Impaired colonic fermentation of carbohydrate after ampicillin

Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS)

BACKGROUND

There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.

PURPOSE

However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics. In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

High fat intake sustains sorbitol intolerance after antibiotic-mediated Clostridia depletion from the gut microbiota

Carbohydrate intolerance, commonly linked to the consumption of lactose, fructose, or sorbitol, affects up to 30% of the population in high-income countries. Although sorbitol intolerance is attributed to malabsorption, the underlying mechanism remains unresolved. Here, we show that a history of antibiotic exposure combined with high fat intake triggered long-lasting sorbitol intolerance in mice by reducing Clostridia abundance, which impaired microbial sorbitol catabolism. The restoration of sorbitol catabolism by inoculation with probiotic Escherichia coli protected mice against sorbitol intolerance but did not restore Clostridia abundance. Inoculation with the butyrate producer Anaerostipes caccae restored a normal Clostridia abundance, which protected mice against sorbitol-induced diarrhea even when the probiotic was cleared. Butyrate restored Clostridia abundance by stimulating epithelial peroxisome proliferator-activated receptor-gamma (PPAR-γ) signaling to restore epithelial hypoxia in the colon. Collectively, these mechanistic insights identify microbial sorbitol catabolism as a potential target for approaches for the diagnosis, treatment, and prevention of sorbitol intolerance.

Auto-Brewery Syndrome and General Anesthesia: A Case Report

Auto-brewery syndrome (ABS) is a rare condition in which ethanol is endogenously fermented by fungi in the gut following a carbohydrate-rich meal, resulting in intoxication. We present a case of a patient with ABS successfully undergoing general anesthesia for symptomatic wisdom tooth extraction. During previous anesthetics, the patient had experienced postoperative nausea and vomiting (PONV) and awareness under anesthesia. Patients with ABS can be optimized for anesthesia by assessing hepatic function, avoiding perioperative oral carbohydrates, increasing anesthetic depth, multimodal PONV prophylaxis, and avoidance of broad-spectrum antibiotics.

Gut fermentation seems to promote decompression sickness in humans

Massive bubble formation after diving can lead to decompression sickness (DCS) that can result in neurological disorders. In experimental dives using hydrogen as the diluent gas, decreasing the body's H2burden by inoculating hydrogen-metabolizing microbes into the gut reduces the risk of DCS. In contrast, we have shown that gut bacterial fermentation in rats on a standard diet promotes DCS through endogenous hydrogen production. Therefore, we set out to test these experimental results in humans. Thirty-nine divers admitted into our hyperbaric center with neurological DCS (Affected Divers) were compared with 39 healthy divers (Unaffected Divers). Their last meal time and composition were recorded. Gut fermentation rate was estimated by measuring breath hydrogen 1-4 h after the dive. Breath hydrogen concentrations were significantly higher in Affected Divers (15 ppm [6–23] vs. 7 ppm [3–12]; P = 0.0078). With the use of a threshold value of 16.5 ppm, specificity was 87% [95% confidence interval (CI) 73–95] for association with neurological DCS onset. We observed a strong association between hydrogen values above this threshold and an accident occurrence (odds ratio = 5.3, 95% CI 1.8–15.7, P = 0.0025). However, high fermentation potential foodstuffs consumption was not different between Affected and Unaffected Divers. Gut fermentation rate at dive time seemed to be higher in Affected Divers. Hydrogen generated by fermentation diffuses throughout the body and could increase DCS risk. Prevention could be helped by excluding divers who are showing a high fermentation rate, by eliminating gas produced in gut, or even by modifying intestinal microbiota to reduce fermentation rate during a dive.

A Review of Management of Clostridium difficile Infection: Primary and Recurrence

Clostridium difficile infection (CDI) is a potentially fatal illness, especially in the elderly and hospitalized individuals. The recurrence and rates of CDI are increasing. In addition, some cases of CDI are refractory to the currently available antibiotics. The search for improved modalities for the management of primary and recurrent CDI is underway. This review discusses the current antibiotics, fecal microbiota transplantation (FMT) and other options such as immunotherapy and administration of non-toxigenic Clostridium difficile (CD) for the management of both primary and recurrent CDI.

Faecal microbiota composition and host-microbe cross-talk following gastroenteritis and in postinfectious irritable bowel syndrome

BACKGROUND

About 10% of patients with IBS report the start of the syndrome after infectious enteritis. The clinical features of postinfectious IBS (PI-IBS) resemble those of diarrhoea-predominant IBS (IBS-D). While altered faecal microbiota has been identified in other IBS subtypes, composition of the microbiota in patients with PI-IBS remains uncharacterised.

OBJECTIVE

To characterise the microbial composition of patients with PI-IBS, and to examine the associations between the faecal microbiota and a patient's clinical features.

DESIGN

Using a phylogenetic microarray and selected qPCR assays, we analysed differences in the faecal microbiota of 57 subjects from five study groups: patients with diagnosed PI-IBS, patients who 6 months after gastroenteritis had either persisting bowel dysfunction or no IBS symptoms, benchmarked against patients with IBS-D and healthy controls. In addition, the associations between the faecal microbiota and health were investigated by correlating the microbial profiles to immunological markers, quality of life indicators and host gene expression in rectal biopsies.

RESULTS

Microbiota analysis revealed a bacterial profile of 27 genus-like groups, providing an Index of Microbial Dysbiosis (IMD), which significantly separated patient groups and controls. Within this profile, several members of Bacteroidetes phylum were increased 12-fold in patients, while healthy controls had 35-fold more uncultured Clostridia. We showed correlations between the IMD and expression of several host gene pathways, including amino acid synthesis, cell junction integrity and inflammatory response, suggesting an impaired epithelial barrier function in IBS.

CONCLUSIONS

The faecal microbiota of patients with PI-IBS differs from that of healthy controls and resembles that of patients with IBS-D, suggesting a common pathophysiology. Moreover, our analysis suggests a variety of host-microbe associations that may underlie intestinal symptoms, initiated by gastroenteritis.

Diarrhea caused by carbohydrate malabsorption

This article will focus on the role of the colon in the pathogenesis of diarrhea in carbohydrate malabsorption or physiologically incomplete absorption of carbohydrates, and on the most common manifestation of carbohydrate malabsorption, lactose malabsorption. In addition, incomplete fructose absorption, the role of carbohydrate malabsorption in other malabsorptive diseases, and congenital defects that lead to malabsorption will be covered. The article concludes with a section on diagnostic tools to evaluate carbohydrate malabsorption.

Colonoscopic versus nasogastric fecal transplantation for the treatment of Clostridium difficile infection: a review and pooled analysis

BACKGROUND

Fecal microbiota transplantation (FMT) has been demonstrated to be highly effective for the treatment of recurrent Clostridium difficile infection (CDI). However, the best route of administration has not been established. We present a pooled analysis of the reported cases of CDI treated with FMT via colonoscopy or nasogastric tube (NGT) to evaluate treatment efficacy.

METHODS

PubMed was searched for English-written articles published up to December 2011. Studies that reported cases of FMT for recurrent CDI using either colonoscopy or NGT-guided fecal infusion were reviewed.

RESULTS

A total of 182 patients from 12 published studies were identified; 148 patients received FMT via colonoscopy (colonoscopy group) and 34 patients received FMT via NGT (NGT group). The median age in the colonoscopy group as compared with the NGT group was 72 and 82 years, respectively. There were differences regarding pre-FMT treatment for CDI; 134 patients (90.5 %, 134/148) received lavage with/without antibiotic in the colonoscopy group and 34 patients (100.0 %, 34/34) received antibiotic without lavage in the NGT group, P < 0.001. A higher stool volume was used for FMT in the colonoscopy group (121 patients, 81.8 %, used 100-400 ml) than in the NGT group (33 patients, 97.0 %, used <100 ml), P < 0.001. The treatment efficacy did not differ significantly; 93.2 % (138/148) success for the colonoscopy group as compared to 85.3 % success (29/34) for the NGT group, P = 0.162. Recurrence of CDI after FMT was also similar in both the colonoscopy group (8/148 5.4 %) versus the NGT group (2/34, 5.9 %), P = 1.000.

CONCLUSIONS

Despite procedural differences, FMT via colonoscopy or NGT appears to be highly effective and safe for the management of recurrent CDI.

Role of colonic short-chain fatty acid transport in diarrhea

Short-chain fatty acids (SCFA) are the major anion in stool and are synthesized from nonabsorbed carbohydrate by the colonic microbiota. Nonabsorbed carbohydrate are not absorbed in the colon and induce an osmotically mediated diarrhea; in contrast, SCFA are absorbed by colonic epithelial cells and stimulate Na-dependent fluid absorption via a cyclic AMP-independent process involving apical membrane Na-H, SCFA-HCO(3), and Cl-SCFA exchanges. SCFA production represents an adaptive process to conserve calories, fluid, and electrolytes. Inhibition of SCFA synthesis by antibiotics and administration of PEG, a substance that is not metabolized by colonic microbiota, both result in diarrhea. In contrast, increased production of SCFA as a result of providing starch that is relatively resistant to amylase digestion [so-called resistant starch (RS)] to oral rehydration solution (RS-ORS) improves the efficacy of ORS and represents an important approach to improve the effectiveness of ORS in the treatment of acute diarrhea in children under five years of age.

Pharmaceutical probiotics for the treatment of anaerobic and other infections

Pharmaceutical probiotics have been used as alternative treatments or preventative therapies for a variety of clinical diseases. The overuse of antibiotics and emergence of multiple-antibiotic resistant pathogens has refocused clinical attention on the field of probiotics. Anaerobic infections which seem to respond well to probiotics are infections which involve the disruption of normal microbial flora. Gastrointestinal infections (travelers' diarrhea, antibiotic-associated diarrhea,Clostridium difficile disease, rotavirus diarrhea) have been studied using the following pharmaceutical probiotics:Saccharomyces boulardii, Lactobacillus casei GG, Lactobacillus acidophilus, Lactobacillus bulgaricus, Bifidobacterium bifidum, Streptococcus thermophilus and Enterococcus faecium. Vaginitis has been experimentally studied using L. acidophilus and L. casei GG. The efficacy, safety and mechanisms of action of these various probiotics are reviewed. Requirements for drug approval are similar for biologic probiotics and new drug entities and these requirements involve preclinical tolerability studies, pharmacokinetic studies and large, well-controlled blinded clinical trials.

Role of motility in chronic diarrhoea

Patients complaining of 'chronic diarrhoea' usually mean the passage of loose, urgent stools. Chronic diarrhoea is a feature of malabsorption; it may also be seen in the 'dumping syndrome' which follows gastric surgery, small intestinal bacterial overgrowth, bile salt malabsorption and in malabsorption of simple sugars including most commonly lactose, fructose and sorbitol. Excessively rapid entry of chyme into the small or large intestine generates propulsive motor patterns leading to accelerated transit. Inflammation is associated with decreased normal mixing motor patterns but increased propulsive motility including high amplitude propagated contractions (HAPCs). Evidence for abnormal small intestinal motility in the diarrhoea associated with irritable bowel syndrome (IBS) is conflicting and any difference appears small. Increased colonic HAPCs with increased propulsion is seen in IBS with diarrhoea (IBS-D). Stress-induced colonic motility is increased in IBS-D with hyper-responsiveness to corticotrophin releasing factor (CRF). Long-lasting increases in mucosal serotonin availability may contribute to the chronic diarrhoea seen in IBS-D and coeliac disease. Treatments for abnormal motility in chronic diarrhoea include those designed to correct specific underlying abnormalities including octreotide, antibiotics, colestyramine, specific food avoidance and anti-inflammatory agents. There are also treatments aimed primarily at altering motility directly including opiates, 5HT3 receptor antagonists and amitriptyline.

Short-chain fatty acids: ready for prime time?

The concept of colonic health has become a major target for the development of functional foods such as probiotics, prebiotics, and synbiotics. These bioactive agents have a profound effect on the composition of the microflora, as well as on the physiology of the colon, and display distinct health benefits. Dietary carbohydrates escaping digestion/absorption in the small bowel and prebiotics undergo fermentation in the colon and give rise to short-chain fatty acids (SCFA). As the main anions of the colon and the major source of energy for colonocytes, SCFA are rapidly absorbed by nonionic diffusion mostly but also by active transport mediated by a sodium-coupled transporter, thereby fostering the absorption of sodium and water. SCFA in general and butyrate in particular enhance the growth of lactobacilli and bifidobacteria and play a central role on the physiology and metabolism of the colon. The effect of prebiotics on cell proliferation, differentiation, apoptosis, mucin production, immune function, mineral absorption, lipid metabolism, and gastrointestinal (GI) peptides has been well documented experimentally. These effects seem to be largely mediated by SCFA, but evidence from human studies remains inconsistent. The food industry is making a leap of faith in their efforts to commercialize prebiotics and exploit potential health benefits. The future lies with the design of studies to further explore basic mechanisms, and gene expression in particular, but emphasis should be placed on human intervention trials.

Effects of an osmotically active agent on colonic transit

It is unknown if sorbitol, a widely used laxative agent, accelerates colonic transit, and if these effects are modified by concomitant meal ingestion. Colonic transit was assessed by (111)In scintigraphy in 40 healthy subjects. After a 24-h scan, subjects received sorbitol (30 mL of 70% solution) or dextrose (30 mL of 70% solution), administered with or without a meal. Colonic transit, breath hydrogen excretion, and symptom scores were recorded for 4 h thereafter. VAS scores for flatulence, but not other symptoms increased (P = 0.004) by 13.1 +/- 6.3 mm (mean +/- SEM) on a 100 mm scale after sorbitol alone or sorbitol with a meal (by 18.9 +/- 7.2 mm), but not after dextrose. After adjusting for GC(24), sorbitol accelerated (P < 0.001) colonic transit (GC(28) = 3.0 +/- 0.3) compared with dextrose (GC(28) = 2.2 +/- 0.2), regardless of meal ingestion. Breath hydrogen excretion was correlated with the change in colonic transit (r = 0.52, P < 0.01) and with flatulence (r = 0.45, P = 0.003) after sugar ingestion. In healthy subjects, sorbitol accelerated colonic transit and increased flatulence but not other symptoms within 4 h, regardless of meal intake.

Management of diverticular disease: is there room for rifaximin?

Treatment of symptomatic diverticular disease of the colon is aimed at the relief of symptoms and the prevention of major complications. The efficacy of fiber supplementation and of anticholinergic and spasmolytic agents remains controversial. Antibiotics are commonly used in the treatment of inflammatory complications of diverticular disease. Data from open labelled and randomized controlled trials do suggest the efficacy of rifaximin in obtaining symptomatic relief in patients with diverticular disease. Approximately 30% therapeutic gain compared to fiber supplementation only can be expected after one year of intermittent treatment with rifaximin. Considering the safety and tolerability of rifaximin, this drug can be recommended for patients with symptomatic uncomplicated diverticular disease.

Antibiotic-associated diarrhea and pseudomembranous colitis: are they less common with poorly absorbed antimicrobials?

Diarrhea is a well-known complication of antibiotic therapy. Rates of antibiotic-associated diarrhea (AAD) vary from 5 to 25%. Some antibiotics are more likely to cause diarrhea than others, specifically, those that are broad spectrum and those that target anaerobic flora. This paper reviews the effects of antibiotics on the fecal flora as well as host factors which contribute to AAD. Clinical features and treatment of AAD are also described. Prevention of AAD rests on wise antibiotic policies, the use of probiotics and prevention of acquisition in the hospital setting. Data from clinical trials suggest that poorly absorbed antimicrobials might have a decreased risk of causing AAD and Clostridium difficile-associated disease, as concluded from studies of antibiotics used for preoperative bowel decontamination and poorly absorbed antibiotics used for traveler's diarrhea. Controlled trials would prove this but are not yet available. Probiotics may be a good adjunct to poorly absorbed antibiotics to minimize the risk of diarrhea associated with antibiotics.

Microbial-gut interactions in health and disease. Antibiotic-associated diarrhoea

Most cases of antibiotic-associated diarrhoea (AAD) are directly or indirectly due to the alteration of gut microflora by antibiotics. 'Functional' diarrhoea, usually limited to a mild and brief change in stool frequency, is considered as the most frequent pattern of AAD. Reduced carbohydrate fermentation and impaired metabolism of bile acids have been claimed as the potential causes of this transient digestive discomfort but a critical analysis of the data supporting these theories is necessary. Alternatively, changes in the gut flora ecosystem allow pathogens to proliferate. Clostridium difficile is responsible for approximately 10% of cases of AAD and almost all cases of antibiotic-associated pseudomembranous colitis. The level of evidence which supports the potential responsibility of other candidate pathogens (Klebsiella oxytoca, enterotoxin-producing Clostridium perfringens and Staphylococcus aureus, Candida) needs to be appreciated according to the updated postulates of causality relationships between a bacterium and a disease.

Antibiotic-associated diarrhoea and Clostridium difficile in the community

BACKGROUND

Clostridium difficile is the main cause of nosocomial infectious diarrhoea and the causative agent of antibiotic-associated colitis. The involvement of C. difficile infection in antibiotic-associated diarrhoea in the community is poorly documented.

METHODS

We studied prospectively 266 adult out-patients in the Paris (France) area who were prescribed a 5-10-day course of antimicrobial chemotherapy. Stools were screened for C. difficile before and 14 days after the start of treatment by standard culture, toxigenic culture and testing for the cytopathic effect of toxin B. Patients were requested to note daily stool frequency and consistency. Diarrhoea was defined as the passage of at least three loose stools per day.

RESULTS

Forty-six (17.5%) of the 262 assessable patients had diarrhoea during the study period. Diarrhoea was mild and self-limited in all patients, and lasted for only 1 day in 65.6% of cases. C. difficile was isolated before and after treatment from one patient, who did not develop diarrhoea. C. difficile was detected only on day 14 in 10 patients (3.8%). The isolate was toxin producing in seven patients. Four of these seven patients had mild self-limited diarrhoea. Toxin-producing C. difficile was isolated significantly more frequently from patients who had diarrhoea than from those who were diarrhoea free (8.7% vs. 1.4%, P = 0.02).

CONCLUSION

The acquisition of toxin-producing C. difficile appears to be frequent during antimicrobial chemotherapy in the community [estimated rate of 2700 (1150-5400) cases per 100 000 exposures to antibiotics]. However, C. difficile is not the main agent of mild antibiotic-associated diarrhoea in out-patients.

Recurrent Clostridium difficile colitis: case series involving 18 patients treated with donor stool administered via a nasogastric tube

Clostridium difficile-associated diarrhea and colitis have emerged as major complications associated with use of systemic antimicrobials. In this study, the medical records for 18 subjects who received donor stool by nasogastric tube for recurrent C. difficile infection during a 9-year period at a single institution were retrospectively reviewed. During the period between the initial diagnosis of C. difficile colitis and the stool treatments, the 18 subjects received a total of 64 courses of antimicrobials (range, 2-7 courses; median, 3 courses). During the 90 days after receipt of treatment with stool, 2 patients died of unrelated illnesses. One of the 16 survivors experienced a single recurrence of C. difficile colitis during 90-day follow-up. No adverse effects associated with stool treatment were observed. Patients with recurrent C. difficile colitis may benefit from the introduction of stool from healthy donors via a nasogastric tube.

GI complications in patients receiving mechanical ventilation

Mechanical ventilation (MV) can be lifesaving by maintaining gas exchange until the underlying disorders are corrected, but it is associated with numerous organ-system complications, which can significantly affect the outcome of critically ill patients. Like other organ systems, GI complications may be directly attributable to MV, but most are a reflection of the severity of the underlying disease that required intensive care. The interactions of the underlying critical illness and MV with the GI tract are complex and can manifest in a variety of clinical pictures. Incorporated in this review are discussions of the most prevalent GI complications associated with MV, and current diagnosis and management of these problems.

Non-absorbable antibiotics for managing intestinal gas production and gas-related symptoms

BACKGROUND

Simethicone, activated charcoal and antimicrobial drugs have been used to treat gas-related symptoms with conflicting results.

AIM

To study the relationship between gaseous symptoms and colonic gas production and to test the efficacy of rifaximin, a new non-absorbable antimicrobial agent, on these symptoms.

METHODS

Intestinal gas production was measured by hydrogen (H2) and methane (CH4) breath testing after lactulose in 21 healthy volunteers and 34 functional patients. Only the 34 functional patients took part in a double-blind, double-dummy controlled trial, receiving, at random, rifaximin (400 mg b.d per 7 days), or activated charcoal (400 mg b.d per 7 days). The following parameters were evaluated at the start of the study and 1 and 10 days after therapy: bloating, abdominal pain, number of flatus episodes, abdominal girth, and cumulative breath H2 excretion.

RESULTS

Hydrogen excretion was greater in functional patients than in healthy volunteers. Rifaximin, but not activated charcoal, led to a significant reduction in H2 excretion and overall severity of symptoms. In particular, in patients treated with rifaximin, a significant reduction in the mean number of flatus episodes and of mean abdominal girth was evident.

CONCLUSIONS

In patients with gas-related symptoms the colonic production of H2 is increased. Rifaximin significantly reduces this production and the excessive number of flatus episodes.

Drug-induced diarrhoea

Diarrhoea is a relatively frequent adverse event, accounting for about 7% of all drug adverse effects. More than 700 drugs have been implicated in causing diarrhoea; those most frequently involved are antimicrobials, laxatives, magnesium-containing antacids, lactose- or sorbitol-containing products, nonsteroidal anti-inflammatory drugs, prostaglandins, colchicine, antineoplastics, antiarrhythmic drugs and cholinergic agents. Certain new drugs are likely to induce diarrhoea because of their pharmacodynamic properties; examples include anthraquinone-related agents, alpha-glucosidase inhibitors, lipase inhibitors and cholinesterase inhibitors. Antimicrobials are responsible for 25% of drug-induced diarrhoea. The disease spectrum of antimicrobial-associated diarrhoea ranges from benign diarrhoea to pseudomembranous colitis. Several pathophysiological mechanisms are involved in drug-induced diarrhoea: osmotic diarrhoea, secretory diarrhoea, shortened transit time, exudative diarrhoea and protein-losing enteropathy, and malabsorption or maldigestion of fat and carbohydrates. Often 2 or more mechanisms are present simultaneously. In clinical practice, 2 major types of diarrhoea are seen: acute diarrhoea, which usually appears during the first few days of treatment, and chronic diarrhoea, lasting more than 3 or 4 weeks and which can appear a long time after the start of drug therapy. Both can be severe and poorly tolerated. In a patient presenting with diarrhoea, the medical history is very important, especially the drug history, as it can suggest a diagnosis of drug-induced diarrhoea and thereby avoid multiple diagnostic tests. The clinical examination should cover severity criteria such as fever, rectal emission of blood and mucus, dehydration and bodyweight loss. Establishing a relationship between drug consumption and diarrhoea or colitis can be difficult when the time elapsed between the start of the drug and the onset of symptoms is long, sometimes up to several months or years.

Lactobacillus GG in the prevention of antibiotic-associated diarrhea in children

OBJECTIVE

The objective of this study was to determine the efficacy of Lactobacillus casei sps. rhamnosus (Lactobacillus GG) (LGG) in reducing the incidence of antibiotic-associated diarrhea when coadministered with an oral antibiotic in children with acute infectious disorders.

STUDY DESIGN

Two hundred two children between 6 months and 10 years of age were enrolled; 188 completed all phases of the protocol. LGG, 1 x 10(10) - 2 x 10(10) colony forming units per day, or comparable placebo was administered in a double-blind randomized trial to children receiving oral antibiotic therapy in an outpatient setting. The primary caregiver was questioned every 3 days regarding the incidence of gastrointestinal symptoms, predominantly stool frequency and consistency, through telephone contact by blinded investigators.

RESULTS

Twenty-five placebo-treated but only 7 LGG-treated patients had diarrhea as defined by liquid stools numbering 2 or greater per day. Lactobacillus GG overall significantly reduced stool frequency and increased stool consistency during antibiotic therapy by the tenth day compared with the placebo group.

CONCLUSION

Lactobacillus GG reduces the incidence of antibiotic-associated diarrhea in children treated with oral antibiotics for common childhood infections.

Evaluation of veterinary drug residues in food for their potential to affect human intestinal microflora

The use of veterinary drugs in food-producing animals may result in trace quantities of the drugs or their metabolites being present as residues in food. The effects of veterinary drugs intended for use in food-producing animals on intestinal microflora are evaluated in drug registration since these residues may pose a risk due to their antibiotic activity. This article reviews the different in vivo and in vitro experimental test systems and approaches used by animal health industries, contract laboratories, and regulatory authorities to assess the safety of veterinary drug residues in foods for human consumption. Furthermore, we propose a systematic approach to assess the effects and safety of veterinary drug residues on the human intestinal microflora.

In vitro fermentation of carbohydrate by breast fed and formula fed infants

Unabsorbed carbohydrates are fermented by colonic bacteria to short chain fatty acids (SCFA) which are rapidly absorbed, salvaging energy and reducing stool output. There are marked differences between the faecal flora and SCFA of breast fed (BF) and formula fed (FF) infants which may be related to the higher incidence of diarrhoea in FF infants. Part of this effect may be caused by a difference in the ability of the microflora to ferment carbohydrate. To test the hypothesis that BF and FF have different fermentation capacities for simple and complex carbohydrates, in vitro cultures of faeces from healthy infants (2-10 weeks; 11 BF, 11 FF) containing glucose, lactose, raftilose (a fructo-oligosaccharide), or soybean polysaccharide were incubated anaerobically. Results were compared with those of adult faecal cultures using the same carbohydrates. Cultures of faeces from BF and FF infants produced comparable amounts of total SCFA in all cultures. These cultures produced less SCFA than those from adult faeces and produced very little SCFA from complex carbohydrate. BF cultures produced more acetic acid than FF in all cultures, whereas FF cultures produced more propionate with sugars and more butyrate with raftilose. Both groups of infants produced less butyrate than adults in all cultures. Thus it is unlikely that a lower ability to ferment carbohydrate is a major cause of increased risk of diarrhoea in FF fed infants but individual SCFA production may be important.

Antibiotic-associated diarrhoea, Clostridium difficile, and short-chain fatty acids

BACKGROUND

It has been hypothesized that Clostridium difficile and decreased colonic production of short-chain fatty acids (SCFAs) cause the development of antibiotic-associated diarrhoea. We therefore wanted to investigate the effects of an intensive and uniform antibiotic therapy on faecal SCFAs concentrations. C. difficile, and extent of diarrhoea.

METHODS

Fifteen liver-transplanted patients who received oral bowel flora suppression therapy (6.3 g cefuroxime, 0.6 g tobramycin, and 0.5 g nystatin three times daily) were studied for 12 days before and 12 days after discontinuation of therapy.

RESULTS

Thirteen of the 15 patients (87%) developed diarrhoea. Colonic fermentation was negligible in all patients, judged by very low levels of faecal SCFAs (< 10 mmol/l). Diarrhoea lessened as suppression therapy proceeded despite continuous low levels of SCFAs. Initial stool frequency of 4.1 +/- 0.6 and viscosity of 2.5 +/- 0.2 per day (on a scale of 1-3; mean +/- SE) decreased to 2.2 +/- 0.5 (p = 0.0009) and 1.6 +/- 0.2 (p = 0.003) per day, respectively, just before cessation of suppression therapy. Both SCFAs and stool habits normalized within days after discontinuation of antibiotics. Only a few samples from 2 patients were culture-positive for C. difficile during therapy, whereas 9 of the 15 patients (60%) became culture-positive (6 cytotoxin-positive) after cessation of suppression therapy at a time when none had diarrhoea.

CONCLUSIONS

Intensive treatment with antibiotics directed against the colonic flora resulted in diarrhoea in the vast majority of patients, but the diarrhoea was self-limiting despite continual antibiotic treatment and very low faecal concentrations of SCFAs. C. difficile was not associated with antibiotic-associated diarrhoea but was a common finding after treatment with antibiotics was stopped at the time when diarrhoea had ceased.

Impact of polyunsaturated fatty acids on human colonic bacterial metabolism: an in vitro and in vivo study

Dietary polyunsaturated fatty acids (PUFA) reduce colonic proliferation and exert a mild laxative effect. We have studied the effect of the highly unsaturated eicosapentaenoic acid ethyl ester (EPA-EE) on the growth and metabolism of colonic bacteria in vitro, and in vivo. For the in vitro study, growth was assessed by viable counts. Bacteroides thetaiotaomicron was significantly inhibited in anaerobic media containing EPA-EE at concentrations > 7 milligrams. Escherichia coli was apparently resistant even at 100 milligrams. For the in vivo study, ten healthy volunteers ingested 18 g EPA-EE/d for 7 d. Stool frequency, 24 h stool weight and whole-gut transit time were assessed together with breath H2 and 14CO2 excretion following oral ingestion of 15 g lactitol labelled with 0.18 MBq [14C]lactitol. The area under the breath-H2-time curve was significantly reduced by EPA-EE, from a control value of 690.3 (SE 94.2) ppm.h to 449.5 (SE 91.7) ppm.h. Percentage dose of 14CO2 excreted, total stool weight and whole-gut transit time were unaltered, being respectively 24 (SE 2)%, 281 (SE 66) g and 45 (SE 4) h with EPA-EE v. control values of 27 (SE 1)%, 300 (SE 89) g and 42 (SE 5) h. It is concluded that dietary supplementation with EPA-EE reduces breath H2 excretion without apparently impairing overall colonic carbohydrate fermentation. The observed reduction may reflect utilization of H2 to hydrogenate the five double bonds of EPA-EE.

The effect of oral vancomycin on chronic idiopathic constipation

BACKGROUND

A case study reporting the efficacy of oral vancomycin in a patient with chronic idiopathic constipation prompted this prospective trial of oral vancomycin in eight female patients (aged 21-61 years) with severe constipation resistant to the action of dietary fibre.

METHODS

The trial was divided into two consecutive 14-day periods. During the first period, each patient was given ispaghula, 3.5 g twice a day, and during the subsequent period they took 250 mg vancomycin t.d.s. per os, as well as the fibre supplement. During both periods they collected stools and recorded daily bowel symptoms (stool frequency, straining, stool consistency, subjective stool volume) in a diary. At the end of each period whole gut transit time and the breath hydrogen response to a standard meal, giving oro-caecal transit time, were measured along with gastrointestinal symptoms which were assessed on visual analogue scales.

RESULTS

Vancomycin caused a significant improvement in stool frequency, consistency, ease of defecation and the amount of stool patients felt they produced (all P < 0.05), but objective measures of daily stool weight and whole gut or oro-caecal transit time were not significantly different. Basal breath hydrogen levels were higher after vancomycin treatment in seven out of eight patients. One patient experienced a complete remission of symptoms when she took vancomycin and remains in remission after 14 months. This patient showed no elevation in basal breath hydrogen level.

CONCLUSION

Although this study does not support the use of vancomycin for most patients with constipation, the results suggest that modification of the intraluminal flora may be of value in the treatment of the occasional case of idiopathic constipation.

Colonic fermentation: metabolic and clinical implications

Colonic SCFA formation from fermentable carbohydrate is important for the maintenance of morphologic and functional integrity of the colonic epithelium. Carbohydrate-induced diarrhea occurs when the amount of carbohydrate entering the colon exceeds its fermentation capacity. Deficient availability or utilization of SCFA, mainly of n-butyrate, is the cause of diversion colitis and may play important roles in colonic carcinogenesis, in starvation and enterotoxigenic diarrhea, and in idiopathic UC.

Colonic fermentation and nutritional recovery in rats with massive small bowel resection

BACKGROUND/AIMS

After massive small bowel resection, malabsorbed carbohydrates reach the colon and undergo fermentation. This study investigates the role of colonic fermentation in rats with 80% small bowel resection on weight gain, nitrogen balance, body composition, and intestinal adaptation.

METHODS

Resected or transected rats were fed a liquid diet enterally for 16 days with or without 30 mg/kg metronidazole to reduce fermentation. Weight gain was monitored until the rats were killed. Carcass composition, short-chain fatty acids in cecal content, total nitrogen output, and intestinal mucosal dry weight, protein, and DNA were measured.

RESULTS

Resected rats without metronidazole had a significantly better weight gain, carcass protein, nitrogen balance, and mucosal dry weight, protein, and DNA compared with that of resected rats receiving metronidazole. There were no significant differences between the two transected groups.

CONCLUSIONS

Decreasing colonic fermentation, measured by short-chain fatty acids in cecal content, reduced intestinal adaptation and nutritional recovery in rats with massive small bowel resection.

Pharmacology of dietary fibre

"Dietary fibre" includes a range of relatively poorly digested food substances mainly composed of non-starch polysaccharides. Pectins and gums are multi-branched hydrophilic substances, forming viscous solutions that delay gastric emptying and nutrient absorption from the small bowel. They are used to delay gastric emptying and improve glycemic control in diabetes, as well as to alleviate constipation. Other fibres, including cellulose and lignins, are insoluble and have little effect on gastric emptying and small bowel transit. They markedly accelerate colonic transit and are frequently used as laxatives. Other important, less well-characterised effects of fibre include lowering of blood cholesterol, increase in satiety and possibly reduction in colon neoplasia.

Diagnosis of hypolactasia and lactose malabsorption

The article briefly describes the various methods that are available for diagnosing hypolactasia. Special attention is drawn to the fact that different methods are useful at different levels of the health care organization. When the test result indicates lactose malabsorption, general malabsorption should be excluded by a glucose-galactose tolerance test, for example. If the glucose-galactose tolerance test produces a normal result, it can be assumed that the patient has primary adult-type selective lactose malabsorption. The possibility of secondary lactose malabsorption must be excluded according to the principles described by Villako & Maaroos (104).

Prevalence and consistency of low breath H2 excretion following lactulose ingestion. Possible implications for the clinical use of the H2 breath test

The clinical use of the H2 breath test is limited by the finding that a variable fraction of the population fails to excrete appreciable H2 during colonic carbohydrate fermentation. Therefore, we assessed the ability to increase breath H2 excretion in 371 patients (224 female, 147 male) by administering the nonabsorbable sugar lactulose. Following 12g of lactulose, 27% of 94 patients did not increase their breath H2 concentration over 20 ppm and were considered low H2 excretors. Ingestion of 20 g of lactulose in 277 patients yielded a frequency of low H2 excretors of 14%. Six of 10 patients that were low H2 excretors after 12g of lactulose increased their breath H2 levels over 20 ppm when tested with 20g. In 35 patients tested with the same amount of lactulose on two separate occasions, the subject frequently altered his or her H2 producing status over a period of a few weeks. Low H2 excretors had a significantly higher breath CH4 concentration, both fasting (22 +/- 34 ppm) and after lactulose (51 +/- 58 ppm) compared to the remaining patients (5 +/- 13 ppm and 16 +/- 40 ppm, respectively). While the mean age of low excretors (54 +/- 17 years) was significantly higher than the others (44 +/- 17 years), no difference was found for sex prevalence and stool pH. This study demonstrates that respiratory H2 excretion following lactulose ingestion is not consistent and suggests that the application of too restrictive criteria could lead to improper interpretation of the H2 breath test.

Shedding of Clostridium difficile, fecal beta-lactamase activity, and gastrointestinal symptoms in 51 volunteers treated with oral cefixime

Microbial changes including the shedding of Clostridium difficile, fecal beta-lactamase activity, and gastrointestinal symptoms were assessed in 51 healthy volunteers given 200 mg of cefixime twice daily for 8 days. The number of organisms of the family Enterobacteriaceae (means +/- standard deviations) dropped from 6.9 +/- 1.1 to 3.9 +/- 1.8 log CFU/g of feces (P < 0.01), whereas counts of enterococci rose from 7.0 +/- 1.5 to 9.0 +/- 1.0 log CFU/g of feces (P < 0.01). Both counts returned to their initial levels 50 days after the cessation of treatment. Cefixime did not significantly modify the frequency of fecal excretion of Pseudomonas aeruginosa, Staphylococcus spp., yeasts, or members of the Enterobacteriaceae resistant to ceftazidime or ampicillin. The proportion of subjects shedding C. difficile rose from 6% before treatment to 57% (P < 0.01) at the end of treatment but returned to 8% 50 days thereafter. No case of pseudomembranous colitis was observed. Stool changes occurred in 13 volunteers during treatment (25%) and in 2 others more than 10 days after the end of treatment (4%). These changes were not significantly associated with the shedding of toxigenic strains of C. difficile or with the presence of toxin A in feces. By contrast, during treatment, stool changes occurred in 8 of the 18 volunteers (44%) who had antibiotic activity in their feces but in only 5 of the 33 (15%) for whom no such activity was found (P < 0.05). The absence of antibiotic activity in the feces was itself linked with the presence of beta-lactamase activity in the feces. Since we had found earlier that fecal beta-lactamase activity afforded protection against alteration in stool consistency during treatments with oral cephalosporins, the present study confirmed our previous preliminary results in this respect.

Function of the human colon

Despite the volume of research on human colonic dysfunction, little is known about colonic function in health. This has stemmed partly from the difficulty in obtaining access to the organ. Two approaches have been used: studies on patients with stomas, and intestinal intubation techniques. The colonoscope has also recently been used to gain access. All these methods have limitations and results must be interpreted with caution. The accepted roles of the colon include the conservation of water and electrolytes and the controlled evacuation of faeces. Recent research has demonstrated its importance as a metabolic organ with an influence on overall metabolism, an effect that may in large part be attributed to the activity of colonic microflora. Evidence demonstrating that the defunctioned colon behaves differently from the functioning colon in the same individual has implications for a proper understanding of the organ, as practically all previous in vivo studies have been conducted in cleansed or defunctioned human colon.

Presence of Clostridium difficile and antibiotic and beta-lactamase activities in feces of volunteers treated with oral cefixime, oral cefpodoxime proxetil, or placebo

Three groups of six healthy adult volunteers were randomly assigned to a treatment with 400 mg of oral cefpodoxime proxetil, oral cefixime, or placebo per day for 10 days. Informed consent was obtained from all volunteers. Clostridium difficile was not detected in the feces of any subject before treatment or at any time in the subjects in the placebo group. C. difficile was, however, detected in all subjects treated with cefpodoxime proxetil and in five of six treated with cefixime. Genomic DNA restriction patterns showed that the strains of C. difficile differed from one volunteer to another. Two subjects both shed different strains at different times during the 25-day surveillance period. All isolates were resistant to cefixime and cefpodoxime (MIC for 90% of strains, 256 and 512 mg/liter, respectively). Antibiotic activity was found in the feces of one volunteer treated with cefpodoxime proxetil and of four volunteers treated with cefixime. It was inversely correlated with the presence of fecal beta-lactamase activity. Intestinal side effects were limited to modifications of stool consistency, which occurred in only 3 of the 12 treated volunteers and did not lead to cessation of treatment. These modifications were significantly associated with the presence of fecal antibiotic activity (P less than 0.05) but not with the shedding of toxigenic or nontoxigenic strains of C. difficile or with the presence of toxin A in feces, which was detected only in one perfectly healthy treated volunteer.

beta-Galactosidase from Aspergillus niger in adult lactose malabsorption: a double-blind crossover study

An assessment was made of the efficacy of a beta-galactosidase, obtained from Aspergillus niger and added to intact milk, in decreasing lactose malabsorption and intolerance. Sixteen adult patients with malabsorption and intolerance to this sugar were studied in a double-blind crossover study vs. placebo. A 5-hour hydrogen breath test was used to assess malabsorption of lactose contained in 400 ml milk. When compared with placebo, the addition of exogenous lactase to intact milk caused a statistically significant reduction in the maximum breath H2 concentration (P less than 0.01) and in the cumulative H2 excretion (P less than 0.005). In the same way, the cumulative index for gastrointestinal intolerance was significantly lower (P less than 0.005) after the ingestion of lactase-added milk. This study demonstrates that enzyme replacement therapy, with beta-galactosidases obtained from Aspergillus niger, is effective in decreasing lactose malabsorption and its consequent intolerance in adult subjects with lactase deficiency.

Alterations of intestinal microflora by antibiotics. Effects on fecal excretion, transit time, and colonic motility in rats

The effects of intragastric antibiotics in rats were examined on fecal microflora and excretion and through transit time and cecocolonic myoelectric activity. A solution of nonabsorbable antibiotics infused into the stomach for 20 days had a dramatic effect on the quantity, composition, and bacterial content of rat feces. Both the dry weight and the water content of feces were increased. The amount of short-chain fatty acids in the feces was dramatically lowered. However, neither total nor cecocolonic transit time of solids was affected. The cyclic organization of cecocolonic myoelectric activity was altered by antibiotic treatment, and the motility index, ie, the quantity of myoelectric activity recorded on the colon, progressively increased. An infusion of short-chain fatty acids modified this motor pattern but did not restore activity to a level comparable to that of control animals. In conclusion, intragastric antibiotics dramatically reduced intestinal microflora and increased fecal excretion of dry matter and water but did not affect the transit time of solid gut contents, although they did influence cecocolonic motility.

Colonic fermentation to short-chain fatty acids is decreased in antibiotic-associated diarrhea

To elucidate the pathogenesis of antibiotic-associated diarrhea, colonic carbohydrate fermentation was investigated in three groups of subjects--a group of controls, a group of patients with antibiotic-associated diarrhea, and a group of patients receiving antibiotic therapy without diarrhea. Compared with controls, the colonic fermentation was markedly impaired in patients with antibiotic-associated diarrhea reflected by both very low concentrations (22.1 vs. 59.5 mmol/L; P less than 0.01) and production rates of short-chain fatty acids. In the group of patients without diarrhea, the effect on the colonic fermentation was dependent on the antibiotic administered. Penicillin and pivampicillin PO did not reduce the concentrations (69.9 and 66.7 mmol/L, respectively) or production rates. Dicloxacillin, erythromycin, and combined IV treatment with ampicillin, netilmicin, and metronidazole reduced both concentrations (27.1, 38.2, and 18.8 mmol/L; P less than 0.01) and production rates of short-chain fatty acids to levels seen in patients with diarrhea. L-Lactate and D-lactate concentrations were normal in all patients (less than 5 mmol/L), but lactate production was reduced in the patients who had reduced production of short-chain fatty acids, including patients with diarrhea. Thus, antibiotic-associated diarrhea was always related to reduced fecal concentrations and production rates of short-chain fatty acids and production rates of lactate. These results suggest that the antibiotic-associated diarrhea might be secondary to impaired colonic fermentation in otherwise disposed subjects, resulting in accumulation of luminal carbohydrate and/or decreased short-chain fatty acid-stimulated sodium and water absorption.