Effect of Lactobacillus spp. cell-free supernatant against planktonic growth and biofilm formation of foodborne Escherichia coli isolates

Abstract

The aim of this work was to evaluate the anti-Escherichia coli effect of cell-free supernatant (CFS) of Lactobacillus spp. against planktonic and biofilm forms of foodborne isolates. Escherichiacoli strains (P12, P25, P35 and P36), previously isolated from fresh filets of fish, were subjected to antimicrobial susceptibility determination by the disc-diffusion agar method. Subsequently, the antagonistic effect between probiotic and pathogenic strains was determined by spot overlay assay. Finally, the CFS activity against pre-established (12 h) biofilms was demonstrated through biomass quantification by crystal violet staining and scanning electron microscopy (SEM). All isolates presented some pattern of resistance, primarily to ampicillin and tetracycline. Probiotic strains presented high antagonistic effects against all E. coli strains, presenting inhibition zones (R) ranging from 15.60 to 20.67 mm. Additionally, the residual biomass of pre-established (12 h) biofilm was drastically reduced about 50% after CFS treatment (P < 0.01). What can be noted by SEM images, which show less surface-attached cells of CFS-treated biofilms of E. coli (P12). Thus, cell-free preparations produced from Lactobacillus spp. may represent a tool in the battle against planktonic cells and biofilm forms of antibiotic-resistant E. coli.

In Vitro Effect of the Cell-Free Supernatant of the Lactobacillus casei Strain IMAU60214 against the Different Pathogenic Properties of Diarrheagenic Escherichia coli

“…Structural analysis of the biofilms through phase contrast microscopy imaging provided evidence of the ability of the components released in the CSF of L. casei IMAU60214 to inhibit the architectural development of biofilms formed by the DEC strains. It was also observed that the CSF from L. casei IMAU60214 exhibits a protective effect on HT-29 epithelial cells infected with the EAEC and EHEC strains, producing toxins such as Pet toxin and Shiga-like toxin (SLT), respectively [ 58 , 59 , 60 , 61 , 62 ]. In this regard, Navarro et al [ 63 ] showed that Pet secreted by strains of the EAEC pathotype induces morphological changes in the mucosa characterized by flattening of the intestinal villi with cell damage to the intestinal mucosa evaluated in an experimental rat ligated loop model.…”