Luminal immunity in small-intestinal bacterial overgrowth and old age

Pediatric small intestine bacterial overgrowth in low-income countries

Small intestine bacterial overgrowth (SIBO) occurs when colonic quantities of commensal bacteria are present in the small bowel. SIBO is associated with conditions of disrupted gastrointestinal (GI) motility leading to stasis of luminal contents. Recent data show that SIBO is also found in children living in unsanitary conditions who do not have access to clean water. SIBO leads to impaired micronutrient absorption and increased GI permeability, both of which may contribute to growth stunting in children. SIBO also disrupts mucosal immunity and has been implicated in oral vaccination underperformance and the development of celiac disease. SIBO in the setting of the impoverished human habitats may be an under-recognized cause of pediatric morbidity and mortality in the developing world.

Small intestinal disorders in the elderly

The topic of gastroenterology (GI) in the elderly has been extensively reviewed. It takes special skill, patience and insight to interview the elderly, as well as to appreciate their altered physiology and interpretation of their presenting symptoms and signs, often against an extreme background of complex medical problems. The maldigestion and malabsorption coupled with altered motility contributes to the development of malnutrition. There generally a decrease of function of the GI tract, but there may be loss of adaptability in response to changes in diet or nutritional stress. Pathological alterations which might lead to minor overall intestinal functional variations in the young because of a normal process of adaptation, may lead to much more serious events in the elderly.

Small intestinal bacterial overgrowth: roles of antibiotics, prebiotics, and probiotics

Small intestinal bacterial overgrowth is common in intestinal failure. Its occurrence relates to alterations in intestinal anatomy, motility, and gastric acid secretion. Its presence may contribute to symptoms, mucosal injury, and malnutrition. Relationships between bacterial overgrowth and systemic sepsis are of potential importance in the intestinal failure patient because the direct translocation of bacteria across the intestinal epithelium may contribute to systemic sepsis: a phenomenon that has been well established in experimental animal models. The accurate diagnosis of bacterial overgrowth continues to present a number of challenges in clinical practice and especially so among patients with intestinal failure. The management of patients with bacterial overgrowth remains, for the most part, primarily empiric and comprises antibiotic therapy and correction of any associated nutritional deficiencies. Although evidence from experimental animal studies consistently indicates that probiotics exert barrier-enhancing, antibacterial, immune-modulating, and anti-inflammatory effects, which all could be benefits in small intestinal bacterial overgrowth and intestinal failure, their role in human beings remains to be evaluated adequately.

Small Bowel Bacterial Overgrowth: Presentation, Diagnosis, and Treatment

Small bowel bacterial overgrowth (SBBO) syndrome is associated with excessive numbers of bacteria in the proximal small intestine. The pathology of this condition involves competition between the bacteria and the human host for ingested nutrients. This competition leads to intraluminal bacterial catabolism of nutrients, often with production of toxic metabolites and injury to the enterocyte. A complex array of clinical symptoms ensues, resulting in chronic diarrhea, steatorrhea, macrocytic anemia, weight loss, and less commonly, protein-losing enteropathy. Therapy is targeted at correction of underlying small bowel abnormalities that predispose to SBBO and appropriate antibiotic therapy. The symptoms and signs of SBBO can be reversed with this approach.

Small bowel bacterial overgrowth: presentation, diagnosis, and treatment

Small bowel bacterial overgrowth (SBBO) syndrome is associated with excessive numbers of bacteria in the proximal small intestine. The pathology of this condition involves competition between the bacteria and the human host for ingested nutrients. This competition leads to intraluminal bacterial catabolism of nutrients, often with production of toxic metabolites and injury to the enterocyte. A complex array of clinical symptoms ensues, resulting in chronic diarrhea, steatorrhea, macrocytic anemia, weight loss, and less commonly, protein-losing enteropathy. Therapy is targeted at correction of underlying small bowel abnormalities that predispose to SBBO and appropriate antibiotic therapy. The symptoms and signs of SBBO can be reversed with this approach.

Small bowel disease in the elderly: diarrhoea and malabsorption

Diarrhoea and malabsorption are common problems in elderly persons. Worldwide, diarrhoea is the second leading cause of mortality. In the developed world, 85% of its mortality affects the elderly. The diagnostic work up for diarrhoea and malabsorption is more complex for the elderly than for the young patient. If diarrhoea persists for more than 24 h, oral rehydration solutions or intravenous fluids must be administered promptly in order to prevent hypotension and organ failure in the often multi-morbid patient. Both the immunocompromised patient and the severely affected out-patient should have stool culture performed. Malabsorption usually presents with weight loss, osteoporosis, anaemia, skin and neurological symptoms. The careful diagnostic work-up must aim at the identification of treatable disorders such as coeliac disease, Crohn's disease and bacterial overgrowth. Often, a detailed drug history is of help in identifying a readily treatable cause.

Small intestinal mucosal immunity and morphometry in luminal overgrowth of indigenous gut flora

OBJECTIVE

The aim of this study was to investigate the separate effects of indigenous oropharyngeal- and colonic-type flora on small intestinal mucosal immunity and morphometry in small intestinal bacterial overgrowth (SIBO).

METHODS

A duodenal aspirate and random biopsies of underlying mucosa were obtained from 52 adult subjects (age range, 18-90 yr; median, 60 yr) without disorders that may otherwise disturb small intestinal histology or mucosal immunity. Villus height, crypt depth, villus/crypt ratios, counts of intraepithelial lymphocytes (IELs) and lamina propria total mononuclear cells, IgA, IgM, and IgG plasma cells, mast cells, and B and T lymphocytes were determined in relation to the presence or absence of SIBO and the nature of the overgrowth flora in all subjects. CD4+ve and CD8+ve T-cell counts were determined in 24 subjects.

RESULTS

SIBO was present in 26 of 52 (50%) subjects. Overgrowth flora included colonic-type bacteria in 20 subjects and oropharyngeal-type flora alone in 6 subjects. Lamina propria IgA plasma cell counts were significantly increased in subjects with SIBO, irrespective of whether the overgrowth flora comprised oropharyngeal-type flora alone or included colonic-type bacteria. Neither villus height, crypt depth, villus/crypt ratios, nor total or other mononuclear cell counts in lamina propria differed significantly between subjects with and without SIBO, irrespective of the nature of the overgrowth flora. IEL counts were significantly higher than in culture-negative subjects only when the overgrowth flora included colonic-type bacteria. Even then, IEL counts were within a range currently considered normal. A significant, inverse correlation between advancing age and IEL counts became apparent after adjusting for the effect of SIBO of colonic-type flora.

CONCLUSIONS

SIBO of oropharyngeal- and colonic-type flora are associated with differing disturbances of local duodenal mucosa. Nonetheless, these would not be readily apparent during routine histological assessment. Old age independently influences duodenal IEL counts.

Relative deficiency in IgA production by duodenal explants from German shepherd dogs with small intestinal disease

Matched samples of serum, saliva and tears were collected from four groups of dogs; two of the groups were German shepherd dogs (GSDs) either with (Group 1) or without (Group 4) a variety of small intestinal disorders; the remaining two groups were dogs of other breeds, again with (Group 2) or without (Group 3) small intestinal disease. Capture ELISAs were used to measure IgG, IgM, IgA and albumin concentrations within these samples; intestinal humoral immune status of clinical cases was assessed by quantifying immunoglobulin production from duodenal explant cultures.There were no significant differences in IgG, IgM or IgA concentrations in serum, saliva or tears between the different groups of dog. Moreover, no significant differences were noted between groups for IgG, IgM and IgA salivary and tear secretory indices. IgA production by 24-h explant cultures was significantly lower in GSDs compared with non-GSDs with small intestinal disease (groups 1 and 2, respectively), but the numbers of lamina propria IgA(+) plasma cells in duodenal biopsies were not different between groups. These results suggest that there may be a relative deficiency in local IgA secretion in GSDs with small intestinal enteropathies, which is not reflected in either serum IgA concentrations, or in secretion at unaffected mucosal sites. It remains to be determined whether such a deficiency is a breed-related primary defect, or whether it arises secondary to the pathological processes within the intestinal mucosa.