Goel, ParveenMiakhil, Jahangir2017-08-052017-08-052009http://krishikosh.egranth.ac.in/handle/1/5810027567A study on the topic of “Investigations on prevalence and therapy of ear infections with special reference to Malassezia pachydermatis in dogs” was carried out during October 2008 to April 2009. The prevalence of M. pachydermatis in normal ears was found 37.94 per cent and 62.07 per cent in roll smear cytology and cultural examination, respectively and 46.88 per cent and 68.75 per cent in roll smear cytology and cultural examination, respectively was found in otitic ears. The microorganisms obtained from 64 otitic ears revealed that M. pachydermatis was the most common organism (68.75 %) followed by Staphylococcus spp., Pseudomonas aeruginosa, Proteus spp., E-coli, Streptococcus spp., Candida spp. and Aspergillus spp. Staphylococci were the main organisms isolated in association with M pachydermatis. It was observed that the highest (77.78%) of the cases of otitis externa associated with M. pachydermatis were reported during the months of October. The highest percentage of Malassezia otitis externa was recorded in dogs with age four to six years old where German shepherds was the most susceptible breed followed by Labrador, Spitz and Pug. In clinical cases of dogs with Malassezia pachydermatis ear infections, presence of brownish-black or yellowish colour and foul smelling purulent ceruminous exudate in external ear canal with pruritus was conspicuous. Microscopically, the cells of Malassezia pachydermatis were seen as oval to pea-nut Gram-positive unicellular yeast cells which reproduced by mono-polar budding on a broad base. SDA with and without chloramphenicol has been used for routine M. pachydermatis culture work. However, blood and nutrient agar failed to support the growth of M. pachydermatis. The Malassezia pachydermatis colonies were seen as convex, smooth, opaque, cohesive and crenated having pasty texture with entire edges. Biochemically, all the strains of M. pachydermatis were urease positive and weak catalase positive while no indole and coagulase production was noticed. All the strains were found negative for Methyl red, Voges-Proskauer reactions and nitrate reduction tests. Among the drugs used for treatment of otitis externa associated with M. pachydermatis the combination of chlorhexidine with fluconazole was recorded as superior compare to others. In in-vitro sensitivity tests, M. pachydermatis showed the most sensitivity in decreasing order of efficacy to ketoconazole, Nystatin, Fluconazole, Itraconazole and Clotrimazole antimycotics.enThesis