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Isolation of dematiaceous pathogenic fungi from a feed and seed warehouse
Abstract:
In an epidemiological study, nine isolates of dematiaceous fungi were recovered from the interior of a local feed and seed warehouse. Sample sites include brick walls and floors. Air samples also were included. Samples were collected in saline and plated on Mycobiotic and Sabouraud agar. The nine dematiaceous fungi recovered from these samples were identified with microscopic morphology, thermotolerance, biochemical reactions, and animal virulence test. Four isolates were identified as nonpathogens on the basis of positive gelatin tests. The identified pathogens included Fonsecaea pedrosoi, Cladosporium bantianum (C trichoides), Wangiella dermatitidis (Dixon et al., Mycopathologia 70:153-161, 1980), and Exophiala jeanselmei. These five organisms were injected into NCI/ALB mice. Only the isolate of C. bantianum was neurotropic, as demonstrated histopathologically and by the recovery of the organism from brain tissue. None of the remaining four isolates were seen or cultured from any of the mouse tissues analyzed. The recovery of pathogenic dematiaceous fungi from environmental sites is not uncommon. However, this study is noteworthy in that it represents only the second reported isolation of C. bantianum and the first isolation of F. pedrosoi from the environment in North America and suggests that these fungi may be more ubiquitous in this region that previously believed.
Insights
This study identified pathogenic dematiaceous fungi, including Cladosporium bantianum, in a warehouse. C. bantianum proved neurotropic in mice, suggesting wider environmental presence of these fungi in North America.
Area of Science:
- Mycology
- Epidemiology
- Environmental Microbiology
Background:
- Dematiaceous fungi are commonly found in various environments.
- Pathogenic species pose risks, necessitating understanding of their environmental distribution.
Purpose of the Study:
- To identify dematiaceous fungi in a local feed and seed warehouse.
- To assess the pathogenicity and neurotropism of isolated fungal species.
Main Methods:
- Epidemiological sampling of warehouse surfaces and air.
- Fungal isolation using Mycobiotic and Sabouraud agar.
- Identification via microscopy, thermotolerance, biochemical tests, and animal virulence assays.
Main Results:
- Nine dematiaceous fungal isolates were recovered.
- Pathogenic species identified: Fonsecaea pedrosoi, Cladosporium bantianum, Wangiella dermatitidis, Exophiala jeanselmei.
- Cladosporium bantianum demonstrated neurotropism in mice; other isolates were non-pathogenic in vivo.
Conclusions:
- This study reports the first environmental isolation of Fonsecaea pedrosoi and second of Cladosporium bantianum in North America.
- The findings suggest these pathogenic fungi may be more widespread in North America than previously thought.
- Environmental surveillance is crucial for understanding the distribution of potentially pathogenic fungi.