Culturable filamentous fungi isolated from apparently healthy Nile tilapia and targeted screening of aflatoxin biosynthesis-associated genes in representative Aspergillus isolates
Year: 2026
Type: article
Abstract: Filamentous fungi are ubiquitous in aquatic and aquaculture environments and may be relevant to fish health and food safety. However, information on culturable filamentous fungi recoverable from apparently healthy Nile tilapia ( Oreochromis niloticus ) in Egyptian aquaculture systems remains limited. This study investigated the genus-level composition, organ-associated distribution, and morphological characteristics of culturable filamentous fungi recovered from apparently healthy O. niloticus collected from commercial fish farms in Kafrelsheikh Governorate, Egypt. Five representative isolates phenotypically assigned to Aspergillus were selected for targeted PCR screening of the aflatoxin biosynthesis-associated genes aflR and aflP ( omtA ). A total of 210 apparently healthy fish were sampled from 11 commercial farms. Fungal isolates recovered from the gills, mouth, liver, spleen, and kidney were cultured on the selected fungal media and preliminarily assigned using conventional macroscopic and microscopic characteristics. Genus-level diversity was assessed using ecological diversity indices. Fish-level fungal recovery and the distribution of recovered isolates among anatomical sites were analyzed separately to account for the possibility of multiple fungal recoveries from individual fish. A total of 129 culturable filamentous fungal isolates representing 11 genera were recovered. Penicillium and Aspergillus were the predominant genera, accounting for 47.29% and 33.33% of the recovered isolates, respectively. Genus-level diversity indices indicated an uneven distribution of isolates among the recovered genera. At the individual-fish level, 118 of the 210 fish showed at least one fungal recovery, corresponding to an overall recovery proportion of 56.2% (95% CI: 49.4–62.7%). The recovered isolates were distributed predominantly in the gills (58.14%) and mouth (27.13%), which together accounted for 85.27% of all the recovered isolates, whereas fewer isolates were recovered from the liver, spleen, or kidney. Among the five screened isolates, aflP ( omtA ) was detected in all five (5/5; 100%), whereas aflR was detected in four (4/5; 80%). These findings demonstrate the presence of selected aflatoxin biosynthesis-associated genetic markers among the screened isolates but do not constitute molecular confirmation of their species identity, expression of the aflatoxin biosynthetic pathway, or actual aflatoxin production. This study provides a culture-dependent baseline of filamentous fungal genera recovered from apparently healthy O. niloticus under applied sampling and culture conditions. Further investigations should incorporate molecular taxonomic confirmation and direct assessment of mycotoxin production.
Source: Scientific Reports
Institutions: Agricultural Research Center, Kafrelsheikh University
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,690
OpenAlex ID: W7225743650