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Veterinary research2013; 44(1); 49; doi: 10.1186/1297-9716-44-49

Comparative genome sequencing identifies a prophage-associated genomic island linked to host adaptation of Lawsonia intracellularis infections.

Abstract: Lawsonia intracellularis is an obligate intracellular bacterium and the causative agent of proliferative enteropathy (PE). The disease is endemic in pigs, emerging in horses and has also been reported in a variety of other animal species, including nonhuman primates. Comparing the whole genome sequences of a homologous porcine L. intracellularis isolate cultivated for 10 and 60 passages in vitro, we identified a 18-kb prophage-associated genomic island in the passage 10 (pathogenic variant) that was lost in the passage 60 (non-pathogenic variant). This chromosomal island comprises 15 genes downstream from the prophage DLP12 integrase gene. The prevalence of this genetic element was evaluated in 12 other L. intracellularis isolates and in 53 infected animals and was found to be conserved in all porcine isolates cultivated for up to 20 passages and was lost in isolates cultivated for more than 40 passages. Furthermore, the prophage region was also present in 26 fecal samples derived from pigs clinically affected with both acute and chronic forms of the disease. Nevertheless, equine L. intracellularis isolates evaluated did not harbor this genomic island regardless of the passage in vitro. Additionally, fecal samples from 21 clinically affected horses and four wild rabbits trapped in horse farms experiencing PE outbreaks did not show this prophage-associated island. Although the presence of this prophage-associated island was not essential for a virulent L. intracellularis phenotype, this genetic element was porcine isolate-specific and potentially contributed to the ecological specialization of this organism for the swine host.
Publication Date: 2013-07-04 PubMed ID: 23826661PubMed Central: PMC3716683DOI: 10.1186/1297-9716-44-49Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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This research identifies a specific genetic element linked to the host adaptation of Lawsonia intracellularis, a bacterium that causes intestinal disease in animals, particularly pigs. The 18-kb prophage-associated genomic island, as it is termed, was found to be conserved in pig isolates of the bacterium, but absent in isolates from other species such as horses.

Context and Objective

  • The study examines Lawsonia intracellularis, a bacterium causing proliferative enteropathy, an endemic intestinal disease in pigs that has also been reported in other animals.
  • The goal was to understand the microbial mechanism behind host adaptation, particularly in pigs, by comparing the whole genome sequences of the bacterium from different stages of cultivation and isolates from various species.
  • Methods

    • The researchers compared two versions of the bacterium: a pathogenic variant (cultivated for 10 passages) and a non-pathogenic variant (cultivated for 60 passages).
    • A genomic element referred to as an 18-kb prophage-associated genomic island was identified in the pathogenic variant but had disappeared in the non-pathogenic variant.
    • The team then evaluated the prevalence of this genomic island in 12 other L. intracellularis isolates along with samples from 53 infected animals.
    • Findings

      • The prophage-associated genomic island was found in all pig isolates cultivated for up to 20 passages, but was lost after more than 40 passages.
      • This genetic element was also present in samples taken from pigs clinically affected with both acute and chronic forms of the disease.
      • However, the genomic island was not found in horse isolates of the bacterium, or in fecal samples from horses or wild rabbits affected by the disease.

      Implications

      • The absence of the 18-kb prophage-associated genomic island in non-porcine isolates and its conservation during early passages for pig isolates suggest that this genetic element is specific to the pig host.
      • While the genomic island is not essential for the pathogenicity of L. intracellularis, it could contribute to the bacterium’s adaptation and ecological specialization within the swine host.
      • This discovery has potential impacts on disease control strategies and medical intervention in managing proliferative enteropathy in pigs and other animals.

Cite This Article

APA
Vannucci FA, Kelley MR, Gebhart CJ. (2013). Comparative genome sequencing identifies a prophage-associated genomic island linked to host adaptation of Lawsonia intracellularis infections. Vet Res, 44(1), 49. https://doi.org/10.1186/1297-9716-44-49

Publication

ISSN: 1297-9716
NlmUniqueID: 9309551
Country: England
Language: English
Volume: 44
Issue: 1
Pages: 49

Researcher Affiliations

Vannucci, Fabio A
  • Department of Veterinary and Biomedical Science, College of Veterinary Medicine, University of Minnesota, St, Paul, MN, USA. vannu008@umn.edu.
Kelley, Molly R
    Gebhart, Connie J

      MeSH Terms

      • Animals
      • Desulfovibrionaceae Infections / microbiology
      • Desulfovibrionaceae Infections / veterinary
      • Feces / microbiology
      • Genomic Islands
      • High-Throughput Nucleotide Sequencing / veterinary
      • Horse Diseases / microbiology
      • Horses
      • Intestinal Diseases / microbiology
      • Intestinal Diseases / veterinary
      • Lawsonia Bacteria / genetics
      • Lawsonia Bacteria / pathogenicity
      • Lawsonia Bacteria / physiology
      • Polymerase Chain Reaction / veterinary
      • Prophages / genetics
      • Swine
      • Swine Diseases / microbiology
      • Virulence

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