Antimicrobial photodynamic therapy for infectious stomatitis in snakes: Clinical views and microbiological findings

Background: Antimicrobial photodynamic therapy (APDT) has been broadly investigated as an alternative to treat localized infections, without leading to the selection of resistant microorganisms. Infectious stomatitis is a multifactorial disease frequently reported in captive snakes characterized by infection of the oral mucosa and surrounding tissues. In this study, we investigated methylene blue (MB)-mediated APDT to treat infectious stomatitis in snakes and verified the resistance phenotype and genotype before and after APDT. Methods: Three Boid snakes presented petechiae, edema and caseous material in their oral cavities. MB (0.01%) was applied on the lesions and after 5 min they were irradiated using a red laser (lambda = 660 nm), fluence of 280 J/cm(2), 8 J and 80 s per point, 100 mW, spot size 0.028 cm(2) and fluence rate of 3.5 W/cm(2). APDT was repeated once a week during 3 months. Samples of the lesions were collected to identify bacteria and antibiotic resistance profiles. To analyze the clonality of bacterial isolates before and after APDT, isolates were subjected to ERIC PCR analysis. Results: Snakes presented clinical improvement such as reduction of inflammatory signs and caseous material. Pseudomonas aeruginosa and Escherichia coli were present in all snakes; Klebsiella pneumoniae and Morganella morganii were also identified in some animals. We also observed that the oral microbiota was completely replaced following APDT. However, K. pneumoniae isolates before and after APDT were a single clone with 100% of genetic similarity that lost resistance phenotype for seven antibiotics of four classes. Conclusions: These results show that APDT can be used to treat infectious stomatitis in snakes.