Beyond Domestic Cats: Environmental Detection of Sporothrix brasiliensis DNA in a Hyperendemic Area of Sporotrichosis in Rio de Janeiro State, Brazil

In Brazil, sporotrichosis has transitioned from a rural to urban disease, driven by a shift in the initiation of infection from the accidental inoculation of organic matter to the traumatic implantation of the fungus by cats. Since the emergence of zoonotic sporotrichosis caused by Sporothrix brasiliensis, investigations have largely ignored the environmental habitat of the pathogen due to its association with domestic cats. Therefore, we investigated 18 environmental samples collected from rural areas of two cities where zoonotic sporotrichosis is endemic, but where domestic cats are scarce. We utilized traditional culture methods, and samples were also examined with two molecular methods used for the clinical diagnosis of sporotrichosis: a nested-PCR targeting the ITS region and a species-specific PCR targeting the calmodulin gene. No Sporothrix colonies were identified by traditional culture methods. However, the nested-PCR and the species-specific PCR for S. brasiliensis were positive for 18 and 5 samples, respectively. Sequencing revealed that positive results with the nested-PCR were due to non-specific amplification of other Ophiostomatales DNA, rather than Sporothrix spp. Three of the five amplicons from the species-specific PCR were suitable for sequencing and confirmed the presence of S. brasiliensis DNA. Hence, we confirmed that S. brasiliensis, as with other Sporothrix species, has an environmental habitat. Our findings underscore the challenges of nested-PCR for Sporothrix environmental studies and highlight that sequencing must follow PCR protocols to definitively identify Sporothrix spp. in environmental samples.

Automated summary

This study investigated 18 environmental samples collected from endemic areas of zoonotic sporotrichosis in Brazil, where domestic cats are scarce, and confirmed the presence of S. brasiliensis in the environment. The research highlights the challenges of nested-PCR in Sporothrix environmental studies, emphasizing the importance of sequencing to definitively identify the presence of Sporothrix spp. in environmental samples.