Terminal restriction fragment length polymorphism (T-RFLP) analysis was conducted on the 16S rRNA genes of the bacterial communities colonizing the epithelial surfaces of the terminal ilea of open conventionally housed mice in an institutional small-animal facility. Polymeric-immunoglobulin-receptor-deficient (pIgR ؊/؊ ) mice that were unable to secrete antibodies across mucosal surfaces were cohoused with normal and otherwise genetically identical wild-type (C57BL/6) mice for 4 weeks. If secretory antibodies played a role in modeling the gastrointestinal microbiota, C57BL/6 mice would have had a more distinct and uniform microbiota than their pIgR ؊/؊ cage mates. The T-RFLP profiles of the bacterial communities were compared by using Sorensen's pairwise similarity coefficient, a newly developed weighted pairwise similarity coefficient, and on the basis of Shannon's and Simpson's diversity indices. No systematic differences were observed between the dominant components of the mucosa-associated bacterial communities of the terminal ileal walls of the two types of mice, indicating that secretory antibodies do not control the composition of this microbiota. Similar analyses of experiments conducted at two different times, between which the bacterial community composition of the mouse colony in the small-animal facility appeared to have changed, showed that differences could have been detected, had they existed.

Salmonella enterica serovar Typhimurium definitive type 2 (DT2) is host restricted to Columba livia (rock or feral pigeon) but is also closely related to S. Typhimurium isolates that circulate in livestock and cause a zoonosis characterized by gastroenteritis in humans. DT2 isolates formed a distinct phylogenetic cluster within S. Typhimurium based on whole-genome-sequence polymorphisms. Comparative genome analysis of DT2 94-213 and S. Typhimurium SL1344, DT104, and D23580 identified few differences in gene content with the exception of variations within prophages. However, DT2 94-213 harbored 22 pseudogenes that were intact in other closely related S. Typhimurium strains. We report a novel in silico approach to identify single amino acid substitutions in proteins that have a high probability of a functional impact. One polymorphism identified using this method, a single-residue deletion in the Tar protein, abrogated chemotaxis to aspartate in vitro. DT2 94-213 also exhibited an altered transcriptional profile in response to culture at 42°C compared to that of SL1344. Such differentially regulated genes included a number involved in flagellum biosynthesis and motility.

The humoral response to the gastrointestinal (GI) flora was analyzed in secretory Ig (sIg)-deficient polymeric IgR (pIgR)(-/-) mice and otherwise congenic C57BL/6 mice. While both strains carried an ileal flora of similar size and composition, increased bacterial translocation to mesenteric lymph node was demonstrated in pIgR(-/-) mice. Serum IgA was greatly increased in pIgR(-/-) mice compared with C57BL/6 mice and reacted with commensal organisms and food. Serum IgG levels in pIgR(-/-) mice were increased to 6-fold above that of C57BL/6 mice and included specificities that bound to selected flora antigens. The enhanced recognition of flora antigens in pIgR(-/-) mice was explored using ovalbumin (OVA)-specific CD4(+) T cells and feeding of low concentrations of OVA. Increased proliferation of transgenic T cells was observed in pIgR(-/-) mice, relative to C57BL/6 mice, suggesting elevated net uptake of protein antigens from the GI tract in the absence of sIg. These studies suggest that there is increased recognition of GI flora antigens by systemic antibodies in pIgR(-/-) mice, most probably as a result of increased access of antigens from the GI flora to the systemic immune compartment, and support the hypothesis that a major function of the secretory immune system is to return environmental antigens to mucosal surfaces.

No abstract

Campylobacter spp. are frequently carried by poultry, but they are not believed to cause significant disease in these animals. Modern poultry breeds have been selected to grow rapidly under intensive conditions, but recently, consumers have moved toward purchasing birds produced in higher welfare, free-range or organic systems. Birds reared in these systems tend to be a slower growing breed and are fed a different diet. Birds reared in such systems are stocked at a lower density compared with the standard conventional broilers, and they have access to environmental enrichment, such as perches. In previous research, these slower growing birds have been shown to have different levels of Campylobacter carriage in commercial rearing conditions, but the reasons for, and effect of, these different levels are unknown; is it the bird breed, diet, or environmental conditions? In this study, experimental flocks of fast- and slow-growing breeds of broiler chickens were reared to a standard commercial slaughter weight, with their weight gain being measured during the growing period. At 21 days, birds were either infected with Campylobacter jejuni or given a placebo as control. Cohorts of birds were euthanatized at various intervals, and samples were taken for examination for Campylobacter. The fast-growing birds gained weight more rapidly than the slow-growing birds. By 2 days postinfection (dpi), C. jejuni was detected in the caeca and by enrichment from the liver and spleen samples from both breeds of birds. Low-level colonization persisted in the spleen and liver samples but was undetectable by 28 dpi. Fast- and slow-growing birds did not show detectably different levels of Campylobacter carriage. Infection with C. jejuni affected the incidence of hock marks and pododermatitis in both breeds of birds, but the differences were greater with the fast-growing breed compared with the uninfected control birds. In addition, the incidence of pododermatitis was significantly higher in Campylobacter-positive fast-growing birds than in their slower-growing counterparts. The results show that infection with Campylobacter can have an indirect welfare effect on birds via increased incidence of hock marks and pododermatitis.