Vaccination Against Lawsonia intracellularis Decreases Shedding of Salmonella enterica serovar Typhimurium in Co-Infected Pigs and Alters the Gut Microbiome

Abstract

Salmonella enterica serovar Typhimurium continues to be a major cause of foodborne illness worldwide and pork can serve as a source of infection. Co-infection of S. enterica with Lawsonia intracellularis, a common intestinal pathogen of swine, has been found as risk factor for increased S. enterica shedding. The objective of this study was to investigate if vaccination against L. intracellularis could lead to decreased S. Typhimurium shedding. To test this hypothesis, pigs were challenged with either S. Typhimurium or S. Typhimurium and L. intracellularis, with and without L. intracellularis vaccination (n = 9 per group). A non-challenged group served as a negative control. Vaccination decreased the shedding of S. Typhimurium in co-infected animals by 2.12 log10 organisms per gram of feces at 7 days post infection. Analysis of the microbiome showed that vaccination led to changes in the abundance of Clostridium species, including Clostridium butyricum, in addition to other compositional changes that may explain the protection mediated against S. Typhimurium. These results indicate that vaccination against L. intracellularis in co-infected herds may provide a new tool to increase food safety by helping to prevent S. enterica without the need for antibiotics.

Lawsonia intracellularis: Revisiting the Disease Ecology and Control of This Fastidious Pathogen in Pigs

“…It is now acknowledged that L. intracellularis infection is common in weaned pigs ( 2 ). It is also known that L. intracellularis infection leads to changes in the pig gut microbiome, indicating a complex association ( 70 , 90 , 91 ). Early studies show that experimental infection of pigs with a cell culture propagated pure L. intracellularis inoculum does not cause disease in gnotobiotic pigs but the same inoculum produces disease in conventional pigs ( 12 ).…”

Spread of an Experimental Salmonella Derby Infection in Antibiotic-Treated or Lawsonia intracellularis Vaccinated Piglets

“…However, it cannot be ruled out that the vaccination itself has a protective effect. Vaccination against L. intracellularis at three weeks of age significantly reduced S. Typhimurium shedding ( p < 0.05) in co-infected animals in comparison to the co-infected group without vaccination and the group challenged with S. Typhimurium alone [ 41 ]. Twenty-one days post vaccination, the animals were challenged with a pure culture of L. intracellularis (2 × 10 9 organisms per pig; strain PHE/MN1-00).…”

“…Twenty-one days post vaccination, the animals were challenged with a pure culture of L. intracellularis (2 × 10 9 organisms per pig; strain PHE/MN1-00). One week post- L. intracellularis challenge, the pigs were challenged orally with S. Typhimurium (strain 798; 1 × 10 8 organisms per pig) [ 41 ]. At seven days post-infection, the co-challenged non-vaccinated group shed 2.94 log 10 S. Typhimurium organisms per gramme faeces, while the vaccinated co-challenged group shed 0.82 log 10 S. Typhimurium organisms per gramme faeces ( p = 0.003) [ 41 ].…”

“…One week post- L. intracellularis challenge, the pigs were challenged orally with S. Typhimurium (strain 798; 1 × 10 8 organisms per pig) [ 41 ]. At seven days post-infection, the co-challenged non-vaccinated group shed 2.94 log 10 S. Typhimurium organisms per gramme faeces, while the vaccinated co-challenged group shed 0.82 log 10 S. Typhimurium organisms per gramme faeces ( p = 0.003) [ 41 ]. These results indicate that the vaccination against L. intracellularis impacts the microbiome and reduces shedding of S. Typhimurium in co-infected animals [ 41 ].…”

Potent O-antigen-deficient (rough) mutants of Salmonella Typhimurium secreting Lawsonia intracellularis antigens enhance immunogenicity and provide single-immunization protection against proliferative enteropathy and salmonellosis in a murine model

“…Previous studies have revealed that LI infection is a risk factor for fecal shedding of Salmonella Typhimurium (ST) in affected pigs [ 4 ]. It has been reported that colonization and shedding of ST significantly increased in pigs experimentally co-infected with LI and ST [ 5 ]. This supports the hypothesis that both pathogens have indirect interactions that might be mediated by pre-disposing organisms, resulting in underlying changes in the composition of the intestinal microbiome [ 6 ].…”