. The first objective of the present study was to clone and sequence the SUAM gene (sua) from S. uberis UT888. The second objective was to determine the prevalence of sua in strains of S. uberis isolated from geographically diverse locations. The 20 amino acid N-terminal sequence of purified SUAM was utilized to identify a single open reading frame (ORF) in the S. uberis O140J (ATCC BAA-854) genome database. Three sets of primers were identified from this sequence for amplification of sub-fragments and the complete gene encoding SUAM. Restriction fragment analysis of the largest polymerase chain reaction (PCR) product confirmed the desired fragment had been amplified. This 2970 bp PCR fragment was cloned into plasmid pCR-XL-TOPO and sequenced. The S. uberis UT888 sua sequence (NCBI Accession no. DQ232760) was 99% similar to the S. uberis O140J database sequence. The three pairs of PCR primers were used in a subsequent experiment to identify sua in 12 strains of S. uberis isolated in milk from dairy cows with mastitis in Tennessee (n = 6), Colorado (n = 1), Washington (n = 1), New Zealand (n = 1) and from the American Type Culture Collection (n = 3). Primer pairs yielded the expected 2970, 2639 and 2362 bp PCR fragments in all strains evaluated. In conclusion, we cloned and sequenced sua, which codes for the first described S. uberis adhesin, SUAM. sua was detected in all strains of S. uberis evaluated suggesting that it is conserved.