One of the concerns in food industry is the contamination of food by pathogens, which are frequent cause of foodborne diseases. Recurrent outbreaks of diarrhea and other foodborne illnesses combined with the natural resistance of the causative agents, is a huge risk to global health, food security and development (Caniça et al., 2019). Use of antibiotics in the control of such infections is faced with the challenge of resistance of pathogens to antibiotics as a result of misuse/overuse of antibiotics, incorrect dosing, low potency, poor solubility and lack of quick or accurate tests to diagnose infection (Castro-Sanchez, et al., 2016). Consequently, there is quest for alternative means to surmount this impeding danger. Nutrition was an essential component in many traditional forms of medicine (Georgiou et al., 2011), until the last century when its role in curative medicine started to decline. Following the increased awareness of the importance of lifestyle for disease prevention, we are now facing a reawakening of nutrition or lifestyle in general, for disease management and control (Witkamp and Norren, 2018).
A viable option is to opt for safe foods with less chemical additives and more of natural products which do not deter the organoleptic quality of the food or harm the consumers (Soltani et al., 2021). Biotechnology in the food-processing sector targets the selection, production and improvement of useful microorganisms and their products, as well as their technical application in food quality and control of food borne diseases. Generally, food with no additives is more desirable, but if not available, consumers will choose foods containing natural additives over synthetic equivalents (Coderoni and Perito, 2020; Perito et al., 2020). Bacteriocins produced by lactic acid bacteria, is of interest since they are safe, active in a nanomolar range, heat stable, readily digested by gastric enzymes and there is currently no reports of pathogenic bacteria developing antimicrobial resistance to them. Effective application in food preservation has been reported and till date no toxic effect has been attributed to their usage. Bacteriocins are multifunctional, ribosomally produced, proteinaceous substances produced by bacteria which are biologically active with antimicrobial action against other bacteria principally closely related species. They are normally not termed antibiotics in order to avoid confusion with therapeutic antibiotics, which can potentially elicit allergic reactions in humans with related medical problems (Deraz et al., 2005; Negash and Tsehai 2020). Bacteriocins differ from most therapeutic antibiotics in being proteinaceous agents and as such rapidly digested by proteases in the human digestive tract. Antibiotics are generally considered to be secondary metabolites that are inhibitory substances in small concentration, excluding the inhibition caused by metabolic by-products like ammonia, organic acids and hydrogen peroxide. It is likely that most if not all bacteria are capable of producing a heterogeneous array of molecules in the course of their growth in vitro (and presumably also in their natural habitats) that may be inhibitory either to themselves or to other bacteria (Ayivi et al., 2020). Bacteriocin production could be considered as an advantage for food and feed producers since, in sufficient amounts, these peptides can kill or inhibit pathogenic bacteria that compete for the same ecological niche or nutrient pool. This role is supported by the fact that many bacteriocins have a narrow host range, and is likely to be most effective against related bacteria with nutritive demands for the same scarce resources (Yang et al., 2018). Bacteriocins are often considered more natural because they are believed to have been present in many of the foods consumed since ancient times. Bacteriocins are inactivated by enzymes, such as trypsin and pepsin, found in the gastrointestinal tract and therefore do not alter the microbiota of the digestive tract (Balciunas et al., 2013; Negash and Tsehai 2020).
Despite the fact that antimicrobial peptides have an inhibition spectrum narrower than that of antibiotics, the bacteriocins produced by LAB have been reported to infiltrate the outer membrane of Gram-negative bacteria and lead to the inactivation of Gram-negative bacteria in combination with other enhancing antimicrobial environmental factors, such as organic acid, low temperature and detergents materials (Parada et al., 2007). Bacteriocins are generally named based on the genus or species of the strain producing it. For example, Lactobacillus plantarum produce plantaricin, Lactococcus spp. (lacticin, nisin), and Carnobacterium spp. (carnocin), Enterococcus spp. (enterocin) Leuconostoc spp. (leucocin) and Pediococcus spp. (pediocin) (Yusuf, 2013).
LAB are known to be Gram-positive, non-spore-forming rods, cocci and cocco-bacilli non-aerobic but aero-tolerant, able to ferment carbohydrates into energy and lactic acid (Jay, 2000). LAB belong to the phylum Firmicutes. The different major genera of LAB include: Carnobacterium, Lactobacillus, Lactococcus, Enterococcus, Melissococcus, Lactosphaera, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Weissella, Vagococcus, and Tetragenococcus. Other genera include: Aerococcus, Propionibacterium, Microbacterium, and Bifidobacterium. They are known to constitute the highest percentage of bacteria that display probiotic properties. Among compounds produced by LAB during lactic acid fermentations are: organic acids, diacetyl, hydrogen peroxide, and bacteriocins or bactericidal proteins (Yusuf, 2013).
These microorganisms are ubiquitous in nature, they were first discovered in milk (Carr et al., 2002). They are also found in meat, fermented products, fermented vegetables and beverages (Gallego and Salminen 2016). Humans and some other animals also harbor LAB (Amarantini et al., 2019) without causing disease in them. Thus, because of the incidence of foodborne diseases in humans and growing resistance of pathogens to most antibiotics, this study was designed to isolate and identify LAB and screen their bioactive properties against food associated antibiotic resistant bacteria.