http://envismadrasuniv.org/Physiology/pdf/Gut%20flora%20in%20health%20and%20disease.pdf

Gut flora in health and disease

https://www.cell.com/cell/pdf/S0092-8674(05)00451-4.pdf

An immunomodulatory molecule of symbiotic bacteria directs maturation of the host immune system.

Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial

The gut is an obvious target for the development of functional foods, acting as it does as the interface between diet and the metabolic events which sustain life. The key processes in digestive physiology which can be regulated by modifying diet are satiety, the rate and extent of macronutrient breakdown and absorption from the small bowel, sterol metabolism, the colonic microflora, fermentation, mucosal function and bowel habit, and the gut immune system. The intestinal microflora is the main focus of many current functional foods. Probiotics are foods which contain live bacteria which are beneficial to health whilst prebiotics, such as certain non-digestible oligosaccharides which selectively stimulate the growth of bifidobacteria in the colon, are already on the market. Their claimed benefits are to alleviate lactose maldigestion, increase resistance to invasion by pathogenic species of bacteria in the gut, stimulate the immune system and possibly protect against cancer. There are very few reports of well-designed human intervention studies with prebiotics as yet. Certain probiotic species have been shown to shorten the duration of rotavirus diarrhoea in children but much more work is needed on the mechanism of immunomodulation and of competitive exclusion and microflora modification. The development of functional foods for the gut is in its infancy and will be successful only if more fundamental research is done on digestive physiology, the gut microflora, immune system and mucosal function.

/pdf/functional-food-science-and-gastrointestinal-physiology-and-4smhori2o4.pdf

Functional food science and gastrointestinal physiology and function

http://www.hmphanmi.com.cn/hmp/upload/event/study_4/3.pdf

The Key Role of Segmented Filamentous Bacteria in the Coordinated Maturation of Gut Helper T Cell Responses

Objectives. Antimicrobial treatment may disturb the colonization resistance of gastrointestinal microflora, which may induce clinical symptoms, most commonly diarrhea. The severity of antibiotic-associated diarrhea may range from a brief, self-limiting disease to devastating diarrhea with electrolyte disturbances, dehydration, crampy abdominal pain, pseudomembranous colitis, toxic megacolon, or even death. The incidence of diarrhea in children receiving a single antimicrobial treatment is unclear. In addition to more critical use of antimicrobials, adjunctive preventive measures to antibiotic-associated diarrhea are needed. The objective of this study was to evaluate the incidence of diarrhea after antimicrobial treatment in children with no history of antimicrobial use during the previous 3 months. Another aim of this study was to assess the preventive potential of Lactobacillus rhamnosus GG ( Lactobacillus GG ; American Type Culture Collection 53103), a probiotic strain with a documented safety record and a therapeutic effect in viral gastroenteritis on antibiotic-associated diarrhea. Methods. Oral antimicrobial agents were prescribed for the treatment of acute respiratory infections at the clinics of the Health Care Center of the City of Tampere or Tampere University Hospital, Finland, to 167 patients who were invited to participate in the study. Of the patients, 48 were lost to follow-up; therefore, the final study population consisted of 119 children from 2 weeks to 12.8 years of age (mean: 4.5 years). All study subjects met the inclusion criteria: they had not received any antimicrobial medication during the previous 3 months, they did not suffer from gastrointestinal disorders, and they did not need intravenous antimicrobial treatment. The patients were randomized to receive placebo or 2 × 10 10 colony-forming units of Lactobacillus GG in capsules given twice daily during the antimicrobial treatment. Lactobacillus GG and placebo capsules were indistinguishable in appearance and taste. The parents kept a daily symptom diary and recorded stool frequency and consistency at home for 3 months. Diarrhea was defined as at least three watery or loose stools per day for a minimum of 2 consecutive days. In the case of diarrhea, viral (adenovirus, rotavirus, calicivirus and astrovirus) and bacterial ( Salmonella, Shigella, Yersinia, Campylobacter, Clostridium difficile, Staphylococcus aureus, and yeasts) analyses were studied in fecal samples. The metabolic activity of the gut microflora was assessed by analysis of fecal urease, β-glucosidase, and β-glucuronidase activities. The primary outcome measure was diarrhea during the first 2 weeks after the beginning of the antimicrobial treatment, because this period most likely reflects the effects of antimicrobial use. Secondary outcome measures were the activities of fecal urease, β-glucuronidase, and β-glucosidase. Results. On the entire follow-up, 80% of any gastrointestinal symptoms were reported during the first 2 weeks after the beginning of the antimicrobial treatment. The incidence of diarrhea was 5% in the Lactobacillus GG group and 16% in the placebo group within 2 weeks of antimicrobial therapy (χ 2 = 3.82). The treatment effect (95% confidence interval) of Lactobacillus GG was −11% (−21%–0%). In diarrheal episodes, the viral and bacterial analyses were positive for Clostridium difficile in 2 cases and for Norwalk-like calicivirus in 3 cases. The age of the patients with diarrhea was between 3 months and 5 years in 75% of cases in both groups. The severity of diarrhea was comparable in the study groups, as evidenced by similar stool frequency (mean: 5 per day; range: 3–6) and the duration of diarrhea (mean: 4 days; range: 2–8). The activities of fecal urease and β-glucuronidase, but not β-glucosidase, changed significantly after the beginning of the antimicrobial treatment in the Lactobacillus GG group and in the placebo group alike. The decrease in urease and β-glucuronidase activities was reversible in patients with no diarrhea, but in patients with diarrhea, the modifications in gut microflora were more profound and prolonged. The activities of the three enzymes were normalized within 3 weeks, evidenced by stable enzyme activities in samples collected 3 weeks, 1 month, and 3 months after the beginning of the antimicrobial treatment, compared with those obtained before treatment. Discussion. In the present study, after a single antimicrobial treatment, the incidence of diarrhea was 16%. The higher incidence of antibiotic-associated diarrhea in previous reports may be attributable to a recent antimicrobial therapy that disturbs intestinal flora and exposes to complications. Also, in the present study, changes in the metabolic activity of the intestinal flora were observed, evidenced by a transient decline in fecal enzyme activities. Different probiotic preparations, including lactobacilli, are recommended frequently to prevent antibiotic-associated diarrhea. Although probiotics have been shown to be efficient in the prevention and the treatment of viral gastroenteritis, their usefulness during antimicrobial therapy in children has not been elucidated before. We observed that the administration of Lactobacillus GG to children receiving antimicrobial therapy for respiratory infection reduced the incidence of antibiotic-associated diarrhea to one third. The beneficial effect may be mediated by a number of functions of probiotics, ie, production of antimicrobial substances, local competition of adhesion receptors and nutrients, and stimulation of intestinal antigen specific and nonspecific immune responses. Conclusion. A probiotic strain, Lactobacillus GG , is effective in the prevention of diarrhea in children receiving antimicrobial treatment to respiratory infections.

https://pediatrics.aappublications.org/content/pediatrics/104/5/e64.full.pdf

Prophylactic Lactobacillus GG reduces antibiotic-associated diarrhea in children with respiratory infections: a randomized study.

https://www.gastrojournal.org/article/0016-5085(93)91059-Q/pdf

Lactobacillus casei strain GG reverses increased intestinal permeability induced by cow milk in suckling rats

Background: Recent data have outlined a relationship between the composition of the intestinal microflora and allergic inflammation, and demonstrated the competence of probiotics in downregulation of such inflammation Aims: Our aims were to characterise the relationship between gut microbes and the extent of allergic sensitisation and to assess whether the efficacy of bifidobacterial supplementation in the treatment of allergy could relate to modulation of the intestinal microbiota Methods: This randomised study included 21 infants with early onset atopic eczema of whom eight were intolerant (highly sensitised group (HSG)) and 13 tolerant (sensitised group (SG)) to extensively hydrolysed whey formula (EHF) In the SG, six were weaned to EHF without (placebo group (PG)) and seven to EHF with Bifidobacterium lactis Bb-12 supplementation (bifidobacteria treated group (BbG)) The faecal microflora of infants in the HSG was analysed only before weaning whereas in the SG the faecal microflora was analysed both before and after weaning Results: Infants in the HSG had greater numbers of lactobacilli/enterococci than those in the SG Serum total IgE concentration correlated directly with Escherichia coli counts in all infants and with bacteroides counts in the HSG, indicating that the presence of these bacteria is associated with the extent of atopic sensitisation The effect of supplementation was characterised as a decrease in the numbers of Escherichia coli and protection against an increase in bacteroides numbers during weaning Conclusions: These data indicate that bifidobacterial supplementation appears to modify the gut microbiota in a manner that may alleviate allergic inflammation Further studies are needed to confirm this conclusion

https://gut.bmj.com/content/gutjnl/51/1/51.full.pdf

Aberrant composition of gut microbiota of allergic infants: a target of bifidobacterial therapy at weaning?

OBJECTIVE. Rectal bleeding is an alarming symptom and requires additional investigation. In infants it has been explained mainly by hypersensitivity. In addition to dietary antigens, intraluminal microbial agents challenge the immature gut mucosa. Although controlled in the mature gut, these antigens may induce inflammation in the developing gastrointestinal tract. The objectives of this study were to evaluate prospectively the clinical course of rectal bleeding and evaluate the impact of cow9s milk allergy and aberrant gut microbiota on the condition. Because withdrawal of cow9s milk antigens from the infants9 diet is used as a first treatment without evidence of its efficacy, we also aimed to asses the effect of a cow9s milk–elimination diet on the duration of rectal bleeding. METHODS.The study involved 40 consecutive infants (mean age: 2.7 months) with visible rectal bleeding during a 2-year period at the Tampere University Hospital Department of Pediatrics. Most of the infants (68%) were fully breastfed. At enrollment the infants were randomly allocated to receive a cow9s milk–elimination diet (n = 19) or continue their previous diet (n = 21) for 1 month. Findings of colonoscopy, fecal bacterial culture, fluorescence in situ hybridization of selected gut genera, specific detection of fecal enteroviruses, rotaviruses, and adenoviruses, fecal electron microscopy for viruses, and mucosal electron microscopy for viruses were assessed. During each visit the severity of atopic eczema, if any, was assessed according to the SCORAD method. In evaluating the extent of sensitization, serum total immunoglobulin E (IgE) and specific IgE and skin-prick tests for cow9s milk, egg, and wheat were studied. Cow9s milk allergy was diagnosed by elimination and provocation testing. Five patients were hospitalized; all others were treated on an outpatient basis. The follow-up visits were scheduled 1 month later and at the age of 1 year. Sixty-four healthy reference infants were selected as controls according to the following criteria: age and timing of fecal sampling being identical to within 1 month. RESULTS. Altogether, 32 (80%) infants manifested bloody stools during follow-up (mean [range]: 2.1 [1–15] per day). The mean number of days with rectal bleeding on follow-up was 6. Typically, bloody stools occurred irregularly, for which reason the mean time to the last occurrence of rectal bleeding was 24 (range: 1–85) days from admission. Atopic eczema at presentation or during follow-up was diagnosed in 38% of the infants. Increased specific IgE concentrations or a positive skin-prick test were uncommon. The growth of the infants was normal on admission and during follow-up. Colonoscopy revealed typically focal mucosal erythema and aphthous ulcerations. The mucosa appeared normal in less than half of the patients. No anorectal fissures or colonic polyps were found. Light microscopy revealed that the overall architecture of the mucosa was well maintained. Acute inflammation or postinflammatory state and focal infiltration of eosinophils in the lamina propria were the most common abnormalities. A cow9s milk–elimination diet did not affect the duration of rectal bleeding. Cow9s milk allergy was diagnosed in 7 (18%) patients. Virus-particle aggregates were found in the microvillus layer of the colon epithelium in 8 cases. The surface epithelium of the virus-positive colon biopsy specimens regularly showed degenerative changes in the microvillus layer and epithelial cells. Electron microscopy study of the colon biopsies disclosed virus particles (30 nm in diameter) on the surface of epithelial cells. Virus particles or RNA were present in feces in only a minority of the patients. All fecal cultures were negative for Salmonella, Shigella, and Yersinia. Campylobacter jejuni was found in the feces of 1 patient, and fecal cultures were positive for Clostridium difficile in 4 patients, Staphylococcus aureus in 8 patients, and yeast in 2 patients. Fluorescence in situ hybridization revealed that at the time of admission the total numbers of bacteria and the numbers of bifidobacteria and lactobacilli in feces were lower in the patients compared with controls. The fecal concentrations of microbes characterized in this study (Bacteroides, bifidobacteria, Clostridium, lactobacilli, and enterococci) did not differ significantly between the time of admission and the second visit in the patients or controls. At the age of 1 year, 7 patients still suffered from cow9s milk allergy, 5 of whom also suffered from multiple food allergies. Atopic eczema and histopathologically confirmed inflammation of the colonic mucosa at presentation were associated with persistence of cow9s milk allergy at the age of 1 year. No patients exhibited gastrointestinal complaints or visible blood in stools. CONCLUSIONS. Rectal bleeding in infants is generally a benign and self-limiting disorder. Bloody stools occurred irregularly for only a few days during the following months. As in a previous report, most infants were exclusively breastfed. In the majority of the patients the cause of the condition remains unknown. An association with viruses can be seen in some patients. The microbes that commonly lead to bloody diarrhea in older children and adults, Salmonella, Shigella, and Yersinia, were absent in the present material. The low bifidobacterial numbers in fecal samples may indicate a significant aberrance that may provide a target for probiotic intervention to normalize gut microbiota. The gut microbiota overall seemed stable, because the numbers of major groups of microbiota tested did not change significantly between the time of admission and after 1 month. Cow9s milk allergy among these patients is more uncommon than previously believed. Cow9s milk challenge is thus essential in infants who become symptom-free during a cow9s milk–free diet to reduce the number of false-positive cow9s milk–allergy diagnoses.

Rectal Bleeding in Infancy: Clinical, Allergological, and Microbiological Examination

We assessed the fecal microflora of 10 healthy infants and 27 infants with atopic eczema during breast-feeding and after weaning. The atopic infants had less frequently Gram-positive species among the most predominant aerobes and smaller total cell counts. Further differences were associated with more extensive manifestations, seen as higher bacteroides and lower bifidobacteria counts. Weaning resulted in decreased bacteroides counts in atopic and total cell counts in healthy infants and diminished predominance by bifidobacteria in both. In conclusion, the most prominent question raised by these data is whether Gram-positive bacteria may have distinctive importance in protection against atopic sensitization. Further studies aiming to answer this question are warranted.

Taina Arvola

Papers

Prophylactic Lactobacillus GG reduces antibiotic-associated diarrhea in children with respiratory infections: a randomized study.

Lactobacillus casei strain GG reverses increased intestinal permeability induced by cow milk in suckling rats

Aberrant composition of gut microbiota of allergic infants: a target of bifidobacterial therapy at weaning?

Rectal Bleeding in Infancy: Clinical, Allergological, and Microbiological Examination

Characterizing the composition of intestinal microflora as a prospective treatment target in infant allergic disease.