ANTIMICROBIAL ACTIVITY OF LACTOBACILLUS SPP AGAINST UROPATHOGENIC BACTERIA

ROBLES, LR; FARIZANO, JV; RAPISARDA, VA; HEBERT, EM; GRILLO PUERTAS, M; VILLEGAS, JM

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

Urinary tract infections (UTI) remain a major medical problem in terms of the number of people afflicted each year. Although antimicrobial therapy is generally an effective way to eradicateseradicate these infections, a current problem is the increasing emergence of microbes resistant to antimicrobial agents. Uropathogens (UP) usually develop biofilms, resulting in persistent and chronic infections that are associated with resistance to antimicrobial therapy. The use of lactobacilli has been proposed as an alternative to prevent UTIs in the era of antibiotic resistance. Here, the potential antibacterial and antibiofilm activities of supernatants derived from five lactobacilli strains against different clinical urinary strains, isolated from patients of a public hospital of Tucumán, were investigated. First, Lactiplantibacillus paraplantarum CRL 1905, L. brevis CRL 1942, L. fermentum CRL 973, L. helveticus ATCC974 and L. acidophilus ATCC 4356 strains were grown in MRS for 24 h at 37 °C; cell-free supernatants (CFS) were obtained by filtration. Inhibitory activities of these CFS were assayed by the agar well diffusion assay. Based on the inhibition halo, all CFS displayed a strong antimicrobial ability against the different UP strains, but with variable degrees. Staphylococcus aureus EC1 and Escherichia coli EC7 strains were selected for further studies. The minimum inhibitory volume (MIV) of the different CFS against the indicated strains were determined using a broth microdilution assay. The five CFS inhibited both pathogenic bacteria, with a MIV of 25 % (v/v). However, the minimal bactericidal volume (MBV) values of these CFS were ≥ 50 % (v/v), killing 99.99 % of the bacteria. The effect of all CFS against biofilm formation by EC1 and EC7 strains were determined. Dilutions up to 6 % of the tested CFS significantly inhibited biofilm formation, when compared with the untreated control, observing an antibiofilm activity in a concentration-dependent manner. In addition, the biofilm disassembly capacity of all CFS on 72 h- established biofilms of the UP strains was assessed. When compared with the untreated control, a reduction of the integrity of biofilms using 10-fold concentrated CFS was observed. Finally, to determine the nature of the antimicrobial compound/s, the different CFS were submitted to heat, proteinase K and tripsine treatment, or neutralization. It was observed that all CFS lost their antagonistic properties after pH neutralization, suggesting an acidic nature of the metabolite/s. Our results demonstrate that CFS obtained from five lactobacilli strains secrete products that inhibit growth, reduce biofilm formation and remove established biofilm of different UP, suggesting their potential application for controlling or preventing colonization in UTIs.