Benzalkonium chloride and polyhexanide disinfectant (F10 SC) requires off-label use for environmental disinfection to be effective against Nannizziopsis guarroi

Background

Nannizziopsis guarroi causes contagious dermatomycosis in lizards. Treatment failures are commonly encountered and may be related to the prolonged environmental persistence of this microbe. F10 SC, containing benzalkonium chloride and polyhexanide, is a commercially available disinfectant often used in management of reptile infections particularly by hobbyists and breeders.

Methods

Three molecularly confirmed isolates of N. guarroi were aseptically collected into aqueous suspensions and diluted to 2 fungal concentrations. Each concentration of each isolate was exposed to 3 dilutions of F10 SC (1:20, 1:100, 1:500) for a 10-minute contact time based upon product label recommendations. Culture growth on standard potato-dextrose agar after 10 days of incubation was assessed for characteristic colony growth and cytology evaluation for fungal elements. The experimental design included control conditions as well as biological and technical replication.

Results

All control conditions grew characteristic fungal colonies with fungal elements visualized cytologically. Both concentrations of all 3 isolates exhibited no growth after contact with the highest concentration of the disinfectant (1:20) however fungal growth was evident after contact with the lowest concentration of disinfectant (1:500).

Conclusions and clinical relevance

Environments exposed and/or contaminated with N. guarroi can be effectively disinfected using F10 SC for a contact time of 10 minutes. Exposure to living tissue has not been evaluated and cannot be recommended at this time. Further work evaluating F10 SC disinfection against clinically relevant microbes should be pursued.