Antibacterial activity and molecular characterization of probiotic lactic acid bacteria isolated from traditional Moroccan fermented milk

Abstract

The multidrug resistance of pathogenic bacteria is considered a real health problem that can sometimes preventing the selection of an appropriate cure, or limiting the choice of antibiotics that can treat infections caused by these bacteria. The main cause of the ever-increasing spread of this problem is the widespread and repeated use of antibiotics. In light of this threat, finding an alternative to antibiotics has become crucial. In this context, our study focuses on selecting of 10 lactic acid strains with inhibitory capacity against multidrug-resistant pathogenic bacteria and enteropathogens producing beta-lactamase, which are too involved in several serious diseases. Of the 32 isolated lactic acid bacteria (LAB) strains, 10 exhibited significant antibacterial activity. The most active strain was Lactobacillus plantarum LB5, which exhibited an inhibition zone of 20.0 ± 0.0 mm against MRSA. All of the selected isolates were Gram-positive, catalase-negative bacilli and were classified into seven species, including L. acidophilus, B. longum, L. reuteri, L. rhamnosus and L. plantarum . Molecular identification confirmed the accuracy of the phenotypic results. CFSs remained active after heating at 100°C for 20 minutes and across a wide pH range (2–10). Enzymatic treatment with protease eliminated the antibacterial activity, thus confirming the proteinaceous nature of the compounds. The CFS of L. plantarum caused a significant increase in the OD260 and OD280 values, indicating membrane damage and intracellular leakage in the target pathogens.These findings emphasize the potential of bacteriocins produced by LAB as natural bio-preservatives and as an alternative to conventional agents against multidrug-resistant pathogens.