The lack of good production practices for fermented African oil bean seeds is a major setback in food safety standards of the product. African fermented oil bean seed is produced by cottage industries in ways defined by each producer, creating lapses that could lead to food contamination. These lapses in our vigilance for food safety have been responsible for outbreaks of serious food poisoning in different regions particularly in the continent of Africa (Campbell-Platt 1997; Olasupo et al. 2002). Our work seeks to draw attention to the issue of safety and quality of traditionally fermented foods in Africa.
The consumption of fermented African oil bean seeds in Nigeria dates back to centuries ago. However, the issue of safety remains a major challenge, like some other traditional fermented foods produced in Africa. The method for its preparation and fermentation has remained unchanged and, still depends mainly on spontaneous fermentation process and use of local non-sterile utensils. Other potential sources of variability in bacterial type and load could be the food handler’s hygienic status and lack of standardized manufacturing practice, leading to possible introduction of pathogenic organisms. The presence of some pathogens have been reported in fermented African oil bean seeds and this has included Escherichia coli and species of Staphylococcus, Klebsiella, and Proteus (Anyanwu et al. 2016; Eze et al. 2014; Isu and Njoku 1997; Ogbulie et al. 2014). Other pathogens that have been reported in other African fermented foods include Bacillus cereus, Salmonella sp. Vibrio cholera, Aeromonas sp., Campylobacter and Shigella (Gadaga et al. 2004). In a similar study on safety of traditional Nigerian fermented foods, Olasupo et al. (2002) reveals that microorganisms of public health concern that have been associated with Nigerian fermented foods include Staphylococcus aureus, Klebsiella sp., E. coli, Salmonella sp., Bacillus subtilis, and Enterococcus faecalis.
To ensure food safety, it is critically important that quality control standards including accurate methods for identifying pathogens be adopted and followed, in order to understand the extent of danger posed by the consumption of such food. Previous efforts in identifying possible pathogens in ugba have been predominantly culture-based, involving the isolation and identification methods using phenotypic tools. This identification scheme has the inherent weakness of not being able to detect and identify viable but unculturable organisms in a food matrix. The results obtained in this study using the phenotypic method of screening of cultured bacteria are consistent with what has been reported in the literature. However, as expected, DNA sequence based identification scheme employed in this study has shown that the range of organisms that could be of public health importance associated with ugba, could be much wider than what has been reported in literature and in this study, using culture-based methods. A variety of pathogens were reported, for the first time, in this study as being found in fermented African oil bean seed (ugba) using the PCR-clone library technique. Finally, while bacteria belonging to the genera Salmonella and Proteus have been associated with ugba in the past, their species-level identities were determined in the present study as Salmonella enterica and Proteus mirabilis respectively.
It is believed that molecular methods have a superior ability to detect and identify organisms that are viable but may not be culturable or are in very low numbers and could not be detected by pure culture isolation and phenotypic characterization. This accounted for the wider bacteria diversity and potential pathogens detected in this study. This belief is shared by Gao and Moore (Gao and Moore 1996); Schloss and Handelsman (Schloss and Handelsman 2005) who have demonstrated that molecular techniques, such as representational difference analysis, consensus sequence–based PCR, and complementary DNA library screening, have led to the identification of several previously unculturable infectious agents. Rhoads et al. (2012), in a study evaluating culturing versus 16S rRNA sequencing as tools for identifying bacterial species in human chronic wound infection, identified 145 unique genera using molecular methods, whereas only 14 unique genera were identified using aerobic culture methods.
Davey (Davey and Kell 1996) and Gunasekera et al. 2003 noted that a major disadvantage of using culture-based methods in the analysis of food samples is their failure to detect viable but non-culturable organisms. They raised doubts about the effectiveness of culture-based methods in the recovery of sub-lethally injured cells that may occur in heat treated products such as pasteurized milk. Since the fermentation process of ugba is usually terminated by boiling the final product in water, it is possible that the boiling process could have injured but not eliminated some of the bacteria and rendered them unculturable. However, because the molecular methods are culture independent, such cells are detected and identified. This and post fermentation handling and processing could therefore account for the wider range of bacteria diversity and potentially pathogenic bacterial genera/species detected by molecular techniques, against what was detected by cultural methods in ugba.
In addition to some other bacteria identified in literature, this study has reported for the first time various types of possible pathogenic bacteria in ugba including Enterococcus faecalis, Enterococcus casseliflavus, Enterobacter aeroginosa, Klebsilla pneumoniae, Salmonella enterica, Proteus mirabilis, Aeromonas sp. Enterobacter sp., Enterococcus faecium, Comamonas testosteronii and Clostridium sartagofum. Many of these organisms are part of the gastrointestinal microbiota of the human population, and their presence in the product is suggestive of fecal contamination. This is an indication of the poor hygiene in the processing environment and lack of good manufacturing practice. Fecal-oral route of transmission for many bacterial food-borne diseases is very significant; therefore, basic hygienic measures are an essential step for improving food safety. This study therefore, underscores the need to develop a standardized protocol for the production of this product, to ensure its quality and safety.
It remains possible that the presence of these bacteria of possible public health importance identified by this study is due to post-fermentation contamination. It is also possible however that their presence in ugba could be from the raw materials especially water, used in the production process. Since fermentation of African oil bean seeds has been shown to be an alkaline process, up to pH 8.2 (Ogueke et al. 2015; Olasupo et al. 2016), the antimicrobial effect often associated with most fermented food products due to their low pH is probably lacking in ugba. It is therefore possible that these organisms survived the fermentation process.
Whether the bacteria identified by this study were post-fermentation contaminants or they survived the fermentation process, their presence in ugba pose health risks to the consuming public. This is especially so as ugba purchased in the market place is sometimes eaten without pre-heating or cooking. Although, the enterotoxigenic potential of the detected organisms are yet to be determined, their presence in foods could serve as indication for the need to promote awareness about the possible health hazards due to handling and processing of traditional fermented foods.