Alterations in Intestinal Microbial Flora and Human Disease

Mohamed Othman; Roberto Agüero; Henry C. Lin


Curr Opin Gastroenterol. 2008;24(1):11-16. 

In This Article

Small Intestinal Bacterial Overgrowth and Bacterial Translocation in Hepatic Encephalopathy

SIBO was diagnosed by abnormal gas excretion using the glucose breath test in more than 30% of cirrhotic patients.[49,50,51] Prevalence of spontaneous bacterial peritonitis (SBP) was higher in patients with SIBO, suggesting a causative relationship for this altered state of gut microbiota.[49,50] Another study, which used culture of jejunal secretions for the diagnosis of SIBO, reported a 60% prevalence of SIBO in 70 patients with cirrhosis; however, this study did not find an increased risk of SBP.[52] SIBO was found more frequently in rats with cirrhosis and bacterial translocation (93%) than rats with cirrhosis without bacterial translocation (33%).[53] Molecular studies in cirrhotic rats with SBP showed that the bacteria collected from mesenteric lymph nodes resulting from bacterial translocation were identical to that collected from ascitic fluid.[54] Although a human study failed to show the same relationship between bacterial translocation and SIBO, this may be a consequence of the difficulty in obtaining lymph node biopsies from different lymph nodes in humans or to the routine practice of administering antibiotics prior to any surgical procedure.[55] Norfloxacin, a poorly absorbed oral quinolone, was found to decrease bacterial translocation in rats with cirrhosis.[56] Accordingly, norfloxacin and trimethoprim-sulfamethoxazole were also effective in reducing the incidence of SBP in patients with cirrhosis.[57]

Changing the composition of microflora can affect minimal hepatic encephalopathy (MHE), one of the most common complications in patients with cirrhosis. Bacterial overgrowth occurs more frequently in patients with cirrhosis and MHE, compared with patients with cirrhosis but without MHE. Furthermore, these patients have higher concentrations of pathogenic Escherichia coli and Staphylococcus spp. among their fecal flora. A combination of probiotics and prebiotics reduced these pathogenic bacteria, increased nonurease-producing Lactobacillus spp. and reversed MHE in 50% of the patients.[58] Increasing the Bifidobacterium spp. count in the intestinal flora by administration of probiotics resulted in normalization of the fecal pH and decreased ammonia production in patients with cirrhosis, demonstrating the effectiveness of this probiotic to alter the intestinal microflora.[59]


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