We found that the skc gene was harboured by 65.3% of the strains. To our knowledge, only one study has investigated the skc
gene in S. uberis (Johnsen et al., 1999); nine of 10 investigated strains contained skc genes with similar structures and properties. Evidence of pauB was not found in S. uberis herein. Only one report describes the presence of the pauB gene in one S. uberis strain isolated from a clinical case of bovine mastitis (Ward & Leigh, 2002). Our results showed that 61.5% Bleomycin of the strains harboured the pauA gene. In contrast, Ward & Leigh (2004) reported a very high prevalence of pauA alleles in field isolates collected from various European locations, which supported the Trichostatin A ic50 observation that plasminogen activators are likely to confer an advantage with respect to colonization and growth. However, Ward et al. (2003) reported that expression of PauA is not essential for infection of the mammary gland, as indicated by the isolation of pauA-negative isolates from mastitic cows and by experimental studies. It is unclear why the pauA gene was found at low frequency in this work. According to the identification scheme used, 78 strains could be
identified as representing S. uberis. Although Zadoks et al. (2005) reported that pauA-negative isolates may represent a novel subtaxon of S. uberis that is genetically closely related to S. parauberis, this could not be confirmed in our PI-1840 study. Finally, gapC, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was included because in several pathogenic bacteria GAPDH protein has been described as being associated with virulence (Ling et al., 2004; Maeda et al., 2004) due to its ability to bind several host proteins (Pancholi & Fischetti, 1992) or to confer resistance against reactive oxygen species produced by host phagocytic cells (Holzmuller et al., 2006). A recent study in Streptococcus agalactiae describes GAPDH as a virulence-associated immunomodulatory protein (Madureira et al., 2007). Furthermore, Perez-Casal et al. (2004) have suggested
that a GapC product may be a good target for S. uberis vaccine development. In the present study, the gapC gene was found in 79.4% of the strains. In conclusion, we found a large number of virulence patterns associated with intramammary infections. Different virulence patterns were found within the same herd and among herds, demonstrating that strains with different virulence patterns were able to cause mastitis. Despite the large number of strains with different virulence patterns, strains with identical patterns were found. Nevertheless, it is important to consider that S. uberis infections may be likely to be dependent on host factors. Detection of virulence-associated genes in individual S. uberis strains isolated from mastitis showed strains which carried one to 10 virulence genes.