3rd Annual BMRP Investigator Meeting - Abstract
Pathogenic Yersinia DNA Detection in Crohn's Disease
Laura W. Lamps
Department of Pathology, University of Arkansas for Medical Sciences (Little Rock, Arkansas, U.S.A.)
Background: Pathogenic Yersinia species (enterocolitica and pseudotuberculosis) are one of the most common causes of bacterial enteritis in Western and Northern Europe. Geographic areas with a high incidence of Crohn’s disease (CD) have some of the highest rates of Yersinia infection. We developed the first molecular assays designed specifically to detect pathogenic Yersinia DNA and perform biogroup analysis in archival pathology materials. In preliminary studies, we detected pathogenic Yersinia DNA in 31% of 54 CD cases tested by PCR analysis. Currently, we are evaluating a cohort of CD cases from multiple geographical areas for the presence of Yersinia DNA and determining the biogroup (virulence) of the Yersinia-positive cases.
Materials and Methods: 144 archival CD specimens were retrieved. Following DNA extraction, two PCR assays were performed. The first detects chromosomal virulence gene [ail] fragments present only in pathogenic Yersinia species. The second detects plasmid encoded virulence genes (Yop); this assay also allows strain biogrouping and thus, assignment to a high or low virulence group. Sequencing analysis was performed to ensure that PCR products matched expected gene sequences.
Results: 82 cases have been analyzed as of October 2004, including 25 cases from the original pilot study and 57 newly accrued cases. 24% of cases (20/82) were Yop positive and 21% (17/82) were ail positive. In addition, evaluation of a small group of the Yersinia-positive cases showed that they contain DNA indicating a low virulence Yersinia biogroup (biogroup 2-5), whereas a control group of cases with fulminant, suppurative Yersinia infection contained a high virulence strain (biogroup 1B). Analysis of the remainder of the 144 cases, as well as correlation with histological and clinical data, is underway.
Conclusions: A significant percentage of CD cases are positive for pathogenic Yersinia DNA by PCR analysis. These preliminary data raise the possibility that Yersinia plays a role in the pathogenesis of CD. Genetically susceptible individuals may be vulnerable to bacterial “triggers” in their environment, which initiate an abnormal immune response. The presence of Yop DNA is particularly provocative, as Yop proteins modulate macrophage interactions in the inflammatory response. In addition, preliminary biogrouping data suggest a correlation between low virulence Yersinia biotypes and chronic inflammatory processes.