Rafael Rodrigues Ferreira

Genetic variability and phospholipase production of Malassezia pachydermatis isolated from dogs with diverse grades of skin lesions

Little detailed information is available on the association of Malassezia pachydermatis genotypes and the extent of skin damage that they cause. In the present study, isolates of M. pachydermatis, recovered from the skin of healthy dogs and dogs with dermatitis in Brazil, were characterized on the basis of partial sequencing of the large subunit (LSU), first internal transcribed spacer (ITS-1) and chitin synthase 2 gene (chs-2). The determination of phospholipase production was also included in the investigations. The severity of lesions and hyperpigmentation of dogs with skin disease were evaluated. For each locus, two main sequence types were designated as genotypes A and C. Two other minor sequence types (A2(I)-C2(I)) were also recorded and defined for the ITS-1. Genotype A isolates were the most prevalent, being recovered from healthy and diseased animals. No significant difference was detected among genotypes or ITS-1 sequence types and grades of skin damage or hyperpigmentation in the dogs with skin lesions. The number of M. pachydermatis isolates that produced phospholipase was statistically higher for diseased dogs than for strains found in healthy animals. The present study reveals that multiple genetic variants of M. pachydermatis occur in dogs and that the distribution patterns of particular genotypes on the skin of dogs in Brazil might be related to environmental and ecological factors which maintain distinctive genotype assemblages in specific geographical areas.

Malassezia dermatitis in dogs in Brazil: diagnosis, evaluation of clinical signs and molecular identification

Skin carriage and quantification of Malassezia yeasts were evaluated in 180 healthy dogs (group 1) and 117 dogs with clinical signs (pruritus, erythema, lichenification/seborrhoea, excoriations and alopecia) that could be related to Malassezia dermatitis (group 2) in Brazil. The lesions in the group 2 dogs were evaluated using CADESI-03 scores. Samples were collected from five different anatomical areas. Direct examination was performed using the tape strip technique, and results were expressed as the mean number of yeasts per ×1000 microscopic field per dog. For mycological culture, a single piece of sterilized carpet was applied to the same areas sampled for cytology, and transferred onto Dixons modified medium. Yeast populations were expressed as mean colony forming units (CFU)/plate. Malassezia isolates were characterized by polymerase chain reaction-restriction endonuclease analysis of the large subunit (LSU) of ribosomal RNA gene. The probability of culturing Malassezia from dogs with skin lesions was significantly higher (P<0.001) than from healthy dogs. There was a linear trend between CADESI-03 score and mean CFU/plate. Group 2 dogs with positive cultures had higher CADESI-03 scores than those with negative cultures (P<0.05). Almost all isolates were identified as Malassezia pachydermatis. Only one isolate (group 2) was identified as Malassezia furfur. These data suggest that dogs with skin disorders harbouring Malassezia yeasts in quantities higher than 120 mean CFU/plate should be considered as having Malassezia dermatitis. The presence of Malassezia appears to exacerbate clinical lesions in dogs.