Gastrointestinal infections: Edited by Nicholas J. Beeching and A. Clinton WhiteBacteroides spp. and diarrheaWick, Elizabeth C; Sears, Cynthia LAuthor Information Departments of Surgery and Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA Correspondence to Cynthia L. Sears, MD, CRB2 Bldg, Suite #1M.05, 1550 Orleans Street, Baltimore, MD 21231, USA Tel: +1 410 614 0141; fax: +1 410 614 8173; e-mail: [email protected] Current Opinion in Infectious Diseases: October 2010 - Volume 23 - Issue 5 - p 470-474 doi: 10.1097/QCO.0b013e32833da1eb Buy Metrics Abstract Purpose of review The purpose of this review is to describe recent progress in the understanding of the role of Bacteroides spp. in human diarrheal diseases and newer murine studies implicating certain Bacteroides spp. in colorectal cancer. Recent findings Bacteroides fragilis is the only strain of Bacteroides spp. associated with diarrheal disease. Toxin-producing strains of B. fragilis, termed enterotoxigenic Bacteroides fragilis (ETBF), are an established cause of diarrheal disease in people. The clinical syndrome associated with ETBF diarrheal disease encompasses abdominal pain, tenesmus and inflammatory diarrhea. Two new studies conducted in mice have further defined the chronic inflammatory response associated with ETBF infection and observed that in the multiple intestinal neoplasia mouse strain, heterozygotes for the adenomatous polyposis coli gene, ETBF infection enhances development of colonic tumors. Separate murine studies have begun to define the role of nontoxin-producing B. fragilis as a symbiont, serving possibly to protect the host from colonic inflammation. Summary B. fragilis remains the leading anaerobe in human disease. ETBF is emerging as an important cause of human diarrheal disease but additional epidemiologic studies are needed to better understand the role of ETBF human disease. © 2010 Lippincott Williams & Wilkins, Inc.