Effect of sodium chloride and temperature on biofilm formation and virulence of Flavobacterium columnare isolated from striped catfish (Pangasianodon hypophthalmus)

Abstract

This research was conducted to investigate the biofilm formation ability at various salt concentrations and temperatures of Flavobacterium columnare isolated from striped catfish (Pangasianodon hypophthalmus) at Can Tho University. Microtiter plate assay and the in vivo challenge were used to test the virulence of this strain of F. columnare for 10 days by immersion method at different salt concentrations (0, 3, 6, 9, 12 and 15 ppt). Results showed that biofilm formation of F.columnare was inhibited at 3 and 6 ppt and stronger reductions were recorded at 9, 12 and 15 ppt. In the same trend, the higher temperature the lower biofilm formation, the highest biofilm formation was at 25°C treatment, then it was reduced at 28 and 31°C and at 35°C the formed biofilm was greatly reduced. Interestingly, there were no statistically significant differences between 28 and 31°C (P>0.05). The virulent study found that 100% fish died after 1 day post challenge at 0 ppt. There were 10% and 25% of fish died at 3 and 6 ppt respectively. No dead fish was found at 9 and 12 ppt. In conclusion, biofilm formation was inhibited at 3 ppt, was almost controlled at 9, 12 and 15 ppt and was also mostly reduced at 31°C at least in the in-vitro study. Furthermore, the virulence of this bacterial strain was controlled 90% at 3 ppt and completely controlled (100%) at 9, 12 and 15 ppt.

Keywords

• Biofilm formation
• Flavobacterium columnare
• immersion
• salinity
• temperature