Susceptibility of Malassezia pachydermatis to azole antifungal agents evaluated by a new broth microdilution method

Malassezia pachydermatis   is considered an opportunistic pathogen of the outer ear duct in dogs and cats. This yeast can also be found in the skin, rectum, anal sacks and vagina. Eighty-two samples of this yeast isolated from dogs with the symptoms of external otitis from the Porto Alegre region were tested for their susceptibility to antifungal agents using the Broth Microdilution Method. The testing antifungal agents were Ketoconazole, Fluconazole and Itraconazole. Experimental essays determined that Sabouraud dextrose broth supplemented with 1% Tween 80 was the most appropriate medium for culture, for a ten-fold dilutions for the inocula, and 48 hours as the interval of readings. The ranges of the Minimal Inhibitory Concentrations (MICs) for the 82 samples were (a) Ketoconazole, from 0.015 to 0.25 mg/mL (mean of 0.08 mg/mL), (b) Fluconazole, from 1 to 32 mg/mL (mean of 9.22 mg/mL), and (c) Itraconazole, from 0.007 to 0.125 mg/mL (mean of 0.05 mg/mL). The isolates of M. pachydermatis showed an excellent level of susceptibility to antifungal azole agents, with all strains being susceptible to Itraconazole, and with only 2.4 % and 3.7% being resistant to Fluconazole and Kketoconazole, respectively. The use of the broth microdilution method allows the assessment of the susceptibility of large numbers of samples from M. pachydermatis isolates to the most common antifungal agents. The proposed procedure is easy to perform and considerably inexpensive compared with other existing tests, which makes this a method of choice for laboratorial use. A standardization of procedures currently used in veterinary mycology laboratories is required. Consistent results among laboratories could greatly benefit the establishment of proper comparisons between studies on antifungal susceptibility and therapeutic trials

Dermatófitos e leveduras isolados da pele de cães com dermatopatias diversas

As micoses cutâneas, causadas principalmente pelos dermatófitos Microsporum spp. e Trichophyton mentagrophytes e pelas leveduras Malassezia pachydermatis e Candida albicans, são as doenças fúngicas mais freqüentes que acometem os cães. O principal objetivo deste estudo foi conhecer a ocorrência desses fungos na pele de cães com dermatopatias de origens diversas. Uma população de 250 cães, com diferentes dermatoses, foi avaliada clinicamente no Serviço de Dermatologia do Hospital de Clínicas Veterinárias da Universidade Federal do Rio Grande do Sul, Porto Alegre - RS, no período de março de 2000 a março de 2001. Esses animais foram submetidos ao teste da lâmpada de Wood e obtiveram-se amostras de pêlo e/ou escamas da pele para exame de microscopia direta e cultivo fúngico. Foram também realizados outros exames complementares, quando disponíveis, no intuito de estabelecer o diagnóstico das diversas dermatopatias. As culturas fúngicas resultaram: 49,6% sem isolamento e 50,4% positivas, sendo isolados 29,6% fungos sapróbios e 20,8 % fungos causadores de micoses cutâneas (13,2 % Malassezia pachydermatis; 5,6% Microsporum canis e 2,0% Microsporum gypseum). As prevalências das dermatopatias, distribuídas por grupos de doenças, foram as seguintes: 44,4% de origem imunopática; 20% parasitária; 12,4% complexo seborréia-disqueratinização; 11,2% bacteriana; 6,4% fúngica; 2,8% diversas, 2,0 % endócrina e 0,4% congênita e hereditária