Poultry production has become the fastest-growing sector in global meat supply. However, the intensification of poultry farming has increased the risk of zoonotic transmission of bacterial pathogens such as Salmonella spp., Campylobacter spp., Escherichia coli, Clostridium perfringens, and Listeria monocytogenes. These bacterial agents pose major public health concerns, contributing to millions of human infections annually and substantial economic losses. Historically, antibiotic growth promoters (AGPs) were widely used to mitigate disease burden and improve poultry productivity. Yet, the global shift away from AGPs due to concerns over antimicrobial resistance has spurred interest in antimicrobial alternatives. Among these, probiotics have been explored as a promising preharvest intervention. This review investigates major bacterial foodborne pathogens associated with poultry and evaluates the practical implementation of probiotic-based strategies in modern poultry production systems, with the goal of reducing pathogen load and enhancing overall food safety.

This study was undertaken to evaluate and compare the efficacy of different multi-antigen vaccines, including heat-inactivated, whole lysate, and subunit (outer membrane proteins [OMPs]) C. jejuni vaccines along with the immunostimulant CpG ODN in controlling Campylobacter colonization in chickens. In the first trial, 125 μg of C. jejuni OMPs and 50 μg of CpG ODN were administered individually or in combination, either in ovo to chick embryos or subcutaneously (SC) to one-day-old chicks. In the second trial, different concentrations of C. jejuni antigens (heat-killed, whole lysate, and OMPs) were administered SC to one-day-old chicks. The results of the first trial revealed that SC immunization with the combination of CpG ODN and C. jejuni OMPs elevated interferon (IFN)-γ, interleukin (IL)-1β, and IL-13 gene expression in the spleen, significantly increased serum IgM and IgY antibody levels, and reduced cecal C. jejuni counts by approximately 1.2 log₁₀. In contrast, in ovo immunization did not elicit immune responses or confer protection against Campylobacter. The results of the second trial showed that SC immunization with C. jejuni whole lysate or 200 μg OMPs reduced C. jejuni counts by approximately 1.4 and 1.1 log₁₀, respectively. In conclusion, C. jejuni lysate and OMPs are promising vaccine antigens for reducing Campylobacter colonization in chickens.

Campylobacter jejuni is the leading cause of bacterial gastroenteritis worldwide, with an estimated 1.5 million human infections occurring annually in the United States alone. With chickens being considered the primary reservoir and source of infection in humans, developing effective vaccination strategies is crucial for preventing Campylobacter transmission to humans. This study aimed to examine the immunogenicity and protective efficacy of a multi-antigen subunit vaccine, consisting of C. jejuni outer membrane proteins (OMPs) and cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG ODN), in layer breeders and its potential to enhance the levels of C. jejuni-specific maternal antibodies in their offspring. Four groups of layer breeders were subcutaneously vaccinated with 200 μg C. jejuni OMPs and 50 μg CpG-ODN, individually or combined, or with PBS as a negative control. C. jejuni shedding and antibody levels were monitored in breeders for up to ten weeks post-vaccination. At the peak of antibody levels (the fourth week post-primary vaccination), fertilized eggs were collected and incubated in a sensitized egg incubator until hatching. Maternally derived antibodies (MDA) were measured in the serum of hatched chicks for five weeks post-hatch. The results revealed that breeders vaccinated with the combination of C. jejuni OMPs and CpG ODN exhibited a significant reduction in C. jejuni shedding by up to 1.37 log₁₀. This group also showed significantly higher serum and egg yolk IgY and IgM levels compared to the non-vaccinated negative control group, and notably, their chicks maintained significantly higher serum IgY, IgM, and IgA levels for five weeks post-hatch compared to the negative control group. Overall, these outcomes suggest that a combination of C. jejuni OMPs and CpG ODN could offer a promising vaccine strategy to reduce Campylobacter colonization in breeders and to boost and sustain high levels of C. jejuni-specific MDA in hatched chicks. Further research is needed to evaluate the protective effects of vaccine-associated MDA against Campylobacter infection in a commercial broiler model.

1. One hundred- and fifty-day-old chicks were divided into three groups of 50 birds (G1-G3); G1 and G2 were orally inoculated at one day old with 0.5 ml of 10⁷ TCID50/ml FAdV-D serotype 2 (MT386509.1) and FAdV-E serotype 8a (MW847902), respectively and G3 was blank control group.2. Cell-mediated immune response was evaluated by detection of CD4, CD8 T lymphocytes and the mRNA expression of IL6 and IL8 in the chicken spleen by q PCR. Additionally, immunopathology was performed at 3, 5 and 7 day post infection (dpi) and weekly until the end of the experiment.3. Results revealed that transcription of inflammatory cytokines (IL6, IL8) was up regulated in the spleen of FAdV type D and type E infected chickens at various time points relative to the control group. A marked decrease in the number of CD4 and CD8 T lymphocytes at 5 and 7 dpi in G1 of chicken infected with FAdV type D. Whereas, chickens infected with FAdV type E, the CD4 and CD8 T lymphocytes were markedly decreased at 7 dpi.4. In contrast, there were no significant differences in humoral immune responses against NDV vaccine in (G1 and G2) at different intervals post-vaccination compared to the control group. The histopathology of the bursa, thymus, and spleen in the infected groups showed lymphocytolysis with severe reticular cells hyperplasia and lymphoid depletion.5. In conclusion, fowl adenovirus types D and E have an immunosuppressive effect in broilers which may be considered one of the main causes of the continuous co-infections with other viruses reported in the field during the last 10 years.

Background/Objectives: Our recent study demonstrated that vaccination of layer breeders with Campylobacter jejuni outer membrane proteins (OMPs) and CpG ODN increased serum IgY levels and enhanced maternal antibody transfer to their offspring. However, it remained unclear which specific proteins within the OMP fraction were responsible for these effects. Methods: In this study, Western blotting (WB) and ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) were used to identify proteins associated with elevated antibody responses. Results: Among the identified proteins, seven were found in high abundance and showed strong reactivity with both hen and offspring sera. These proteins included major outer membrane protein (MOMP), fibronectin type III domain protein (FlpA), type IV secretion system protein (VirB10), capsular polysaccharide ABC transporter (KpsD), flagellin (FlaA), flagellar hook protein (FlgE), and flagellar hook-associated protein (FliD). Conclusion: Several immunoreactive candidate proteins were identified in this study; however, further validation via recombinant expression is required to evaluate their potential as vaccine candidates against C. jejuni in chickens.

Interactions between Campylobacter jejuni and host immune cells have been studied using various single-cell line models, such as macrophages and intestinal epithelial cells; however, these single-cell approaches do not fully capture the complexity of the host response. Investigating the interactions between these cell types offers a more comprehensive model for understanding Campylobacter–host dynamics. Therefore, this study aimed to investigate these interactions, specifically between intestinal epithelial cells and macrophages, using an in vitro model of C. jejuni infection. We examined whether soluble factors secreted from C. jejuni-infected HT-29 cells (human colorectal adenocarcinoma cells that express characteristics of mature intestinal cells) at 10 and 50 multiplicities of infection (MOI) influence RAW 264.7 macrophage activity, including nitric oxide (NO) production, migration, phagocytosis, bacterial killing, and the expression of cytokines (IL-6, IL-1β, TNF-α) and the chemokine CCL2. C. jejuni infection of HT-29 cells at 10 MOI induced significant IFN-γ production, a key macrophage activator. The treatment of macrophages with supernatants from HT-29 cells infected with C. jejuni significantly increased NO production, enhanced migration and phagocytic activity, and increased IL-6, TNF-α and CCL2 gene expression. However, no significant killing of phagocytosed C. jejuni was observed. On the other hand, supernatants from HT-29 cells infected with 50 MOI of C. jejuni suppressed NO production and macrophage phagocytosis, which may explain individual variations in the immune system’s ability to contain infection, potentially influenced by the infectious dose. These findings support the notion that Campylobacter can evade macrophage killing even under activated conditions. Further studies are needed to elucidate the molecular mechanisms by which Campylobacter survives within activated macrophages.