Bacterial Challenge Model Research Articles

Chicken intestinal organoids: a novel method to measure the mode of action of feed additives.

There is a rapidly growing interest in how the avian intestine is affected by dietary components and feed additives. The paucity of physiologically relevant models has limited research in this field of poultry gut health and led to an over-reliance on the use of live birds for experiments. The development of complex 3D intestinal organoids or "mini-guts" has created ample opportunities for poultry research in this field. A major advantage of the floating chicken intestinal organoids is the combination of a complex cell system with an easily accessible apical-out orientation grown in a simple culture medium without an extracellular matrix. The objective was to investigate the impact of a commercial proprietary blend of organic acids and essential oils (OA+EO) on the innate immune responses and kinome of chicken intestinal organoids in a Salmonella challenge model. To mimic the in vivo prolonged exposure of the intestine to the product, the intestinal organoids were treated for 2 days with 0.5 or 0.25 mg/mL OA+EO and either uninfected or infected with Salmonella and bacterial load in the organoids was quantified at 3 hours post infection. The bacteria were also treated with OA+EO for 1 day prior to challenge of the organoids to mimic intestinal exposure. The treatment of the organoids with OA+EO resulted in a significant decrease in the bacterial load compared to untreated infected organoids. The expression of 88 innate immune genes was investigated using a high throughput qPCR array, measuring the expression of 88 innate immune genes. Salmonella invasion of the untreated intestinal organoids resulted in a significant increase in the expression of inflammatory cytokine and chemokines as well as genes involved in intracellular signaling. In contrast, when the organoids were treated with OA+EO and challenged with Salmonella, the inflammatory responses were significantly downregulated. The kinome array data suggested decreased phosphorylation elicited by the OA+EO with Salmonella in agreement with the gene expression data sets. This study demonstrates that the in vitro chicken intestinal organoids are a new tool to measure the effect of the feed additives in a bacterial challenge model by measuring innate immune and protein kinases responses.

Chondronecrosis with osteomyelitis in broilers: further defining a bacterial challenge model using standard litter flooring and protection with probiotics

This report demonstrates that high levels of lameness can be induced by a limited bacterial challenge in drinking water for birds raised on litter flooring, comparable with lameness induced by the gold standard for inducing lameness, growth on suspended wire flooring. The bacterium used in the challenge was cultured from lesions in birds induced for bacterial chondronecrosis with osteomyelitis (BCO) in the wire-flooring model so the epidemiology appears similar. The litter-flooring model could better approximate broiler operations. Furthermore, the work demonstrates that 2 commercial probiotics (GalliProTect and GalliProMax) can reduce lameness in the bacterial challenge litter-flooring model. Lameness attributable to BCO is one of the most significant animal welfare issues for broiler production. The wire-flooring and litter-flooring models afford alternatives for understanding the etiology, and epidemiology of BCO, and development of management strategies to reduce lameness. Probiotics afford a promising management strategy. The results suggest that the probiotic protection may extend beyond just intestinal health and intestinal barrier function.

Haptoglobin therapy has differential effects depending on severity of canine septic shock and cell-free hemoglobin level.

During sepsis, higher plasma cell-free hemoglobin (CFH) levels portend worse outcomes. In sepsis models, plasma proteins that bind CFH improve survival. In our canine antibiotic-treated Staphylococcus aureus pneumonia model, with and without red blood cell (RBC) exchange transfusion, commercial human haptoglobin (Hp) concentrates bound and compartmentalized CFH intravascularly, increased CFH clearance, and lowered iron levels, improving shock, lung injury, and survival. We now investigate in our model how very high CFH levels and treatment time affect Hp's beneficial effects. Two separate canine pneumonia sepsis Hp studies were undertaken: one with exchange transfusion of RBCs after prolonged storage to raise CFH to very high levels and another with rapidly lethal sepsis alone to shorten time to treat. All animals received continuous standard intensive care unit supportive care for 96 hours. Older RBCs markedly elevated plasma CFH levels and, when combined with Hp therapy, created supraphysiologic CFH-Hp complexes that did not increase CFH or iron clearance or improve lung injury and survival. In a rapidly lethal bacterial challenge model without RBC transfusion, Hp binding did not increase clearance of complexes or iron or show benefits seen previously in the less lethal model. High-level CFH-Hp complexes may impair clearance mechanisms and eliminate Hp's beneficial effect during sepsis. Rapidly lethal sepsis narrows the therapeutic window for CFH and iron clearance, also decreasing Hp's beneficial effects. In designing clinical trials, dosing and kinetics may be critical factors if Hp infusion is used to treat sepsis.

Study on the Efficacy of Pondguard in Improving Clinical Performance of White Leg Shrimp (Penaeus Vannamei) in an AHPND Bacterial Challenge Model

Study on the Efficacy of Pondguard in Improving Clinical Performance of White Leg Shrimp (Penaeus Vannamei) in an AHPND Bacterial Challenge Model

Chondronecrosis with osteomyelitis in broilers: Further defining a bacterial challenge model using the wire flooring model

Lameness in broiler chickens is a significant animal welfare and financial issue. Bacterial chondronecrosis with osteomyelitis (BCO) leading to lameness can be enhanced by rearing young broilers on wire flooring. Using the wire floor system, we identified Staphylococcus agnetis as the predominant isolate in BCO of the proximal tibiae and femora, and blood of lame broilers. Administration of S. agnetis isolates in water can induce lameness. We now report that the wire floor system increases bacterial translocation into the blood stream. We have also determined that approximately 105 CFU/mL is the minimum effective dose in the drinking water and that challenge at 10, 20, or 30 days of age produces similar incidences of lameness. BCO isolates of S. agnetis are much more effective than other Staphylococcus species and can overwhelm the protective effects of some commercial probiotics. Finally, we also demonstrated that the BCO lameness induced by administration of S. agnetis in the drinking water is transmissible to unchallenged broilers in the same pen.

Evidence for cyclic diguanylate as a vaccine adjuvant with novel immunostimulatory activities

Cyclic diguanylate (c-di-GMP), a bacterial signaling molecule, possesses protective immunostimulatory activity in bacterial challenge models. This study explored the potential of c-di-GMP as a vaccine adjuvant comparing it with LPS, CpG oligonucleotides, and a conventional aluminum salt based adjuvant. In this evaluation, c-di-GMP was a more potent activator of both humoral and Th1-like immune responses as evidenced by the robust IgG2a antibody response it induced in mice and the strong IFN-γ, TNF-α and IP-10 responses, it elicited in mice and in vitro in non-human primate peripheral blood mononuclear cells. Further, compared to LPS or CpG, c-di-GMP demonstrated a more pronounced ability to induce germinal center formation, a hallmark of long-term memory, in immunized mice. Together, these data add to the growing body of evidence supporting the utility of c-di-GMP as an adjuvant in vaccination for sustained and robust immune responses and provide a rationale for further evaluation in appropriate models of immunization.

A role of cellular prion protein in programming T‐cell cytokine responses in disease

The cellular prion protein (PrP(C)) is widely expressed in neural and non-neural tissues, but its function is unknown. Elucidation of the part played by PrP(C) in adaptive immunity has been a particular conundrum: increased expression of cell surface PrP(C) has been documented during T-cell activation, yet the functional significance of this activation remains unclear, with conflicting data on the effects of Prnp gene knockout on various parameters of T-cell immunity. We show here that Prnp mRNA is highly inducible within 8-24 h of T-cell activation, with surface protein levels rising from 24 h. When measured in parallel with CD69 and CD25, PrP(C) is a late activation antigen. Consistent with its up-regulation being a late activation event, PrP deletion did not alter T-cell-antigen presenting cell conjugate formation. Most important, activated PrP(0/0) T cells demonstrated much reduced induction of several T helper (Th) 1, Th2, and Th17 cytokines, whereas others, such as TNF-alpha and IL-9, were unaffected. These changes were investigated in the context of an autoimmune model and a bacterial challenge model. In experimental autoimmune encephalomyelitis, PrP-knockout mice showed enhanced disease in the face of reduced IL-17 responses. In a streptococcal sepsis model, this constrained cytokine program was associated with poorer local control of infection, although with reduced bacteremia. The findings indicate that PrP(C) is a potentially important molecule influencing T-cell activation and effector function.

Protection against an Escherichia coli-induced sepsis by alkaline phosphatase in mice.

Alkaline phosphatase (AP) is a phosphate transferase present in bacteria and eukaryotes. In previous studies, we have shown that AP is able to dephosphorylate lipopolysaccharide (LPS) at physiological pH levels. Because LPS is the causative agent of gram-negative sepsis, we hypothesize that AP might be used as a medication during early stages of LPS-induced septic shock. We have demonstrated protective effects of AP when this enzyme was administered simultaneously with LPS. However, a major question of anti-LPS therapies is whether they are also effective after systemic infiltration of whole bacteria and if they also act in later stages of the disease. To test this, we explored the protective effects of AP from human placenta (plAP) in a bacterial challenge model in Balb/c mice. AP was intravenously administered 20 min after a bacterial intraperitoneal inoculation of 2 to 5 x 10 CFU of Escherichia coli suspended in a 100-microL volume of saline. It was shown that AP attenuated the systemic host response upon E. coli. Body temperature was normalized as compared with untreated septic mice. Also, serum nitric oxide levels 24 h after the injection of bacteria were reduced almost to control levels in mice that received AP. Moreover, survival after 24 h was significantly higher in the AP-treated group compared with the nontreated control group.

Influence of a probiotic/trace mineral mixture on growth performance and Salmonella choleraesuis shedding in nursery pigs (1996)

We tested a probiotic/trace mineral mixture using a bacterial challenge model in high-health status pigs. We examined the influence of the mixture on growth performance, hematologic parameters, haptoglobin concentration, and Salmonella choleraesuis shedding in nursery pigs. A successful model of S. cholereasuis challenge was established. However, the probiotic/trace mineral mixture did not influence growth performance, bacterial shedding, or other parameters examined in this experiment.; Swine Day, Manhattan, KS, November 21, 1996