, 1989, Ho et al., 1998, Polack et al., 1998, Baldinger, 1999 and Barber and Swygert, 2000). The involvement of these bacteria, especially Aeromonas spp. and P. aeruginosa on the development of severe and persistent secondary infection after tissue injury is well documented ( McManus et al., 1985, Semel and Trenholme, 1990 and Gang et al., 1999). In addition, many other types of bacteria present in the soil and aquatic environment can be involved in secondary infections ( van Elsas et al., 2011), and the extent of infection cause by them can be determined

by how many of them are present, their ability to survive on damaged tissue and to produce toxins able to induce cytokine release and destroy host cells ( Bhakdi et al., 1986, Lallier and Higgins, 1988, Paraje et al., 2005, Markov et al., 2007 and Domingos et al., 2009). Because of the considerable number of accidents mTOR inhibitor Caspase inhibitor caused by Potamotrygon spp. stingrays in the region of Três Lagoas, and the increasing importance of environmental Gram-negative bacteria as emergent pathogens responsible for secondary infections acquired in aquatic settings, the species of bacteria encountered in the mucus of P. motoro stingrays and in the Alto Paraná river water were

determined and their capacity to release toxins, cause injury to epithelial cells, resist antibiotics and survive in the presence of stingray venom was evaluated. Mucus and tissue extract samples were obtained from twenty four P. motoro stingrays collected in the upper end of the Alto Paraná river, in the region of Três Lagoas, Mato Grosso do Sul state (BR). Briefly, the stingrays were restrained and samples of the mucus that covers their external surface were collected with sterile swabs from three cAMP different regions of their dorsal area. The tissue extracts were obtained from integumentary tissue covering the sting as previously described ( Barbaro et al., 2007). The protein content of tissue extract pools (from

now on referred to as venom) utilized in this work was determined by bicinchoninic acid albumin method ( Smith et al., 1985), using bovine serum albumin (BSA) as a standard. The procedures involving animals were conducted in conformity with national laws and policies (protocol number CGEN 02001.005111/2008, SISBIO 15702-1). The environmental water samples were collected from the surface and the bottom of the Alto Paraná river at the same points where P. motoro stingrays were restrained for mucus sampling. The HEp-2 cell line used in this study was obtained from Institute Adolfo Lutz, São Paulo, Brazil, previously acquired from the American Type Culture Collection (CCL2). The mucus samples were collected with sterile swabs, placed in Cary-Blair transportation media and after 18 h of incubation at 37 °C, the bacterial strains were isolated in blood-agar plates.