Genome wide transcriptomic analysis identifies pathways affected by the infusion of Clostridium perfringens culture supernatant in the duodenum of broilers in situ.

Clostridium perfringens type A is the main etiological factor for necrotic enteritis, a multifactorial enteric disease that penalizes performance, health, and welfare of poultry. Lack of knowledge of host responses and disease pathogenesis is slowing down progress on developing therapies for disease control. A combined genomewide and targeted gene approach was used to investigate pathways and biological functions affected by the infusion of C. perfringens culture supernatant in the duodenum of broilers in 2 experiments. An in situ isolated loop of duodenum was prepared in anesthetized broilers of 3 wk of age (Exp. 1) and was infused either with crude C. perfringens culture supernatant (n = 7; treated), positive for necrotic enteritis B-like toxin (NetB) as determined by a cytotoxicity assay, or with a control preparation (n = 6; control). Birds were maintained alive for 1 h and then euthanized for tissue recovery. The use of the Affymetrix chicken genome array on RNA samples from loop tissue showed top biological functions affected by culture supernatant infusion included cell morphology, immune cell trafficking, and cell death; pathways affected included death receptor signaling, inflammatory response, and nuclear factor (NF)-κB signaling. In a second in situ study (Exp. 2), broilers were maintained alive for 4 h to monitor temporal expression patterns of targeted genes. Duodenal tissue was removed at 0.5, 1, 2, and 4 h post-infusion with culture supernatant (n = 9) or a control preparation (n = 5) for histology and gene expression analysis. Genes encoding proinflammatory cytokines, such as interferon γ (IFNγ), cell trafficking, such as neuroblastoma 1 (NBL1) and B cell CLL/Lymphoma 6 (BCL6), and cell death, such as Fas cell surface death receptor (FAS) and GTPase IMAP family member 8 (GIMAP8), were differentially expressed in the duodenum of treated and control broilers (P < 0.05). We have demonstrated that C. perfringens culture supernatant (NetB positive) infusion resulted in histological and gene expression changes consistent with necrotic enteritis in the duodenum of broilers. In the absence of live bacteria, crude culture supernatant resulted in early immunomodulation, inflammation, and cell death in the duodenum. The pathways identified here can be targeted for the development of new drugs, vaccines, and novel therapies for necrotic enteritis in broilers.

Heterogeneous shedding of Escherichia coli O157 in cattle and its implications for control.

Identification of the relative importance of within- and between-host variability in infectiousness and the impact of these heterogeneities on the transmission dynamics of infectious agents can enable efficient targeting of control measures. Cattle, a major reservoir host for the zoonotic pathogen Escherichia coli O157, are known to exhibit a high degree of heterogeneity in bacterial shedding densities. By relating bacterial count to infectiousness and fitting dynamic epidemiological models to prevalence data from a cross-sectional survey of cattle farms in Scotland, we identify a robust pattern: approximately 80% of the transmission arises from the 20% most infectious individuals. We examine potential control options under a range of assumptions about within- and between-host variability in infection dynamics. Our results show that the within-herd basic reproduction ratio, R(0), could be reduced to <1 with targeted measures aimed at preventing infection in the 5% of individuals with the highest overall infectiousness. Alternatively, interventions such as vaccination or the use of probiotics that aim to reduce bacterial carriage could produce dramatic reductions in R(0) by preventing carriage at concentrations corresponding to the top few percent of the observed range of counts. We conclude that a greater understanding of the cause of the heterogeneity in bacterial carriage could lead to highly efficient control measures to reduce the prevalence of E. coli O157.