Keywords

1. Cross-protection vaccine
2. Poultry Salmonella outbreak
3. Food safety
4. Vaccine for turkeys
5. Antibiotic-resistant Salmonella

In a significant advancement for the poultry industry and food safety, a recently published study in the journal ‘Vaccine’ demonstrates that a commercial vaccine can provide cross-protection against the notorious foodborne pathogens Salmonella enterica serovars Infantis and Hadar in turkeys. The research, authored by Shawn Bearson et al. from the United States Department of Agriculture (USDA) and appearing under DOI 10.1016/j.vaccine.2023.12.054, assesses the effectiveness of a live, attenuated Salmonella Typhimurium vaccine in limiting the colonization of these harmful bacteria in turkeys, which could have major implications for public health.

Human foodborne outbreaks caused by antibiotic-resistant Salmonella enterica have become a worrisome public health concern. These outbreaks are often linked to contaminated poultry products and involve serogroup C serovars, particularly Infantis and Hadar. The health risks posed by these pathogens, combined with their resistance to conventional antibiotic treatments, necessitate the development of effective control strategies.

In response to the rising challenge posed by these Salmonella serovars, the Bearson-led research team embarked on evaluating a commercially available Salmonella vaccine specifically designed for turkeys. Traditionally, vaccines target the serovar of Salmonella most relevant to the species they’re administered to. However, this study explored the novel concept of cross-protection, wherein a vaccine developed for Salmonella serogroup B (Typhimurium) was used against serogroup C serovars (Infantis and Hadar).

Their experimental design included the inoculation of turkeys with the serogroup B S. Typhimurium vaccine. Subsequently, these vaccinated birds, as well as a non-vaccinated control group, were challenged with the serogroup C S. Infantis and S. Hadar strains. Researchers sought to assess the vaccine’s efficacy by observing colonization levels in various intestinal tissues such as the cecum, cecal tonsils, and cloaca, along with systemic dissemination to organs like the spleen and bone marrow.

The results were cause for optimism. Vaccination significantly reduced the intestinal colonization by S. Infantis and S. Hadar. Moreover, the vaccine seemed to play a crucial role in limiting the systemic spread of these pathogens, as evidenced by the lower bacterial counts in the spleens of vaccinated birds. While non-vaccinated turkeys displayed S. Infantis dissemination into the bone marrow, vaccinated groups showed no such spread. Remarkably, S. Hadar did not seem to reach the bone marrow in either group, indicating differing pathogenic behaviors between the two serovars.

An important aspect of the study was the focus on the pESI megaplasmid found within the S. Infantis challenge strain. This particular plasmid is believed to harbor virulence mechanisms that facilitate the bacterium’s ability to colonize and systemically spread within the host. The evidence suggests that the vaccine’s efficacy extends to countering the pESI plasmid’s contributory role in pathogenesis

The successful demonstration of cross-protection implies that it may be possible to effectively use a single vaccine to safeguard against multiple Salmonella serovars in turkeys. This finding represents a potentially transformative development for poultry disease management, enhancing the safety of poultry products that reach consumer markets. It could lead to a reduction in foodborne outbreaks and contribute to more sustainable farming practices by decreasing reliance on antibiotics, which are becoming less effective due to rising resistance in bacterial populations.

References

1. Bearson, Shawn M. D., et al. “Commercial vaccine provides cross-protection by reducing colonization of Salmonella enterica serovars Infantis and Hadar in turkeys.” Vaccine (2023): DOI: 10.1016/j.vaccine.2023.12.054.
2. USDA, ARS, National Animal Disease Center, Food Safety and Enteric Pathogens Research Unit. (n.d.).
3. Angus, Wilson. “Salmonella and Eggs: From Production to Plate.” International Journal of Food Microbiology (2019).
4. FDA. “National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS): Human Isolates Final Report” (2022).
5. CDC. “Antibiotic Resistance Threats in the United States.” (2019).

Declaration of Competing Interest

The authors of the study, Shawn Bearson and colleagues, have declared that this research was financially supported by the USDA Food Safety and Inspection Service.

In summary, the research conducted by Bearson et al. points to a future where commercial vaccines could play an essential role in preventing the spread of multiple Salmonella serovars in poultry production. The broader implications for public health, the poultry industry, and the environment make this an exciting development in the ongoing battle against foodborne diseases and antibiotic resistance. As the study continues to be evaluated and peer-reviewed, the hope is that the findings will lead to improved strategies for controlling Salmonella infections in turkeys and over time, higher food safety standards globally.