Microbial Safety and Contaminant Profile of Traditional Ugandan Fermented Foods: A Systematic Review and Meta-analysis of Pathogen and Mycotoxin Prevalence

Non-controlled spontaneous fermentation and high levels of pathogenic contamination make traditionally fermented foods such as bushera, malwa, and bongo an important source of dietary intake in Uganda, yet a potential threat to public health. However, a lack of fragmented scientific data has limited the comprehensive risk assessment of traditional fermented products. Therefore, the present review aimed to provide a systematic synthesis of available literature regarding major pathogenic bacteria (Salmonella spp., L. monocytogenes, E. coli, S. aureus) and mycotoxins (aflatoxins, fumonisins, OTA, DON) in the mentioned fermented products. Following PRISMA 2020 methodology, this systematic review included a search for peer-reviewed scientific articles published in the period from 2000 to 2024 in five databases (PubMed, Scopus, EBSCOhost, ResearchGate, Google Scholar). The search produced 854 articles. Only six papers passed the inclusion criterion. Their quality was evaluated using the JBI Critical Appraisal Checklist. Due to high heterogeneity (I2>75%), the review adopted a narrative approach. The results showed extremely worrying food safety issues associated with fermented beverages and cassava products. About 49.2% of the analyzed Obushera products did not conform to sanitary standards because of excessive amounts of E. coli and Staphylococcus spp. Moreover, more than 93% of the investigated fermented milk products were contaminated with potentially pathogenic microorganisms. As for mycotoxins, they occurred frequently with high concentrations; aflatoxin B1 content in cassava flour was equal to 27.1 µg/kg (exceeded by more than 5 µg/kg EU limit). A risk assessment indicated an increase of 3.44 new hepatocellular carcinoma cases (HCC) each year per 100,000 population in Northern Uganda attributable to aflatoxin exposure.