2020-21 Rapid Ag: Not All Salmonella Are Created Equal: A Comprehensive Study to Determine the Efficacy of Alternative Interventions to Control Emerging Salmonella Serovars of Food Safety Importance in Turkey Production and Processing
Anup Kollanoor Johny
Salmonella is a leading cause of foodborne illness. Contaminated turkey products are sources for Salmonella to humans. Various Salmonella (serovars), common and emerging, are encountered in the turkey production and processing environments. Due to multiple sources of Salmonella on farms, and many serotypes harboring turkeys, it is difficult to control the pathogen with a single approach. Recent outbreak of Salmonella Reading, a very rare serotype causing outbreaks, through turkey products, is alarming as an emerging Salmonella.
Salmonella outbreaks from turkeys is a high priority problem for Minnesota’s industry: Minnesota ranks no. 1 in the number of turkeys raised in the USA. Contamination of turkey products with Salmonella has historically resulted in product recalls causing enormous losses to the industry. Turkey burgers, ground turkey, and raw turkey products have been implicated in multistate outbreaks caused by S. Hadar (2011), S. Heidelberg (2011), and S. Reading (2018), respectively2,3,4. Attesting to this problem, the August 2018 USDA report on the aggregate Salmonella categorization of poultry establishments revealed that 50% of processing plants exceeded the maximum allowable positive tests for turkey comminuted products14. Salmonella colonizes all segments of the turkey gastrointestinal tract (GIT), including 2 crop, and most importantly the ceca, two sac-like structures located between small and large intestines. A faulty processing step could result in contamination of carcasses resulting in cross-contamination11,25. These situations warrant the Minnesota’s turkey industry to fortify Salmonella control efforts in both production and processing. Emerging Salmonellas aggravate the problem: In addition to the major serovars that cause human infections (S. Typhimurium, S. Heidelberg)11, an increased prevalence of fairly uncommon serovars in turkeys13 has raised concerns, warranting acceleration of research to find rapid solutions and education efforts. For example, the recent S. Reading outbreak through raw turkey products has brought this serovar into light as an emerging issue4. Although S. Reading has been rarely associated with foodborne outbreaks, thus far, it has resulted in 90 illnesses from 26 states since outbreak started in 2018 July4. This serovar was among the top 10 in turkeys until 2014, rising to the top 3 list since 2014, resulting in a foodborne outbreak in 201813. This pattern follows S. Heidelberg and S. Hadar, other major serovars in turkey production. In addition, a careful focus has to be given to other serotypes, including S. Agona and S. Saintpaul since they are also frequently isolated from turkeys4,11,12,13. S. Agona has been a constant presence in the turkey carcasses and ground turkey in the U.S.13, contributing 5,072 laboratory confirmed illnesses in 2014. Another emerging serovar, S. Saintpaul, was among the top 3 during 2005 and 2009, and consistently isolated in the past 15 years13.
Proposed solution to the problem: Probiotics and vaccination for production, and essential oils for processing: Probiotics are beneficial organisms that enhance immune response, nutrient absorption, and control of pathogens17. Historically, vaccination is a major control method against Salmonella on farms although variations in efficacy exist7,10. Essential oils (EOs) are emerging alternatives due to their rapid antibacterial property28. Due to many sources of Salmonella on farms, and various serovars harboring turkeys, no single approach may effectively eliminate the pathogen. It is likely that combined strategies could control Salmonella in turkeys more effectively, and our ongoing research results (2014 – 2018) at UMN supports such an approach23. The uniqueness of our approach is: A) We propose alternative combinations: The direct basis for this proposal is the discovery that the combination of PF and VC (AviPro® Megan® Egg - a killed S. Typhimurium vaccine) reduced S. Heidelberg to non-detectable levels in the cecum, liver, and spleen of growing turkeys23. We rationalize that this magnitude of reduction with S. Heidelberg (a common turkey serovar) could be expanded to the emerging serovars, S. Reading, S. Agona, and S. Saintpaul in market-age turkeys. However, this needs comprehensive testing since all Salmonellae are not created equal1. B) We target multiple Salmonella serovars with the combinations: Strategies to focus on a particular serovar may not be ideal due to multiple serovars present in a flock at a time. Serovars with a historically lesser significance have been increasingly colonizing turkeys as current interventions are geared towards controlling the major serovars. With the measures to control S. Enteritidis and S. Typhimurium, serotypes such as S. Heidelberg, S. Reading, S. Saintpaul, and S. Agona have emerged in turkeys4,11,13, necessitating broadening the control approaches to include multiple serovars. C) We propose combinations to potentiate host-gut-defense against Salmonella and directly target the pathogen: Once ingested, Salmonella traverses through GIT to colonize cecum, employing genetic mechanisms, most importantly, flagellar motility [motA, motB (torque and rotation), flhD (regulation) fliC (biosynthesis)]19. The host responds by releasing β defensins 4 and 9 (gal4, gal9) to exclude Salmonella at the gut level24. Salmonella competes with the indigenous gut microbiota for attachment to the intestinal cells and colonize [hilA (regulator), hilC (activator)]19. Once attached, Salmonella expresses invasion (hilA, hilC), a process that causes inflammation [releasing interleukins (IL)- 1β, IL-6, IL-8] and host immune response (via immunoglobulins, IgA, IgG, IgM)15. In addition, Salmonella utilizes ttrS (tetrathionate reduction), eutE (ethanolamine utilization), pduA (propanediol utilization) genes for anaerobic survival19. Although other mechanisms are involved, characterized and most critical genes at the host-Salmonella interface are targeted. We rationalize that while vaccination protects the host by generating secretory antibodies (IgA) against the imminent attack of the pathogen, probiotics enhance vaccine efficacy by restoring gut microbiota, upregulate β defensins, reduce proinflammatory cytokines, and directly target Salmonella virulence. Moreover, Salmonella can attach to the carcass skin during processing by adhesion. EOs may down-regulate key genes for adhesion (flgA, flgC, flgK)26 reducing pathogen attachment to skin, and inactivating them in chilling waters preventing cross-contamination.
Short and Long-Range Cost Benefit Potential: The combination of alternatives would result in greater reduction of Salmonella in market-age turkeys and ground turkey, a finding directly applicable to the industry. The microbiome analysis would identify unique group of bacteria playing significant role in Salmonella reduction. Also, regulation of key host and pathogen genes in response to alternative interventions is expected, a finding with significant value to develop farm-side or processing-line specific markers for industry. We will use the data to submit larger multistate federal grants.
Project Goals and Objectives
Our recent research at UMN indicates that combining a GRAS-status dairy probiotic strain, Propionibacterium freudenreichii subsp. freudenreichii (PF) and a Salmonella Typhimurium vaccine (SV) yielded a complete reduction of S. Heidelberg, a major Salmonella serovar, in growing turkeys 23,24. Also, in another study, we found that Lemongrass essential oil (LGEO) and Pimenta essential oil (PEO) completely inactivated S. Heidelberg from scalding and chilling waters 8,9,22. Hypothesis: The combination of PF and SV will result in reduction of multiple Salmonella serotypes in market-age turkey hens. LGEO and PEO will inactivate Salmonella in ground turkey without adversely affecting sensory attributes. Our outreach will result in improved knowledge on alternative interventions for producers, processors, and consumers.
- Preharvest: To determine the efficacy of PF and SV in combination in market-age turkey hens, against Salmonella serovars (1) S. Reading, (2) S. Agona and (3) S. Saintpaul.
- Postharvest: To determine the efficacy of PEO and LGEO as post-chill antimicrobials on reduction of Salmonella, spoilage bacteria and sensory attributes of ground turkey
- Extension: To disseminate project results to turkey growers, processors, and consumers.
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