Caracterização de linhagens de enterococci e lactobacilli potencialmente bioprotetoras visando ao desenvolvimento de bioprocessos e produtos para a cadeia produtiva do leite

Abstract

This work aimed to characterize autochthonous strains of enterococci and lactobacilli with bioprotective potential against Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli and Enterococcus faecalis. To this end, 98 genetically non-redundant LAB strains, previously isolated from dairy products, were identified as lactobacilli (n=48) and enterococci (n=50) by PCR. After confirmation of genetic diversity by REP-PCR, the strains were identified by MALDI-TOF as Lactiplantibacillus plantarum (N=14), Lacticaseibacillus paracasei (N=12), Lacticaseibacillus rhamnosus (N=12), Lactiplantibacillus pentosus (N=4) , Limosilactobacillus fermentum (N=2), Lactobacillus jonhsonii (N=1), Lentilactobacillus hilgardii (N=1), Lentilactobacillus parabuchneri (N=1), Levilactobacillus brevis (N=1), Enterococcus faecium (N=31), Enterococcus faecalis (N=17) and Enterococcus durans (N=4). Identification was confirmed by PCR for L. plantarum, L. paracasei, L. rhamnosus and L. brevis. In in vitro bioprotection assays, enterococci strains were more effective against S. agalactiae, while lactobacilli strains inhibited S. aureus, E. coli and E. faecalis (p ≤ 5%). Greater bioprotective potential was observed in strains of Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus, Lactiplantibacillus pentosus, Lentilactobacillus hilgardii, Lentilactobacillus parabuchneri, Enterococcus faecium and Enterococcus faecalis. Evidence of inhibition by bacteriocin activity was observed in strains of L. plantarum (972), L. plantarum (794), one of E. faecalis (681) and two of E. faecium [7(23) and 15(74)], in which the loss of inhibitory activity was observed in the presence of proteolytic enzymes. All strains were analyzed for their resistance profile to the antibiotics penicillin G, ampicillin, vancomycin, gentamicin, streptomycin, tetracycline, chloramphenicol, erythromycin and clotrimoxazole and showed susceptibility to at least four antibiotics. Lactobacilli strains showed a high rate of resistance to Vancomycin (n=44, 91.6%) and Cotrimoxazole (N=22, 45.83%) presenting susceptibility mainly to the antimicrobials Chloramphenicol (N=43, 89.58%) and Erythromycin (N=43, 89.58%). Enterococci strains exhibited a higher rate of resistance to Erythromycin (N=23, 44.23%) and Penicillin G (N=21, 40.38%) with high susceptibility to Chloramphenicol (N=49, 94.23%) and Vancomycin (N=47, 90.38%). Two strains of L. plantarum (82 and 88), one of E. faecalis (18) and two of E. faecium (41 and 46) were chosen to continue research in future projects as they present greater bioprotective potential and evidence of harmlessness. More studies are needed to characterize the bioprotection mechanisms, as well as to guarantee the safety of these microorganisms before their use in the development of bioprocesses and/or industrial bioproducts.