Malassezia yeasts are considered to be an emerging and opportunistic pathogen in both humans and dogs. In dogs, Malassezia yeasts are frequently associated with ceruminous otitis externa and pruritic seborrheic skin disorders. These yeasts are commonly isolated in healthy dogs from the anal sacs, rectum, groin, and ear canals. Some breeds carry large amounts of Malassezia on the skin without any associated clinical signs. Basset hounds are one of the breeds with reported large numbers of yeast. This study was designed to confirm the high prevalence of Malassezia yeasts on basset hounds and to compare two sampling techniques to assess quantity and distribution of the yeasts. Cytologic samples were collected with strips of tape, and fungal cultures were obtained by direct contact with modified Dixon's medium.
Samples were collected from four sites: medial aspect of the left pinna, umbilical region, axilla, and perianal areas. The hair was clipped, and samples were obtained by the two techniques on adjacent areas of exposed skin. In one sampling technique, a piece of tape was firmly applied to the skin and gently removed to obtain cytologic samples. This was repeated three times. Each sample was stained and placed on a glass slide. For the other sampling technique, plates were filled with modified Dixon's medium. They were then applied and gently pressed against each anatomical area for 10 seconds. All plates were incubated at 32° C for 4 days before counting. Microscopic examination of a wet mount of the colonies stained with lactophenol blue cotton was used to identify yeast. Malassezia was found on all dogs, although population sizes varied according to site. As expected, fairly high numbers were isolated from clinically normal dogs.
COMMENTARY: Factors other than the absolute number of organisms probably play a role in the pathogenesis of Malassezia dermatitis. Nevertheless, the extensive colonization by Malassezia in these basset hounds may indicate why dogs of this breed are predisposed to Malassezia dermatitis.
Comparison of two sampling techniques to assess quantity and distribution of Malassezia yeast on the skin of basset hounds. Bensignor E, Jankowski F, Seewald W, et al. VET DERM 13: 237-241, 2002.
