Quorum sensing signals and related virulence inhibition of Pseudomonas aeruginosa by a potential probiotic strain's organic acid.

Studies conducted in recent years show that pathogen bacteria are not asocial assets and they use the cell to cell communication mechanism called quorum sensing that depends on population density to adapt changing environmental conditions. This mechanism is coordinate gene expression of various bacterial factors like bioluminescence, antibiotic biosynthesis, plasmid conjugation and virulence. Bacteria communicate with each other by producing signal molecules and regulate the production of virulence factors that have importance in the pathogenity formation. Virulence mechanisms of Pseudomonas aeruginosa, which causes various types of infections in humans, are also regulated by quorum sensing. Nowadays, biotechnological researches are focused on the development of homoserine lactone antagonists. The use of these type of molecules are considered to be a new treatment approach for blocking communication between bacteria and reducing virulence, therefore improving infection control. In this study, lactic acid of a potential probiotic Pediococcus acidilactici M7 strain isolated from newborn faeces was used to evaluate the inhibitory effect on quorum sensing signal molecules and some virulence factors of clinical Pseudomonas aeruginosa isolates. Results showed that lactic acid has an inhibitory effect on short-chain HSL production and swarming-swimming-twitching motility, elastase, protease, pyocyanin, and biofilm production of Pseudomonas aeruginosa isolates in certain quantities that are regulated by the quorum sensing system.