Bioactive compounds of Lactobacillus casei as anti-virulence agents against Pseudomonas aeruginosa

Background and Aim : Probiotics are among new agents that can target quorum sensing (QS) systems of drug-resistant bacteria. QS is a cell-to-cell signaling mechanism that enables gene regulation to control diverse physiological functions in bacteria. QS is a highly attractive target for the development of novel therapeutics. The present study investigated whether Lactobacillus casei might interfere with the pathogenic properties of Pseudomonas aeruginosa, in vitro.Methods : The minimum inhibitory concentration (MIC) of Lactobacillus casei subsp. casei PTCC ۱۶۰۸ filtrate (acid filtrate) was determined against P. aeruginosa ATCC ۲۷۸۵۳ and P. aeruginosa PAO۱. Filtrates were tested for their effects on the production of P. aeruginosa virulence factors controlled by the QS system (biofilm formation, pyocyanin and rhamnolipid production, swarming, swimming and twitching motilities). Besides, the effect of filtrate on the expression of QS genes including lasI/R, rhlI/R, pqsA/R as well as pelF (pellicle/biofilm glycosyltransferase PelF), lasB (elastase LasB) and toxA (exotoxin A) was evaluated by quantitative real-time polymerase chain reaction.Results : The MIC value was ۶.۲۵ mg/ml. Sub-MICS (۳.۱۲۵-۱.۵۶۲ mg/ml) demonstrated a statistically significant reduction of virulence factors including pyocyanin and rhamnolipid production. Biofilm formation, swarming, swimming and twitching motility were also reduced after treatment. rhlI/R, pqsA/R, pelF and lasB genes were down-regulated after treatment.Conclusion : The present research demonstrated that natural bioactive compounds of L. casei could reduce virulence in P. aeruginosa strains and may be introduced as prophylactic and/or therapeutic agents in P. aeruginosa infections.

کلیدواژه ها:

L. casei ، bioactive compounds ، P. aeruginosa ، QS-controlled virulence factors