Salmonella enterica Serovar Pullorum causes acute or persistent infection in chickens, resulting in significant economic losses. The objective of this study was to evaluate the biofilm-forming ability of S. enterica Serovar Pullorum strains and association with the pathogenicity. A total of 62 S. enterica Serovar Pullorum isolates were measured for biofilm formation by crystal violet staining. Thirty-nine out of 62 strains were found to produce biofilm which were further confirmed by observation under light microscopy, field emission scanning electron microscopy. Analysis of the major components for biofilm formation showed that bacterial colonies were smooth phenotype and the architecture of biofilm was composed of exopolysaccharides and curli other than cellulose. In addition, animal experiments were performed to determine the 50% lethal doses (LD50) of four S. enterica Serovar Pullorum isolates with or without biofilm-producing ability. Although the virulence of S. enterica Serovar Pullorum strains was independent of the ability of biofilm formation, prior growth as a biofilm for a biofilm producer of S. enterica Serovar Pullorum lead to enhanced virulence in chickens. The results suggested that biofilm may be one of the important virulence factors for S. enterica Serovar Pullorum infection.
Key words: Salmonella enterica Serovar Pullorum, biofilm, curli, virulence.
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