Probiotic bacteria undergo specialised activities, including aggregation, cell surface hydrophobicity, adhesion to epithelial cells, and production of certain antimicrobial substances against pathogens. These activities enable them to exert their beneficial effects on their host. Selected lactic acid bacteria (LAB) and enteroaggregative E. coli (EAEC) previously isolated from traditionally fermented West-African cereal, ogi and unpasteurised fresh milk, respectively, were obtained studied for their abilities to aggregate and adhere to hydrocarbons. The LAB was further evaluated for their abilities to inhibit the EAEC. The LAB (Lactobacillus plantarum FS2 and Pediococcus pentosaceus D39) and EAEC demonstrated satisfactory cell surface properties and aggregation abilities with their EAEC counterparts. However, their auto-aggregation and co-aggregation were strain specific. Also, their adhesion to hydrocarbons and the exclusion of EAEC by LAB depended on the two bacteria involved and their incubation time. Neither LAB nor EAEC shows a correlation between auto-aggregation and adhesion, a requirement for colonisation and infection of the gastrointestinal tract. Likewise, there was no correlation between auto-aggregation and adhesion to Caco-2 cells and between hydrophobicity and auto-aggregation abilities for the two combatting bacteria. Therefore, the two LAB from traditionally fermented West African cereal, ogi, demonstrated promising properties worth considering for further applications in fermented functional foods and food products to improve human health.
The colonisation of the intestinal tract with the potential to exclude, displace and inhibit enteric pathogens is principally dependent on the adhesion ability of probiotics. Therefore, probiotic efficacy is mainly determined by their adhesion ability. The current study reports the antagonistic effect of four lactic acid bacteria (LAB) on the adhesion profile of four diarrhoeagenic with one non-diarrhoeagenic enteroaggregative E. coli (EAEC). All the bacterial strains investigated adhered to the Caco-2 cells. All the LAB tested competitively eliminated, displaced, and excluded at least three (non-) diarrhoeagenic EAEC strains from adhesion (P < 0.05). Lactobacillus plantarum FS2 exhibited the highest adhesion to the Caco-2 cells, competitive exclusion, displacement, and exclusion against most of the EAEC. Additionally, the competence to competitively exclude, displace and inhibit the EAEC from adhesion depending on the pathogens and the LAB strains tested signifies the participation of several mechanisms. Contrary to all the EAEC strains, gastrointestinal stress factors such as low pH (2.5) did not affect (P > 0.05) the adhesion of the LAB. Unlike the gastrointestinal acidic conditions, bile salt conditioning (at pH 6.5) did not affect (P > 0.05) the adhesion of both EAEC and LAB. In conclusion, all the LAB tested showed specific anti-adherence effects, including competitive exclusion, displacement, and exclusion against the selected EAEC. The results indicated that all the LAB, especially Lactobacillus plantarum FS2, had an excellent ability to exert antagonistic effects against the selected EAEC to prevent gastrointestinal infection.
The application of probiotics as an indispensable tool for prophylactic and therapeutic management of gastrointestinal infections caused by enteropathogens like Enteroaggregative Escherichia coli (EAEC) is evolving. Some Lactobacilli have been noted to inhibit enteropathogens’ adhesion to protect epithelial barrier integrity and function. This study focused on the ability of lactic acid bacteria (LAB) with promising probiotic characteristics from West-African traditionally fermented food, ogi, to attenuate diarrhoeagenic EAEC-induced changes to the intestinal epithelial barrier. Our results demonstrate that challenging polarised Caco-2 cell monolayers with the selected EAEC strains reduced trans-epithelial electrical resistance (TEER) and increased inflammatory cytokine, interleukin 8 (IL-8) secretions. However, treating the monolayers with Lactobacillus plantarum FS2 and Pediococcus pentosaceus D39 from ogi restored the deviations in TEER and IL-8 from the diarrhoeagenic EAEC’s damaging effects. Thus, the two LAB isolates conferred some protective effects on the intestinal epithelium and will protect and maintain its structure and function against the ravaging effects of the diarrhoeagenic EAEC, implying that they both have the potential to maintain and improve consumers’ gut health.
The application of probiotics as preventive medicine is emerging as an indispensable tool in managing foodborne infections and inflammatory bowel syndromes. The current study aimed to evaluate the in vitro prophylactic and therapeutic abilities of two lactic acid bacteria (LAB), (Lactobacillus plantarum FS2 and Pediococcus pentosaceus D39) against diarrhoeagenic enteroaggregative Escherichia coli (EAEC) induced damage to intestinal epithelial barrier function using Caco-2 cells. Intestinal cells exposed to EAEC demonstrated very low trans-epithelial electrical resistance (TEER) levels (2.50 ± 0.05 Ω.cm2) coupled with significantly higher (P < 0.01) phenol red flux levels contrary to controls and LAB (109 CFU/mL) treated cells. Nevertheless, the EAEC-induced hyperpermeability was significantly restored when the EAEC were competitively excluded, displaced, and inhibited by the two potential probiotic LAB. Meanwhile, significantly high numbers of EAEC cells (0.8 – 3.8 log10 CFU/ml) were recorded translocating across the differentiated Caco-cells when challenged with the former. In conclusion, L. plantarum FS2 and P. pentosaceus D39 restrained and restored EAEC-impaired intestinal barrier function by improving the expression and distribution of important tight junction proteins. Thus, they can be applied as indispensable food supplements and additives to address different diseases, particularly gut-related ones.
