This species is particularly problematic due to the fact that it is ubiquitous in the dairy environment (Bramley & Dodd, 1984). Although the prevalence of mastitis with contagious pathogens has been reduced by improved milking hygiene, this has had little effect on environmental species (Leigh et al., 1999). Despite the severe economic

impact caused by the high prevalence of S. uberis in many well-managed dairy herds, virulence selleck screening library factors associated with pathogenesis are not well understood and constitute a major obstacle for the development of strategies to control this important mastitis pathogen (Oliver et al., 1998). Several putative virulence-associated genes of S. uberis have been described. Among these, resistance to phagocytosis conferred by a hyaluronic acid capsule (Ward et al., 2001), plasminogen activator proteins such as PauA (Rosey et al., 1999), PauB Cell Cycle inhibitor (Ward & Leigh, 2002) and SK (Johnsen et al., 1999), lactoferrin-binding proteins (Moshynskyy et al., 2003), adherence to and invasion of epithelial cells mediated by SUAM (Almeida et al., 2006), CAMP factor (Jiang et al., 1996), a surface dehydrogenase protein GapC (Pancholi et al., 1993) and Opp proteins involved in the active transport of solutes essential for growth in milk (Smith et al., 2002) have been found. As yet, nothing has

been reported about the occurrence of virulence-associated genes among S. uberis isolates from cattle with mastitis in Argentina, and about the possible distribution of virulence patterns at various dairy herds. The aim here was to examine 11 putative and known virulence-associated genes by PCR in 78 S. uberis strains isolated from cattle with bovine mastitis in Argentina. In addition, the distribution of virulence patterns at various herds was determined.

Although many studies relating the distribution of one or a few virulence-associated Urease genes have been reported, to our knowledge this is the first study that investigates the presence of a greater number of virulence determinants. Milk samples were obtained from 2359 milk-producing cows. Seventy-eight isolates were collected from udders of 78 cows with mastitis (>250 000 cells mL−1) from 21 dairy herds (I–XXI) between 2005 and 2006. One to 17 isolates were isolated from each herd. The size of the herds included in the study varied from 79 to 204 cows. The isolates included in this study are representative of those that cause bovine mastitis in Argentina as they were obtained from the four major dairy provinces (Buenos Aires, Córdoba, Entre Ríos and Santa Fé) located in the east-central region of Argentina. The shortest distance between herds was 24 miles, and the greatest distance between herds was 203 miles.