A Microbial Biorealm page on the genus Lawsonia intracellularis
Higher order taxa
Bacteria; Proteobacteria; Deltaproteobacteria; Desulfovibrionales; Desulfovibrionaceae; Lawsonia.
Genus species: Lawsonia intracellularis
Description and significance
Lawsonia intracellularis is a bacterial pathogen which causes disease in a wide range of animals, mainly pigs. The bacterial pathogen invades the intestinal epithelial cells which causes hyperplasia of the infected cells and leads to the process of disease pathogenesis. Lawsonia intracelluaris is an intracellular enterophathogen that is the cause of intestinal hyperplasia which is an abnormal increase in the number of cells in an organ or a tissue with consequent enlargement (2). "The disease has two clinical manifestations in pigs: an acute hemorrhagic form often called porcine hemorrhagic enteropathy, and a more chronic proliferative form often referred as porcine intestinal adenomatosis" (3). Lawsonia intracellularis though primarily recognized in pigs, is spreading to a wide range of mammals. Based on 16SrRNA gene sequence, Lawsonia intracellularis is related to Desulfovibio, a sulfate-reducing bacteria and Bilophila wadsworthia.
Lawsonia intracellularis has a circular chromosome and of 1,457,619 nucleotides. The genomic content includes 1,719,014 nucleotides. It had 1,337 protein genes and 49 RNA genes.
Cell structure and metabolism
The structure of Lawsonia intracellularis reveals non-spore-forming curved rods. It contains gram-negative cells that are able to retain carbol-fushsin when stained using the Ziehl-Neelsen method. It is non-pigmented and non-flagellated. Through the Ziehl-Neelsen method the cell wall of a gram-negative is shown as well as the protoplasmic structure of a prokaryote. The cells replicate within pig epithelial cell cytoplasm and are not enclosed by membrane-bound vacuoles(1).
Natural infection has not been detected in either wild or laboratory mice. However, lab mice studies represent a potential reservoir, therefore studies have further implications for the ecology and epidemiology of proliferative enteropathy, also referred to as proliferative ileitis, which is caused by infection with Lawsonia intracellularis, particularly in pigs. Though the major animal that is most susceptible are pigs, Lawsonia intracellularis has been detected laboratory animals such as "primates pig, horse, dog, rat, guinea pig, rabbit and hamster" (2). Though there is evidence of infection in primates, there is currently no direct evidence that Lawsonia intracellularis can infect humans.
An important pathway of transmission of Lawsonia intracellularis is environmental contamination with feces that are from infected animals. The period of time that Lawsonia intracellularis can remain infectious outside of the infected animal is not certain.
Lawsonia intracellularis is an intracellular bacterial pathogen which cause intestinal hyperplasia in a wide range of mammalian and avian species. As the bacteria is ingested it is able to "infect intestinal proliferating crypt epithelial cells and multiply within the apical cytoplasm" (2).
Application to Biotechnology
Information not found.
"Single-chain antibodies (scFv) exhibiting specific binding to Lawsonia intracellularis were isolated from a phagemid library expressing scFvs molecules on the surface of filamentous bacteriophages. For scFv selection whole bacterial cells were used and individual clones were tested in ELISA test. The total of seven unique clones with different fingerprint profiles was isolated. All clones were able to bind specifically in immunofluorescence assay. This is the first report of species specific recombinant antibodies against L. intracellularis".
"An in situ hybridization (ISH) procedure with a digoxigenin-labeled oligonucleotide probe for detection of Lawsonia intracellularis in paraffin-embedded tissue is described. This technique recognized 71% of PCR-positive cases and was thus superior to Warthin-Starry silver stain, which only detected 41%. The presented ISH is of comparable sensitivity to previously published immunohistochemical assays and is recommended for laboratories wishing to diagnose L. intracellularis infections in tissue sections but without access to antibodies".
1) Mcorist, S., Gebhart, C.J., Boid, R., Barns, S.M. “Characterization of Lawsonia intracellularis gen. nov., sp. nov., the Obligately Intracellular Bacterium of Porcine Proliferative Enteropathy.” 1995. Volume 45. p. 820-825.
2) Smith, DG.E., Mitchell, S.C., Nash, T., Rhind, S. “Gamma Interferon Influences Intestinal Epithelial Hyperplasia Caused by Lawsonia intracellularis Infection in Mice.” 2000. Volume 68. p. 6737–6743.
3) Jones, G. F., Ward, G.E., Murtaugh, M.P., Lin, G. and Gebhart, C.J. “Qualitative detection of Lawsonia intracellularis bacteria by PCR.” 2007.
4) NCBI Taxonomy Genome Project, http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=363253&lvl=3&lin=f&keep=1&srchmode=1&unlock.
5) PubMed search site, http://www.ncbi.nlm.nih.gov/entrez