***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Mycobacterium paratuberculosis is implicated as a possible cause of Crohn 's disease . However , due to lack of an appropriate diagnostic method , this has been a subject of significant controversy . Our aim was therefore to develop a multiplex polymerase chain reaction ( MPCR ) for the detection of M. paratuberculosis DNA in Crohn 's disease tissue . METHODS Biopsy sample s were collected by endoscopic forceps from terminal ileum , and genomic DNA was isolated . M. paratuberculosis-specific marker genes were amplified by using the present MPCR method . RESULTS Here we report a new MPCR for detection of M. paratuberculosis DNA in Crohn 's disease tissue . In this technique two genetic markers , IS900 and a newly described specific marker of MP2 , were amplified in a single tube simultaneously . The method was evaluated using biopsy specimens from 10 Crohn 's disease patients , 6 ulcerative colitis patients , and 21 irritable bowel syndrome patients . The patients were characterized by using st and ard clinical and histologic observations . The present MPCR method could not detect M. paratuberculosis DNA in the biopsy specimens . However , the marker genes were amplified from the sample s that were spiked with M. paratuberculosis before DNA extraction . The marker genes were also not detected in 10 closely related mycobacterial strains and human genomic DNA . CONCLUSIONS The present MPCR method is highly specific and can detect M. paratuberculosis DNA more reliably . These findings do not support an aetiologic role of M. paratuberculosis in Crohn 's disease BACKGROUND The etiology of Crohn 's disease remains unknown , but current research has concentrated on autoimmunity and /or mycobacterial infection . The polymerase chain reaction ( PCR ) enables the detection of genetic material even when very few microorganisms are present . METHODS A nested primer PCR for detection of a multi-copy insertional element ( IS900 ) specific for Mycobacterium paratuberculosis was applied to DNA extracted from fresh and from paraffin-embedded intestinal tissue obtained from patients undergoing surgery .  RESULTS In fresh intestinal tissue from 11 of 24 patients with Crohn 's disease , from 2 of 10 patients with ulcerative colitis , and from 3 of 28 patients with other colonic disorders , specific M. paratuberculosis DNA was found . In paraffin-embedded Crohn 's disease tissue the presence of specific M. paratuberculosis DNA was also increased . CONCLUSIONS Whether the presence of M. paratuberculosis is connected to the inflammatory bowel disease or is a mere coincidence can not be stated . We find this presence interesting and encouraging for further investigations PURPOSE : Mycobacterium paratuberculosis has been proposed as a causative agent in patients with Crohn 's disease . The purpose of this study was to determine whether M. paratuberculosis was present in tissue from patients with Crohn 's disease in a defined geographic area . METHODS : We prospect ively evaluated , using polymerase chain reaction and culture , whether M. paratuberculosis was present in 44 specimens ( 37 from intestinal mucosal biopsies and 7 from surgical resections ) from patients with Crohn 's disease , ulcerative colitis , or normal colonic mucosa . RESULTS : Of the 25 specimens tested from the 21 Crohn 's patients , only 1 positive specimen was noted , whereas the 8 specimens from the 5 ulcerative colitis patients and the 11 specimens from the 11 control patients failed to demonstrate a positive result with polymerase chain reaction . Cultures of all specimens revealed no growth of M. paratuberculosis . CONCLUSION : M. paratuberculosis was only rarely detected in biopsy or surgical specimens from patients with Crohn 's disease . These results do not support a common causative role of M. paratuberculosis in Crohn 's disease BACKGROUND / AIMS In order to assess the potential impact of bacterial eradication on recurrence rates , the prevalence of various enteropathogenic bacteria and toxins in chronic inflammatory bowel diseases ( CIBD ) was prospect ively examined . METHODOLOGY Stool , sera and gut tissue sample s from a total of 59 patients ( 33 males , 26 females ; mean age : 42 years + /- 14 ; 21 Crohn 's disease , 14 ulcerative colitis , 24 controls ) were examined for the presence of enteropathogenic bacteria by culture , immunoblotting and PCR . RESULTS Conventional cultures failed to detect obligate pathogenic bacteria . By PCR , mycobacteria were found in 85 % of all groups , with mycobacterium paratuberculosis not detected . Yersinia species were observed in 63 % of patients with Crohn 's disease , in 46 % of patients with ulcerative colitis , and in 36 % of the control patients . Pathogenic E. coli were identified in stool sample s of three patients with ulcerative colitis ( 21 % ) by amplifying the EAE-gene , one of whom exhibited shiga-like-toxin as well . CONCLUSIONS We concluded that mycobacteria do not play a causative role in CIBD . Yersinia species seem to persist in intestinal tissue in CIBD patients without adequate immune response and might , thus , contribute to tissue destruction . E. coli infections contribute to the disease process in a small group of patients with ulcerative colitis and their eradication might eliminate the need for immediate surgical intervention 
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The data confirms the observation that MAP is detected more frequently among CD patients compared with controls .
However , the pathogenic role of this bacterium in the gut remains uncertain .
Our analysis demonstrates that there is an association between MAP and CD , across many sites , by many investigators , and controlling for a number of factors ; however , this association remains controversial and inconclusive .