Antimicrobials from Native Lactic Acid Bacteria: A “Shotgun” Against Antibiotic-Resistant Staphylococcus aureus

Introduction The contamination of food by microorganisms, their persistence, growth, multiplication, and/or toxin production has emerged as an important public health concern. The demand for consuming fresh and low-processed foods free of chemicals and pathogens is increasing. Despite advances in food safety, annually, more than 9 million persons developed illnesses caused by food contamination (Scallan et al., 2011). In Ecuador, the risk of diseases associated with food contaminations is increasing due to incorrect food manipulation, hygiene, and inappropriate storage conditions (Garzon et al., 2017). Although the vendors are continuously capacitated, no improvement on selling sites was made. The food is continuously sold on the street, near parks, transportation terminals, as a common habit. Along with the excessive use of chemicals for preservation, food safety is of concern. To overcome this problem, the application of natural preservation methods might be a suitable solution. Lactic acid bacteria are producing peptides or small proteins namely bacteriocins which could be the next generation of antimicrobials. Thus, their incorporation in food to prevent poisoning or spoilage has been an area of dynamic research in the last decade (Backialakshmi et al., 2015). Previously, we identified two native bacteriocinogenic strains, Lactiplantibacillus plantarum UTNGt2 and L. plantarum UTNCys5-4, producing peptides with a broad spectrum of antibacterial activity against several foodborne pathogens in vitro (Tenea and Pozo, 2019; Tenea and Guana, 2019). Moreover, the addition of those peptide extracts at the exponential phase of growth of the target bacteria (Staphylococcus aureus ATCC1026) results in a decrease of total cell viability with about 3.2-fold (log CFU/ml) order of magnitude at 6 h of incubation, indicating their bactericidal mode of action. In this study, the possible mechanism of action against Staphylococcus aureus was investigated through a series of cell biology analyses such as membrane permeabilization, cell integrity, and structural changes of the target cells. Altogether, the results demonstrated the effectiveness of peptides produced by native lactic acid bacteria to kill Staphylococcus and further investigation is need it to prove the effect in a food matrix.