G.H. Nardi; S.D. Coutinho
Laboratório de Biologia Molecular e Celular da Universidade Paulista, Curso de Pós-graduação em Imunopatologia Veterinária - UNIP, São Paulo, Brazil. Bolsa: CAPES-PROSUP
Malassezia pachydermatis is part of the microbiota of the mucosae and skin of mammals, but some conditions lead to its exacerbated growth, causing clinical disease, mainly otitis and dermatitis. Although malasseziasis represents an important disease in clinical practice involving small animals, especially dogs, the virulence factors and pathogenesis of the diseases caused by this yeast are still unknown. Production and secretion of exoenzymes have been established as factors of virulence for some bacteria and yeasts of the genus Candida.
Therefore, the objective of this study was to research the production of proteinase and phospholipase by M. pachydermatis isolated from cerumen of asymptomatic dogs and otic secretion from dogs with external otitis, in order to determine if there were differences in the production related to the origin of the samples, microbiota or otitis. Seventy isolates of M. pachydermatis were studied, 39 obtained from otic secretion and 31 from cerumen in dogs with and without otitis, respectively. Proteinase production was researched using bovine albumin as the substrate of culture medium, and phospholipase using egg yolk in the culture medium, methods already employed by verifying the production of those enzymes for Candida albicans. Statistical analysis was carried out to compare the production of the enzymes in the two groups. Concerning proteinase, 33/39 (84.6%) and 25/31 (80.6%) strains produced that enzyme from dogs with and without otitis, respectively. Phospholipase was produced by 24/39 (61.5%) and 20/31 (64.5%) of strains from dogs with and without otitis, respectively. No significant differences were observed between the groups concerning the production of proteinase and phospholipase. Although some researchers believe that the production of exoenzymes participates in the pathogenesis of this microorganism in host tissues, results obtained here suggest that these enzymes are not a determining factor in the infectious processes caused by M. pachydermatis. Other virulence factors may participate in the pathogenesis of these mycoses. Further studies in this area should be encouraged, since a better understanding of the host-parasite relationship would permit more adequate preventive and therapeutic measures in cases of malasseziasis.