Antagonistic and Quantitative Assessment of Indigenous Lactic acid Bacteria in Different Varieties of Ogi against Gastrointestinal Pathogens

Introduction Ogi is a popular fermented cereal gruel consumed mainly in the western part of Nigeria. Traditionally, uncooked Ogi is normally administered to diarrhoea patients to reduce the frequency of stooling. This study was therefore undertaken to identify, quantify and determine the antimicrobial properties of lactic acid bacteria (LAB) isolated from Ogi. Methods The Ogi samples (Yellow, white, sorghum) were obtained from different market in Ibadan, Nigeria and Ogi control (cooked, uncooked and Omidun) were prepared with the viable counts of bacteria monitored over 5 days period. LAB were isolated from the varieties and identified by partial sequencing of 16S rRNA gene. The antimicrobial activities of the cell free supernatant (CFS) and the viable cells of the isolated LAB against Escherichia coli EC004, Salmonella sp. SS11, Shigella sp. SS10 were investigated by agar diffusion assay, agar overlay method, and coculture growth studies. Results Omidun had the highest LAB count while cooked ogi has the lowest LAB count. Weissella paramesenteroides , L. brevis, L. rossiae, L. fermentum, L. plantarum, Acetobacter pasteurianus, Paenibacillus sp. and Bacillus sp. were isolated from Ogi in this study. Large zone of inhibition (11≤x≤20) was observed with CFS against Salmonella sp. SS11 and Shigella sp. SS10 and also the overlay method. Coculture studies of Weissella paramesenteroides, Lactobacillus fermentum, and L. plantarum with Salmonella sp. SS11 showed a 5-8 log reduction of the pathogens' growth after 24 hours as compared with the control. Conclusion Ogi and its contents have antimicrobial properties against pathogenic organisms.


Introduction
The gastrointestinal microflora helps to maintain a microbial barrier against the colonization and proliferation of pathogens in the digestive tract [1]. Pathogens are responsible for inciting intestinal infections that negatively affect the normal functions of the gastrointestinal tract, leading to diseases such as cholera, typhoid, salmonellosis, acute gastroenteritis, traveller's diarrhoea and shigellosis. These aforementioned diseases are characterized by a common symptom known as diarrhoea. Diarrhoea is an illness characterized by stools in increased frequency and fluidity and it is one of the most common illness causing infant death in developing countries [2]. Consumption of contaminated food, poor hygiene, and close proximity to animals are the reasons why pathogens (such as Escherichia coli, Salmonella species, Shigella species, Staphylococcus aureus, Clostridium difficile and Campylobacter jejuni) find their way to the gastrointestinal tract [3]. Diarrhoea, although self-limiting, may sometimes require antibiotic therapy. However, most of the pathogens especially bacteria have already developed resistance to most of the conventional antibiotics [4]. Therefore it is necessary to look into scientific basis of some traditional remedy for diarrhea through the use of fermented foods that naturally contain beneficial microorganisms that will help to successfully compete with, and inhibit the growth of the gastrointestinal pathogens.
Ogi is an acid fermented cereal gruel made from maize or corn (Zea mays), sorghum (Sorghum vulgare,), and millet (Pennisetum americanum) [5]. It is the most popular traditional health-sustaining fermented food in Western Nigeria, and serves as weaning foods for infants in this region. Ogi consists of smooth cereal sediments and fermented water on top called Omidun. In some communities in southwestern Nigeria, raw ogi is normally administered to people suffering from gastroenteritis to reduce/minimize discomforts [6,7].
Lactic acid bacteria have been associated with the fermentation of Ogi and have been frequently isolated [8]. The nutritional benefits of Ogi, microbial diversity and the roles of fermenters against inoculated pathogens in ogi have been investigated extensively [8,9] but no information is available on antagonistic effects of LAB isolated from ogi against gastrointestinal pathogens in co culture.
Furthermore,, Akharaiyi et al [10] and Omemu and Omeike [11] investigated effect of heat on general flora in Ogi but no information exist on differing quantities of LAB in cooked, uncooked ogi and    paramesenteroides AFN004, L. fermentum AFN018, and L.
plantarum AFN021 inhibited the growth of the pathogens Salmonella sp. SS11 with 6-8 log reduction. The highest log reduction was exhibited by W. paramesenteroides AFN004 (7 log reduction) Figure   2. In another experiment where Salmonella SS11 has grown for 8 hours before introducing a selected active LAB (W. paramesenteroides AFN004), the LAB inhibited the pathogen by 4 log in comparison to the control Figure 3.

Discussion
One of the properties of probiotics is presence of viable cells in adequate amount to confer health benefits. In a country like Nigeria that lacks approved probiotic formulation in its market, then the health benefits of fermented foods can be considered in relation to quantities and qualities of the fermenting LAB. In this study, it was observed that omidun (the ogi supernatant) had the highest load of LAB followed by the uncooked ogi slurry while cooked ogi has the lowest number of viable LAB. These observations also reinforce the standard knowledge that cooking reduces beneficial microorganisms in foods. Uncooked ogi is normally administered to persons suffering from diarrhoea-related infections in order to reduce stooling frequency [6], however, Ogi is usually eaten cooked.  Great antimicrobial activities of LAB isolated from ogi against salmonella sp. in coculture.

Competing interests
The author declare no competing interest.

Authors' contributions
Ayorinde Oluwatobiloba Afolayan is responsible for acquisition and interpretation of data and drafting the article Funmilola Abidemi Ayeni is responsible for conception, design and interpretation of data and revising the article Werner Ruppitsch is responsible for acquisition of some data, drafting of some part of the manuscript.