The influence of environmental bacteria in freshwater stingray wound-healing

Invasion by bacteria can influence the course of healing of wounds acquired in aquatic environment. In this study, the bacteria present in Potamotrygon motoro stingray mucus and in the Alto Paraná river water were identified, and their ability to induce tissue injury and resist antibiotics was determined. Biochemical identification analysis showed that 97% of all bacterial isolates were Gram negative, Aeromonas spp., Enterobacter cloacae and Citrobacter freundii being the species most prevalent. Gelatinase and caseinase were produced by Aeromonas hydrophila, Aeromonas sobria and Pseudomonas aeruginosa strains. Erythrocyte hemolysis assay showed that A. sobria, A. hydrophila and to a lesser extent, other Gram-negative bacteria produced hemolysin. It was also observed that molecules released in culture by these bacteria were toxic to human epithelial cells. Antibiogram results showed that 68% of all bacterial isolates were resistant to at least one type of antibiotic, mainly B-lactams. Finally, it was demonstrated that although P. motoro venom was toxic to epithelial cells it did not influence bacterial proliferation. In summary, the results obtained in this work indicate that during the accident, the mucus of P. motoro and the environmental water may transfer into the wound pathogenic multi-resistant bacteria with the potential to cause severe secondary infections.