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. Strai n 30 expressed a single fimbrial type (21 kDa). Strain 21 did not expr ess any fimbrial protein. Laying hens were divided into three groups o f 35 each and each group was orally inoculated with a single S. enteri tidis strain (1 x 10(8) cfu per bird). Significantly less intensive ce cal colonization and fecal shedding of the organism were observed in h ens 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 co ntents did not differ between groups. Mean serum S. enteritidis lipopo lysaccharide-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 o f the bacterial outer membrane structures revealed the presence of ser um 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 consiste nt with a role for fimbrial proteins in the cecal colonization by S. e nteritidis. In addition, cecal colonization mediated by fimbrial prote ins may enhance the elicitation of humoral immune response against S. enteritidis.