Survey on yeasts in mucosae of dogs with and without weakening pathologies

In human medicine many studies point out as yeasts, commensals on mucosae, can became pathogens in course of immunodeficiency, chemotherapy, cortisone therapy, endocrinopathies (Bulacio et al 2012, J. Mycol. Med., 22: 348-353). Such risk factors were also suggested in Veterinary Medicine but, so far, only few studies about this topic were made (Tampieri et al 2008, Parassitologia, 50: 95; Bieganska et al., 2012, 18th congress ISHAM, p.177). In this paper, the yeast flora of oral, conjunctiva and rectal mucosae of dogs was examined, in relation to presence (“sick dogs”) or absence (“healthy dogs”) of predisposing factors such as endocrinopaty, neoplasy, cortisone therapy or other weakening pathologies. One hundred eight dogs (61 “healthy” and 47 “sick”) were examined; from each dog 4 swabs from oral, conjunctival and rectal mucosae were collected and inoculated in duplicate on Sabouraud Dextrose Agar (BBL) with 0.05g/ chloramphenicol (Sigma). The plates were incubated both at 25°C and 37°C ad observed daily for 7 days. The yeasts isolated were identified microscopically for Malassezia pachydermatis and with Api 20C AUX (Biomerieux Italia S.p.a, Firenze, Italy) and Dalmau plates on Yeast Morphology Agar DIFCO (Becton Dickinson Italia S.p.a, Milano, Italy) for the other yeasts. Yeasts were found in 83 dogs out of 108 examined (76.8%). M. pachydermatis was isolated in at least one sample from 78/108 dogs (73.2%), especially in rectal mucosae where also the major number of yeast species was present. Conversely, lowest yeasts isolation was from conjunctival swabs. The other yeasts isolated were: Rhodotorula spp (8.34%), Candida albicans (3.7%), C. glabrata (2.78%), Cryptococcus laurentii (1.85%), C. guilliermondii, C. parapsilosis, C. boidinii, Saccharomyces cerevisiae and Cr. albidus (0.92%). M. pachydermatis was found more frequently in healthy dogs (83.6%) compared to sick dogs (57.4%) (X2y = 6.18p>0.05). On the contrary, other yeasts were found more frequently in sick dogs (15.22%) than in healthy dogs (6.2%) (Fisher exact p<0.05). In particular C. albicans, isolated only in 4 sick dogs (8.7%), was not found in healthy ones (Fisher exact p<0.05). In one dog with parvovirosis, C. albicans was isolated from an ulcer of oral mucosa which resolved without specific treatment after healing. M. pachydermatis was the yeast most frequently present on dogs mucosae, according to Tampieri et al. (2008 l.c.); Brito et al. (2009, Vet. J., 182: 320-326) and Santin et al. (2013), Braz. J. microbiol. 44: 139-143) and can be considered an usual component of mucosal microflora of dog. The isolation of S. cerevisiae could be explained by the administration of probiotics. C. boidinii, C. parapsilosis, Cr. laurentii, Cr albidus and Rhodotorula spp. isolated, with low number of colonies, only at 25°C, could be considered as environmental contaminants and not colonizer, contrary to C. glabrata and, especially, C. albicans that were isolated both at 25 °C and 37 °C, only in sick dogs and in high number of colonies. From these observations we can suppose that may be a real colonization of mucous membranes. Unlike what happens in humans, where C. albicans is a frequent commensal in the mucosa of healthy subjects, in the dog the finding of such yeast is occasional and could be a proof of organic imbalance.