Neem oil against Aeromonas hydrophila infection by disrupting quorum sensing and biofilm formation.

Aeromonas hydrophila is an opportunistic pathogen that can cause a number of infectious diseases in fish and is widely distributed in aquatic environments. Antibiotics are the main approach against A. hydrophila infections, while the emergence of resistant bacteria limits the application of antibiotics. Here, quorum-sensing (QS) was defined as the target and the inhibitory effects of neem oil against QS of A. hydrophila was studied. The results showed that neem oil could dose-dependently reduce aerolysin, protease, lipase, acyl-homoserine lactones (AHLs), biofilm and swarming motility at sub-inhibitory concentrations. Results of real-time PCR demonstrated that neem oil could down-regulate the transcription of aerA , ahyI and ahyR . Moreover, neem oil showed significant protections to A549 cells and a fish infection model. Taken together, these results indicated that neem oil could be chosen as a promising candidate for the treatment of A. hydrophila infections.