Small bowel bacterial overgrowth in adults: A potential contributor to intestinal failure

Abstract

Small bowel bacterial overgrowth (SBBO), in which colon-derived bacteria colonize the upper small bowel, is found in a wide variety of adult diseases associated with intestinal failure and dysfunction, including short bowel syndrome and other conditions following massive bowel resection, dysmotility disorders, and inflammatory bowel disease. SBBO also appears to be relatively common in the elderly, in whom it often goes unrecognized. SBBO is an important cause of malabsorption and thus may contribute to diarrhea and malnutrition. Elevated upper small intestinal aspirate colony counts remain the gold standard diagnostic test; a variety of noninvasive tests that detect elevated levels of breath hydrogen produced by bacterial fermentation of oral carbohydrate loads are also performed for diagnosis. Physicians commonly prescribe a variety of oral antibiotic regimens for documented or presumed SBBO. Additional research is needed to define the epidemiology, optimal diagnostic test(s), and therapeutic regimens for this condition.

Use of the lactose-[13C]ureide breath test for diagnosis of small bowel bacterial overgrowth: comparison to the glucose hydrogen breath test

“…The clinical manifestations and health consequences of the syndrome of SBBO can be quite debilitating [3,[8][9][10]12]. Because most predisposing conditions to SBBO persist life-long, it is more than evident that there is a need to develop a diagnostic tool that is sensitive and specific and, at the same time, noninvasive.…”

“…In the distal ileum there is normally an increase in concentration of bacteria to approximately 10 7 -10 8 aerobes and anaerobes. In the colon, a marked rise in anaerobes up to 10 11 organisms/mL, and of Enterobacteriaceae and other aerobes to 10 8 organisms/mL, is noted [3].…”

“…The reasons are manifold, ranging from diabetic neuropathy to surgical bypass, and have been extensively reviewed [3][4][5][6][7]. The SBBO syndrome may be characterized by chronic diarrhea, malabsorption and weight loss [3,[8][9][10]. SBBO is frequent in the elderly [11,12].…”

Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy

“…Intrinsic factors include: (1) secretion of gastric juice and bile, which have antibacterial effect; (2) peristaltic movement preventing adherence of bacteria into the intestinal mucosa; (3) normal gut defense including humoral and cellular mechanisms; (4) mucin production by intestinal mucosal epithelial cell inhibiting pathogenic bacteria; (5) gut antibacterial peptides such as defensins; and (6) ileocecal valve preventing retrograde translocation of bacteria from colon to the small intestine 24–26. Extrinsic factors include diet and drugs modulating gut flora, such as pre and probiotics, gastric acid suppressants such as proton pump inhibitors (PPIs), H 2 blockers, and antibiotics and drugs altering motility (prokinetics, anticholinergics, and opioids) 4,22,27–30. If, there is failure of any of the above-mentioned protective mechanisms, it may lead to development of SIBO (Fig.…”

“…Though quantitative culture of the upper gut aspirate has traditionally been used as the gold standard for the diagnosis SIBO, its limitations include difficulty and invasiveness, cost, contamination by oropharyngeal flora, and inability to culture as high as 70% bacteria colonizing the gut 2,13,30,31. Moreover, distribution of bacterial overgrowth may be patchy and upper gut aspirate may not be able to detect bacterial overgrowth in distal gut 30,32.…”