Experimental infection of laying hens with Salmonella enteritidis strains that express different types of fimbriae.

A study was conducted to compare the pathogenicity of three Salmonella enteritidis phage type 8 strains (9, 21, and 30) in 30-wk-old laying hens. Strain 9 expressed two types of fimbriae of 14 and 21 kDa. Strain 30 expressed a single fimbrial type (21 kDa). Strain 21 did not express any fimbrial protein. Laying hens were divided into three groups of 35 each and each group was orally inoculated with a single S. enteritidis strain (1 x 10(8) cfu per bird). Significantly less intensive cecal colonization and fecal shedding of the organism were observed in hens that were inoculated with the strain that did not express fimbriae than in birds inoculated with other two strains (P < 0.05). Isolation of S. enteritidis from liver, spleen, reproductive organs, and egg contents did not differ between groups. Mean serum S. enteritidis lipopolysaccharide-specific antibody titers of birds inoculated with strain 21 were lower than titers of hens that were inoculated with the other two strains from the 5th wk through the end of the trial. Immunoblot of the bacterial outer membrane structures revealed the presence of serum antibodies against lipopolysaccharide, membrane-associated proteins, and purified 14 kDa fimbrial protein in birds inoculated with strain 9 as late as 9 wk postinoculation. Results of this study are consistent with a role for fimbrial proteins in the cecal colonization by S. enteritidis. In addition, cecal colonization mediated by fimbrial proteins may enhance the elicitation of humoral immune response against S. enteritidis.