Abstract

Background:
Salmonella infection is one of the main zoonotic diseases threatening poultry and food safety. Various serovars, including Salmonella enteritidis, S. typhimurium, S. kentucky, and S. gallinarum, cause economic losses and public health risks. The rise of multidrug-resistant (MDR) Salmonella underscores the need for vaccination.

Aim:
This study assessed the safety and effectiveness of a tetravalent inactivated Salmonella vaccine (POULMMUNE™ SALMONELLA BCD) in reducing fecal shedding and systemic invasion in chickens.

Methods:
Antimicrobial susceptibility was tested for Salmonella strains isolated from poultry. The vaccine, expressed as a water-in-oil emulsion with Montanide™ ISA 70 VG, was administered to 250 SPF White Leghorn chickens, which were divided into vaccinated and control groups. Safety was assessed through clinical monitoring, while efficacy was evaluated by serological responses, fecal shedding, and post-challenge bacterial translocation to the liver. The most probable number (MPN) method was used to determine bacterial counts, and statistical analysis was performed (p < 0.05).

Results:
MDR was detected in all isolates, with high resistance to clindamycin, penicillin, ampicillin, tetracycline, and streptomycin. The vaccine was well tolerated with no adverse effects. Vaccinated birds had significantly higher antibody titers, reduced fecal shedding by 14 days post-challenge, and lower liver translocation, with no detectable bacteria by direct plating from day 4 post-challenge.

Conclusion:
The vaccine demonstrated strong safety, immunogenicity, and efficacy in reducing shedding and systemic dissemination of Salmonella. Given the high prevalence of MDR Salmonella, vaccination is crucial for controlling infection and minimizing antibiotic reliance in poultry. Further studies should be conducted to optimize formulations and assess field efficacy.

Key words: Salmonella; Tetravalent vaccine; Antimicrobial resistance; Bacterial translocation; Food safety.