Abstract

Aeromonas hydrophila is a pathogen that causes disease in a wide range of homeothermic and poikilothermic hosts due to its multifactorial virulence. The production of many of these virulence determinants is associated with high cell density, a phenomenon that might be regulated by quorum sensing. The quorum sensing system regulates the expression of several virulence factors in a wide variety of pathogenic bacteria. To investigate the pathogenic role of quorum sensing system in A. hydrophila, We constructed an ahyI mutant strain of a fish-clinical isolate YJ-1, named YJ-1∆AhyI. Compared with the wild-type strain, the ahyI mutant strain exhibited a significant decrease of total extracellular virulent activity, and decreased in biofilm formation, intraperitoneal LD₅₀ of YJ-1∆AhyI were more than 10⁹ CFU, about 10⁴ times higher than the parent strain. These results suggest that A. hydrophila is able to regulate its extracellular virulent factors and biofilm formation by quorum sensing systems, and indicate that disruption of quorum sensing could be a good alternative strategy to combat infections caused by A. hydrophila.

Key words: Aeromonas hydrophila, quorum sensing, biofilm, virulence factors.