Evaluation of small bowel bacterial overgrowth

Abstract

Small bowel bacterial overgrowth historically has been associated with malabsorption syndrome attributed to deconjugation of bile acids in the upper small intestine. Recent reports raise the possibility that bacterial overgrowth may be a cause of watery diarrhea or irritable bowel syndrome. Quantitative culture of jejunal contents has been the gold standard for diagnosis, but a variety of indirect tests have been developed (and mostly discarded) over the years in an attempt to facilitate the diagnosis of small bowel bacterial overgrowth. These include breath tests and biochemical tests based on bacterial metabolism of various substrates. Problems with these indirect tests include rapid transit, which may cause substrate to reach the luxuriant bacterial flora in the colon, producing false positives and vagaries of the tests themselves, which may produce falsely negative results. The perfect test for small bowel bacterial overgrowth is yet to be devised.

Scintigraphy Demonstrates High Rate of False-positive Results From Glucose Breath Tests for Small Bowel Bacterial Overgrowth

“…The more widely used alternative is breath testing, which detects the production of hydrogen and/or methane that results from the digestion of swallowed carbohydrate loads by excessive bacteria in the small bowel. Breath testing is more likely than jejunal culture to identify cases of distal SBBO as well as pathologic bacterial M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT strains that may not culture well 6 . However, breath testing is often unable to distinguish small bowel from colonic metabolism of substrates and can be affected by clinical conditions that accelerate small bowel transit 1 .…”

Bacteria, Bones, and Stones: Managing Complications of Short Bowel Syndrome

“…SIBO is defined as a bacterial colony count >100,000 colony‐forming units per millimeter (10 5 CFU/mL) from the direct measurement of jejunal fluid or the presence of bacteria from colon or oropharynx in the SB . Nonspecific symptoms may suggest the presence of SIBO such as increase in watery or frothy stool output, especially if associated with bloating, flatulence, and abdominal pain.…”

“…How the test works is that the excessive bacteria in the SB will metabolize the substrate releasing hydrogen that is subsequently absorbed and then released in expired air. An increase in hydrogen in the breath sample after oral ingestion of the carbohydrate substrate, typically 10–20 ppm, indicates SIBO . However, the test results will be flawed in the setting of malabsorption because of the delivery of undigested substrate to the colon, making it impossible to differentiate between SB and colonic production of hydrogen.…”

Diarrhea: A Correct Algorithm of Doctor’s Actions

“…Патологическая колонизация тонкой кишки возникает при поступлении микроорганизмом из верх-них отделов ЖКТ или верхних дыхательных путей, при ретроградной транслокации бактерий из толстой кишки или при размножении условно-патогенных микроорга-низмов непосредственно в тонкой кишке при снижении ее защитных барьеров и нарушении переваривания и всасывания [22][23][24]. Развитие СИБР обусловлено как эндогенными, так и экзогенными факторами, приводящи-ми к нарушению колонизационной резистентности тон-кой кишки.…”

“…Эндогенными причинами СИБР могут быть практически любые заболевания ЖКТ, экзогенными -факторы внешней среды, лекарственные препараты, например ингибиторы протонной помпы или антибиоти-ки. Механизмы диареи при СИБР складываются из нескольких компонентов [3,24]: ■ Прямого повреждающего действия микробных токси-нов на структуру и активность мембранных ферментов, что приводит в нарушению мембранного гидролиза ну-триентов и осмотической диарее. ■ Стимуляции микробными токсинами секреции воды и электролитов энтероцитами, увеличения секреции, сни-жения абсорбции и развития секреторной диареи.…”