S3006 Small Intestinal Bacterial Overgrowth After COVID-19 Infection : Official journal of the American College of Gastroenterology | ACG

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S3006 Small Intestinal Bacterial Overgrowth After COVID-19 Infection

Ali, Aleem BSc, MBBS1; Mathew, Reshmi DO2; Jadeja, Sonal DO2; Schey, Ron MD, FACG1; Masri, Ghania MD2

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The American Journal of Gastroenterology 116():p S1243-S1244, October 2021. | DOI: 10.14309/01.ajg.0000785556.20456.40
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Small intestinal bacterial overgrowth (SIBO) is defined as excessive bacteria in the small intestine with variable presentation ranging from mildly symptomatic to chronic diarrhea, weight loss and malabsorption. SIBO is typically evaluated with breath testing which relies on modification of a substrate such as lactulose by bacteria. Treatment of SIBO is directed at correcting the underlying case, providing nutritional support and treatment of the overgrowth.

Case Description/Methods:

A 63-year-old female reported a change in bowel habits six-weeks after being diagnosed with COVID-19 infection. The patient reported an eight-week history of abdominal discomfort with nausea and bloating associated with loose stools and mucus. Prior to this, she endorsed regular daily bowel motions with Bristol type 5. Her COVID infection was characterized by loss of tase and smell. The patient had no hypoxic episodes and as such steroids were deferred in favor of symptomatic management. Despite self-prescribed PPIs, added dietary supplements- probiotics, fiber and avoidance of dairy, her symptoms failed to improve. Stool testing had a negative culture, ova/cyst/parasites and negative C. difficile and fecal occult blood. EGD was a normal study. H. pylori testing returned negative. The patient underwent a lactulose breath test which returned positive suggestive of small intestinal bacterial overgrowth. The patient was prescribed Rifaximin with reported improvement in her symptoms.


Since the declaration of the COVID-19 pandemic in March 2020, the gastrointestinal (GI) manifestations related to Covid-19 have been widely reported. Commonly reported GI symptoms included nausea or vomiting, diarrhea and anorexia. Data suggest that the GI tract may be affected by SARS-CoV-2 on the basis that GI epithelial cells, particularly the enterocytes of the small intestine, express angiotensin-converting enzyme 2 (ACE2), the major receptor of SARS-CoV-2.COVID-19 predominantly manifest as pneumonia and in some cases, progression to ARDS. Studies have demonstrated that respiratory infections are associated with a change in the composition of gut microbiota, which plays a key role in the pathogenesis of sepsis and ARDS. A suggested hypothesis is that of SARS-CoV-2 leading to alteration of gut microbiota resulting in ‘gut dysbiosis’ which can result in excessive and altered bacterial overgrowth. Further research on SARS-CoV-2 and gut microbiota is needed to better understand the GI manifestation of the infection.

© 2021 by The American College of Gastroenterology