**9. Considerations**

*Canine Genetics, Health and Medicine*

HIV-positive patient [44]*.* Samples of this yeast were isolated for the first time in the oral cavity of stray dogs and demonstrated significant resistance to the antifungal fluconazole. In addition to this species, *Candida krusei* also obtained partial results of resistance to this antifungal, as well as yeasts of the genus *Trichosporon* spp. [9]. Itraconazole is a synthetic triazole derivative with a wide spectrum of action, widely used in the treatment of superficial mycoses by candidiasis, malasseziosis and in systemic mycoses. When used orally right after a meal, its bioavailability is maximum, with biphasic elimination. This antifungal has also been used successfully in dogs with mycotic rhinitis and in systemic mycoses, such as blastomycosis. However, its use in dogs can lead to skin rashes and, in high dosages, it can cause anorexia and increased plasma concentration of alkaline phosphatase and aminotransferase enzymes [43]. In addition, species isolated from the oral cavity of dogs (especially *Candida albicans* and *C. tropicalis*) have shown dose-dependent sensitivity to itraconazole. Yeasts of the genus *Trichosporon* also isolated from this active site, show medium resistance to fluconazole and significant resistance to itraconazole, which reveals concern about the use of these drugs in the treatment of candidiasis and triconosporoses in dogs [9, 19]. In the veterinary medical clinic, miconazole is commonly indicated for the treatment of dermatophytosis, malasseziosis and candidiasis. However, yeasts of the genus *Trichosporon* and *Malassezia pachydermatis* isolated from the oral cavity of dogs show important resistance to this antifungal. Different for *Candida* yeasts, in which the antifungal profile demonstrates sensitivity to miconazole [9, 19].

Caspofungin is an antifungal with an inhibitory action on the cell wall of the echinocandin group, important in human medicine as an alternative for the treatment of isolates resistant to fluconazole [45]. Against yeasts isolated from the oral cavity of dogs, yeasts of the genus *Trichosporon* and of the genus *Malassezia* demonstrate significant resistance to this antifungal, resistance also demonstrated

In cases of systemic infections, affecting different species of animals, the use of amphotericin B, a drug that acts on the fungal cell membrane, has efficiency against strains of *Candida* spp. However, due to the high cost and serious side effects, such as hepatotoxicity, nephrotoxicity, myelotoxicity and cardiotoxicity, this medication

Due to the great similarity between the fungal cell and the host cell, the action of antifungals presents relatively high toxicity. Thus, there is a need for research for the best choice of antifungal, based on the most appropriate therapeutic response and on the sensitivity profile of yeast against antifungal floodgates, seeking as well to minimize the side effects that can be generated with the use of more drugs

When information is obtained that a street animal, which in general is a dog that, has never received therapeutic treatment based on antifungal, presents positive isolation for resistant yeasts, it is assumed that environmental yeasts are undergoing an important primary resistance or that the ecological niche in which that animal lives is contaminated by resistant microorganisms originating from

Corroborating this fact, we must consider the excessive use of pesticides in the environment and mycoherbicides (placed in plantations, vegetable gardens, and in the soil itself), have a chemical constitution like azoles, thus representing a strong selective pressure for the emergence of strains resistant. This question of possible environmental contamination and fungal resistance is already discussed for other yeast species, such as *Cryptococcus* spp. and medical mycology becomes an important issue. The growing data on increased resistance of fungi against antifungal drugs have been causing great concern for human and veterinary doctors. Although data on resistance to antifungals from yeasts isolated from dogs are scarce, their importance

to a lesser extent by the species *Candida parapsilosis* [9, 19].

needed in cases of therapeutic failure [43].

direct or indirect human contamination.

**106**

is seldom used [17].

The oral cavity is an extremely important anatomical area of dogs, considered as one of the determining factors in the longevity of this animal's life. To reduce therapeutic failures and guarantee the perfect health condition of this system, knowledge of the existing microbiota is essential, but it is still scarce.

We can then ask ourselves: Why are recurrent fungal infections more and more frequent in dogs? What is the relationship between the microbiota of dogs and their respective owners? And what is the relationship of resistance to fungal infections between these species?

Possible answer to these questions could be founded in this chapter, as well as the beginning of the knowledge of the main yeasts found in the oral cavity of dogs, their clinical importance and profile of resistance to the main antifungals used in the practical routine of veterinary medicine.
