engleski

Disk diffusion susceptibility testing of Malassezia pachydermatis and Candida spp. isolated from animals against the three most commonly used antifungal drugs

Objectives: Malassezia yeasts are considered to be the inhabitants of skin microbiota of healthy animals and humans accompanied by Candida. Under certain conditions, they could become opportunistic pathogens where the most frequently isolated species is M. pachydermatis, causing otitis and dermatitis, mainly in dogs. Candida species might occasionally cause not only ear or skin infections, but also systemic infections in cats, dogs, horses, cattle, pigs, parrots and other animal species. In the past decade there is an increase in the number of reports of Candida spp. resistance and reduced susceptibility of M. pachydermatis in veterinary medicine. In addition, several case reports documented zoonotic transmission of M. pachydermatis to immunocompromised individuals. Taken together, these facts point to growing concerns about fungal resistance in human and veterinary medicine and suggest the need of regular antifungal susceptibility testing of human and animal isolates. The aim of this study was to examine the antifungal susceptibility of M. pachydermatis and Candida isolates originating from different animal samples submitted to Mycology laboratory of the Faculty of Veterinary Medicine in Croatia. Disk diffusion test was used for screening of susceptibility of isolated species against most commonly used antifungal drugs in clinical settings: miconazole (MCZ) and clotrimazole (CTZ) for topical treatment and itraconazole (ITZ) for systemic therapy. Methods: Swab samples were plated on Sabouraud dextrose agar (SDA) with the addition of chloramphenicol. M. pachydermatis strains were identified by conventional laboratory methods and their ability to grow on SDA without lipid supplementation. The identification of Candida isolates was based on their phenotypic characterization and molecular methods using the universal ITS-1 and ITS-4 primers for amplification of the internal transcribed spacer 1 (ITS1), ITS2 regions and the 5.8S ribosomal DNA region followed by sequence-based identification. Susceptibility of Candida isolates was determined as described by the CLSI M44-A2 method using MCZ, CTZ and ITZ disks (10 µg, Neo-Sensitabs, Rosco, Denmark). Because the standard procedure for Candida susceptibility testing cannot be applied to M. pachydermatis, recommended modified protocol was used. The results were interpreted according to manufacturer’s guidelines. Results: A total of 175 M. pacyhdermatis and 10 Candida species (four C. albicans, two C. tropicalis, two C. palmioleophila, one C krusei and one C. lusitaniae) were recovered from different animal species. Using modified disk diffusion test one isolate of M. pachydermatis showed reduced susceptibility to all three antifungal drugs tested. In addition, one isolate showed reduced susceptibility to CTZ, and three isolates to MCZ. All Candida isolates were susceptible to CTZ, five showed simultaneously resistance to MCZ and ITZ, and two isolates to ITZ alone. In both yeast species, the highest susceptibility was detected to CTZ. Despite the small sample size, the fungal antifungal susceptibility pattern showed that Candida isolates were more frequently resistant to tested antifungal drugs. Conclusion: Results of this study showed the presence of potentially resistant yeast isolates from animals. In order to obtain a detailed insight into their resistance pattern and the appropriate choice of antifungal treatment, further tests using broth microdilution method need to be performed.

Malassezia pachydermatis, Candida spp., disk diffusion susceptibility testing, animals

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