Airborne challenge of chickens vaccinated orally with the genetically-defined Salmonella enteritidis aroA strain CVL30

Evaluation of 3-week-old layer chicks intratracheally challenged with Salmonella isolates from serogroup c1 (O:6,7) and Salmonella Enteritidis

With the exception to Salmonella enterica serotype Typhimurium and S. Enteritidis (serogroups B [O:4] and D [O:9], respectively), there have been very few studies conducted on the respiratory tract as route of infection in chickens with salmonellas from serogroup C1 (O:6,7). Therefore, the purpose of this present study was to determine the potential organ invasion by Salmonella enterica serotype Potsdam (SP), S. Mbandaka (SM), and S. Infantis (SI) from serogroup C1 (O:6,7) and compare their characteristics with those of S. Enteritidis (SE) on intratracheally (IT) challenged 3-week-old layer chicks. A total of 360 one-day-old White Leghorn layer chicks were acquired from a commercial hatchery and randomly assigned into four treatment groups (SP, SM, SI, and SE, respectively), consisting of three independent trials. Chicks were grown up to 21 days (3 weeks) and IT-challenged thereafter with 10⁶ CFU of respective salmonella organisms per group (n = 30). Chicks (n = 5) were humanely sacrificed every 24 h for 6 days post-IT infection and organs such as lung, heart, liver, spleen, kidney and caecal content were cultured for salmonella. All treatment groups exhibited colonization of lungs and caecal contents at 1 d (P = 0.475) and 4 d (P = 0.696) post-IT infection, respectively. There was no isolation of SP, SM, and SI in heart, liver, spleen, and kidney. In contrast, SE was obtained from heart, liver, and spleen of IT-infected chicks. The findings of this study contribute to a better understanding of the importance of the respiratory route in salmonella infection in poultry.

Protective immunity of biodegradable nanoparticle-based vaccine against an experimental challenge with Salmonella Enteritidis in mice

Salmonella spp. infections transmitted by contaminated poultry and eggs represent a major global health burden. Salmonella enterica serovar. Enteritidis is the leading cause of human salmonellosis worldwide. The cell surface antigens of Salmonella Enteritidis play an important role in the host-pathogen interactions and as such represent potential candidates for subunit-vaccine development. An immunogenic subcellular extract obtained from whole Salmonella Enteritidis cells (HE) was encapsulated in nanoparticles made with the polymer Gantrez (HE-NP). Proteomics was used to investigate the complex protein nature of the HE extract. Immunogenicity and protection studies against lethal Salmonella Enteritidis challenge were performed in BALB/c mice. Increased survival was observed in vaccinated mice as compared to a control group; 80% of the mice immunized with the HE-NP formulation survived even when administered 49 days before the lethal challenge. The cytokines released from in vitro-stimulated spleens showed a strong gamma interferon response in all immunized groups at day 10 post-immunization. However, the immunity induced by HE-NP at day 49 post-immunization suggests the involvement of a TH2 subclass in the protective effect. The potential for mucosal vaccination suggests that HE-nanoparticles may represent an important alternative to the conventional attenuated vaccines against Salmonella Enteritidis.

Development of a lavage procedure to collect lung secretions from chickens for evaluating respiratory humoral immunity

Mucosal immunology research has been hampered by the difficulty and labour-intensiveness of collecting samples. This is especially true for sites such as the lung, and the present paper describes a simple method for obtaining samples from this organ in chickens. Following sacrifice, the bird was placed on its back and the trachea was cut and exteriorized. Narrow-diameter tubing, to which a 30 ml syringe was attached, was threaded down the trachea to the bronchi and air was evacuated from the lung. Warm buffer was administered and the lung sample then aspirated, processed and frozen. In the current experiment this sampling system was tested on hens that were challenged with Salmonella Enteritidis. Elevated anti-Salmonella Enteritidis antibody levels in lung from infected hens were observed in significantly more infected hens than non-infected control hens in two trials. The simplicity and utility of this sampling system will make it a useful tool for those laboratories wishing to expand their humoral mucosal immunology capabilities, even for study of non-respiratory pathogens.

Evaluation of 12 stabilizers in a developed attenuated Salmonella Enteritidis vaccine

The development of a stable live attenuated Salmonella Enteritidis (SE) vaccine, resisting heat stress during transportation and storage in unequipped tropical and subtropical zones of the world, is highly recommended. Twelve stabilizers were individually supplemented into a 9 ml volume of sterile distilled water resulting in concentrations of 1, 2, 3, 4 and 5%. A volume of 1 ml of attenuated live SE vaccine is added over the 9 ml of each concentration of the stabilizers. The differently stabilized SE vaccines were stressed at 55 degrees C for 48 h. The lowest percent reductions in SE cell viability by specified level of each stabilizer in ascending order were: 22.3% by 2% skim milk, 55.1% by 5% bovine serum albumin (BSA), 59.2% by 4% sorbitol, 74.4% by 3% maltose, 75% by 2% honey, 91.3% by 3% histidine, 96.9% by 1% heparin, 97.5% by 4% dextrose, 97.9% by 5% lactose, 99.4% by 5% sucrose, 99.5% by 2% gelatin, and 100% by 1-5% glycerol. In narrowing the concentration levels of skim milk to include 1.00, 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, 2.75, and 3.00%, the 2.50% was the optimum level resulting in minimal percent reduction in SE cell viability of 18.9% after exposure to the defined heat stress.