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Supernatants of the Probiotic Bacterial Cultures at sub-MIC Levels Attenuate Virulence of Pathogenic Bacteria Towards the Model Host Caenorhabditis elegans


Pooja Patel, Chinmayi Joshi and Vijay Kothari*   Pages 1 - 12 ( 12 )


Objective: This study assessed the anti-pathogenic potential of culture supernatants from three probiotic strains viz. Lactobacillus plantarum, Bifidobacterium bifidum, and Enterococcus faecium against five different gram-positive and gram-negative pathogenic bacteria.

Methods: The effect of probiotic culture supernatants on growth and production of quorum sensing (QS)-regulated pigments was assessed through broth dilution assay. In vivo anti-infective efficacy of these supernatants was evaluated by challenging the model nematode host Caenorhabditis elegans with pathogenic bacteria pre-treated with probiotic culture supernatants, and worm survival was monitored over a period of 8 days.

Results: All the probiotic culture supernatants (at 5-10 %v/v) exhibited bactericidal activity against four of the test pathogens (including three multi-drug resistant gram-negative bacteria) and they (at ≥ 1%v/v) could also modulate QS in pathogenic bacteria. Pre-treatment with culture supernatants from all the three probiotic strains were able to attenuate virulence of four of the test pathogens towards C. elegans. Worms challenged with supernatant-pre-treated pathogens recorded 75-100% better survival than those challenged with pathogens receiving no such pretreatment. Virulence-attenuating effect of the culture supernatants was also carried forward to daughter populations of the supernatant-treated parent pathogens. Lactic acid seemed to contribute notably towards anti-virulence activity of the culture supernatants, but acidic pH did not seem to be important for such activity.

Conclusion: Culture supernatants of probiotic strains used in this study can be said to possess appreciable virulence-attenuating potential. Further investigation for characterization of these supernatants and identification of the bioactive constituents is warranted. Elucidation of the molecular basis associated with the anti-pathogenic potential of these supernatants may lead to the identification of novel targets in pathogenic bacterial populations.


Quorum Sensing (QS); Anti-infective; Caenorhabditis elegans; Probiotic culture supernatants; Antimicrobial resistance (AMR); Post-supernatant effect.


Institute of Science, Nirma University, Ahmedabad- 382481, Institute of Science, Nirma University, Ahmedabad- 382481, Institute of Science, Nirma University, Ahmedabad- 382481

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