Atividade antibacteriana de porfirinas tetracatiônicas frente às bactérias isoladas de otite canina

Abstract

Canine otitis externa is a multifactorial disease commonly found in veterinary practice and it is estimated to affect up to 20% of dogs. The most important bacterial agents considered pathogens as a cause of otitis externa in dogs are Staphylococcus sp., Pseudomonas sp., Escherichia coli and Proteus sp. Bacteria resistant to traditional antimicrobials increasingly in cases of canine otitis, so the challenges are fight against these resistant bacteria. Porphyrins are photosensitizing molecules capable of interacting with light in order to generate reactive oxygen species that have the ability to alter structures and functions of cells and microorganisms, causing apoptosis and inactivation. Photodynamic therapy is a method that can be applied in many areas, such as the elimination of microorganisms in fluids and contaminated solutions, surfaces and materials, as well as in infections, especially caused by antimicrobial resistant bacteria. The objective of this study was to identify the most frequently isolated bacteria from ear swab cultures of dogs with otitis in the central region of Rio Grande do Sul state and to evaluate the antibacterial activity of two tetra-cationic metalloporphyrins (H2TMeP and ZnTMeP) in Gram-positive and Gram-negative bacteria isolated from dog otitis and standard strains. For this, initially a survey of the genera of bacteria most frequently isolated from these cases was performed. The most frequently isolated genera of bacteria were Staphylococcus sp., Pseudomonas sp. and Proteus sp. Antibacterial activity assays were performed by incubating a non-cytotoxic dose of porphyrins observed in MDCK cells (5μM to H2TMeP and ZnTMeP) against a fixed concentration of each of the selected bacteria, approximately 1x104 CFU / mL, and exposing this solution to artificial light (25 mW / cm2) for 0, 30, 60 and 90 min for porphyrin photoactivation. After light exposure, 10 μL of Grampositive bacteria solution and 50 μL of Gram-negative solution were seeded and incubated for 24 hours at 37 °C. The following day, the colony forming units were counted. Coagulasepositive staphylococci and coagulase-negative were inactivated after 30 min of light exposure. For Gram-negative bacteria, inactivation occurred after 60 min of photoactivation using H2TMeP and 90 minutes by ZnTMeP. In addition, it has been proven through the use of reactive oxygen species scavengers that the action of these porphyrins probably occurred by the production of singlet oxygen. The results show that ZnTMeP and H2TMeP tetra-cationic porphyrins have bactericidal activity against the main bacteria isolated from dog otitis, and may be promising options to be used as alternative control and treatment of clinical otitis with bacterial etiology resistant to conventional antimicrobials.