The cutaneous microbiota and Nannizziomycosis in bearded dragons (Pogona vitticeps): Associations between infectious Nannizziopsis species and common bacterial pathogens.

Background: In bearded dragons (Pogona vitticeps), nannizziomycosis can cause skin lesions, ulceration and lethargy. Formally known as yellow fungal disease (YFD), nannizziomycosis has traditionally been attributed to various Nannizziopsis spp. identified via culture and referred to as Chrysosporium anamorph of Nannizziopsis (CANV).

Hypothesis/objectives: We hypothesized that the presence of Nannizziopsis does not always lead to nannizziomycosis, and that this disease may be caused by multiple pathogens or interactions between microbes (known as the cross-kingdom effect).

Animals: Thirty-one bearded dragons with suspected nannizziomycosis (unhealthy group) and 20 healthy bearded dragons.

Materials and methods: Next-generation sequencing (NGS) was used to explore the microbial interactions within the cutaneous microbiota of 51 bearded dragons.

Results: One unidentified species within the Nannizziopsis genus (Nannizziopsis sp.) was included in a co-occurrence analysis between 877 bacterial and 78 fungal species in the unhealthy group. Forty-one positive co-occurrences with Nannizziopsis spp. were seen, including Salmonella enterica (p = 0.001), an unidentified species within the Clostridiales order (p < 0.001) and a fungal species from the Cladosporium genus (p = 0.0261). Forty-nine negative interactions with Nannizziopsis spp. were seen, including Bifidobacterium adolescentis (p = 0.0478) and Corynebacterium durum (p = 0.0478).

Conclusions and clinical relevance: These findings suggest that commensal microbes may change in response to counteract Nannizziopsis, while pathogenic microbes may help facilitate it. Further research should clarify microbial interactions in bearded dragons with nannizziomycosis.