Spectrum and Frequency of Fungal Isolates Responsible for Subcutaneous Mycoses in Rural Rice-Farming Communities

Abstract

Background: Subcutaneous mycoses are chronic fungal infections of the dermis and subcutaneous tissues, often resulting from traumatic implantation of environmental fungi. Rice farmers are particularly at risk due to prolonged exposure to moist soil and plant debris. However, data on the spectrum and frequency of causative fungi in Nigerian rice-farming communities are limited. Objective: To determine the spectrum and frequency of fungal isolates responsible for subcutaneous mycoses among rice farmers in Ayamelum Local Government Area, Anambra State, Nigeria, and to evaluate their antifungal susceptibility patterns. Methods: A total of 407 rice farmers were screened for subcutaneous lesions suggestive of fungal infection. Suspected lesions were sampled for fungal isolation, characterized morphologically and molecularly, and tested for susceptibility to eight antifungal agents using the disc diffusion method. Results: Of the 407 farmers screened, 75 (18.4%) presented with suspected lesions, and 39 (52.0%) were confirmed positive for subcutaneous mycoses. Seven fungal species were identified: Meyerozyma carpophila (13.3%), Trichosporon asahii (17.3%), Limtongozyma siamensis (2.7%), Mucor indicus (4.0%), Penicillium brasilianum (5.3%), Pseudopestalotiopsis theae (4.0%), and Penicillium citrinum (5.3%). Prevalence varied significantly across towns, with Omor and Umumbo recording the highest infection rates (100% and 93.8%, respectively). Azole antifungals, particularly econazole and ketoconazole, showed the highest inhibitory activity, while fosfomycin exhibited no effect. Conclusion: Subcutaneous mycoses are an important occupational health concern among rice farmers in Ayamelum L.G.A., with yeasts such as Trichosporon asahii and Meyerozyma carpophila predominating. The observed species diversity and variable antifungal susceptibility underscore the need for accurate laboratory diagnosis and targeted therapy. Public health strategies to reduce occupational exposure and improve early detection are warranted.