Antimicrobial and antibiofilm activities of supernatants of Lactiplantibacillus plantarum A2 and Lactiplantibacillus plantarum 2.1 against Escherichia coli ATCC 25922

Background Urinary tract infections are the most common infections in humans. Furthermore, they are relevant for public health for being closely related to the phenomenon of dispersion of multi-resistant strains of bacteria. Most cases are caused by Escherichia coli , a commensal microorganism that colonizes the urinary tract by translocating from the gastrointestinal tract. In this context, the present work was dedicated to finding alternatives for controlling the dispersion of its multidrug-resistant strains by studying the inhibitory effect of the cell-free supernatants of Lactiplantibacillus plantarum A2 (LPA2) and Lactiplantibacillus Plantarum 2.1 (LP2.1). Among a group of eight strains isolated from cocoa fermentation, these two stood out in terms of their probiotic potential and possible applications in the health sector. This study conducted the in vitro investigation of the antimicrobial and antibiofilm activities of both supernatants and the preliminary analysis of their composition. Results Both supernatants evaluated showed antimicrobial and antibiofilm activity against E.coli ATCC 25922. In the semi-solid agar diffusion assay, LPA2 formed a 17 mm inhibition halo and LP2.1 formed a 12 mm one. In the 96-well microplate assay, LPA2 showed 89.22% inhibition and LP2.1 showed 91.22%. Regarding antibiofilm activity, LPA2 showed 80.96% inhibition and LP2.1 showed 81%. Preliminary analysis of the metabolites indicated that thermostable substances dependent on acidic pH may be responsible for the anti- E.coli action observed in the experiments. Conclusions LPA2 and LP2.1 supernatants are capable of antagonizing E.coli ATCC 25922 in vitro and can be used to control its proliferation in cases of asymptomatic bacteriuria, maintain the balance of the microbiota, and reestablish the microbiota after antimicrobial therapy.