Nannizziopsis guarroi has prolonged environmental persistence on clinically relevant substrates

To determine the environmental persistence of Nannizziopsis guarroi on clinically relevant solid and aqueous substrates.

2 molecularly confirmed isolates of N guarroi obtained from clinical cases of dermatomycosis in bearded dragons (Pogona vitticeps).

3 concentrations (1 McFarland, 1:10 McFarland, and 1:100 McFarland) of fungal suspension were exposed to 7 sterilized solid substrates (fabric aquarium liner, wood mulch, sand, hard plastic, glass, cotton, and stainless steel) and 2 sterilized aqueous substrates (distilled water, saline solution [0.9% NaCl]). Biological replicates were performed for the contamination of the solid substrates. On days 1, 3, and 14 after contamination, the substrates were sampled for fungal culture with technical repeat. Fungal cultures were incubated at room temperature for 10 days and then evaluated for fungal growth.

Data from wood mulch were not evaluated because of plate contamination. Overall, the ability to culture N guarroi from solid substrates was isolate, time, and fungal concentration dependent. Viable fungus was isolated from fabric aquarium liner and glass on day 1 and days 1 and 3, respectively. N guarroi was cultured from all other solid substrates at day 14 from at least 1 isolate and/or fungal concentration. Viable N guarroi was isolated from both aqueous substrates at day 14, regardless of isolate or fungal concentration.

The environmental persistence of N guarroi should be considered when treating lizards infected with this fungus. Fomites may contribute to the contagious nature of this pathogen and environmental disinfection should be performed to reduce transmission.