Search

The microbiome has been identified to have a key role for the physiology of their human host. One of the major impacts is the clearance of bacterial pathogens. We have now developed a chemoselective probe methodology for the absolute quantification of short-chain fatty acids at low nM concentrations, with high reproducibility and spiked isotope labelled internal standards. Immobilization to magnetic beads allows for separation from the matrix and the tagged metabolites upon bioorthogonal cleavage can be analyzed via UHPLC-MS. The major advantage of our sensitive method is the simple combination with global metabolomics analysis as only a small sample volume is required.We have applied this chemical metabolomics strategy for targeted SCFA analysis combined with global metabolomics on gut microbiome co-cultures with Salmonella and investigated the effect of antibiotic treatment. [ABSTRACT FROM AUTHOR]

Gastrointestinal nitric oxide generation in germ-free and conventional rats. Am J Physiol Gastrointest Liver Physiol 287: G993-G997, 2004. First published July 15, 2004; doi:10.1152/ajpgi.00203.2004.--Nitric oxide (NO) is a central mediator of various physiological events in the gastrointestinal tract. The influence of the intestinal microflora for NO production in the gut is unknown. Bacteria could contribute to this production either by stimulating the mucosa to produce NO, or they could generate NO themselves. Using germ-free and conventional rats, we measured gaseous NO directly in the gastrointestinal tract and from the luminal contents using a chemiluminescence technique. Mucosal NO production was studied by using an NO synthase (NOS) inhibitor, and to evaluate microbial contribution to the NO generation, nitrate was given to the animals. In conventional rats, luminal NO differed profoundly along the gastrointestinal tract with the greatest concentrations in the stomach [>4,000 parts per billion (ppb)] and cecum ([approximately equal to] 200 ppb) and lower concentrations in the small intestine and colon ([less than or equal to] 20 ppb). Cecal NO correlated with the levels in incubated luminal contents. NOS inhibition lowered NO levels in the colon, without affecting NO in the stomach mad in the cecum. Gastric NO increased greatly after a nitrate load, proving it to be a substrate for NO generation. In germ-free rats, NO was low ([less than or equal to] 30 ppb) throughout the gastrointestinal tract and absent in the incubated luminal contents. NO also remained low after a nitrate load. Our results demonstrate a pivotal role of the intestinal microflora in gastrointestinal NO generation. Distinctly compartmentalized qualitative and quantitative NO levels in conventional and germ-free rats reflect complex host microbial cross talks, possibly making NO a regulator of the intestinal eco system. intestinal microflora; nitrate; nitrite; [N.sup.G]-nitro-L-arginine methyl ester; colitis

Background: Short-chain fatty acids (SCFAs) are abundant bacterial metabolites in the gut, with immunomodulatory properties. Hence, they may influence allergy development. Previous studies have linked fecal SCFA pattern during infancy with allergy. However, the association of SCFAs to allergic outcomes in adolescence is not well established. Here, we examined how the fecal SCFA pattern at 1 year of age related to allergy at 13 years of age. Methods: Levels of 8 SCFAs in fecal samples collected at 1 year of age from 110 children were quantified using gas chromatography. The same individuals were evaluated at 13 years of age for allergic symptoms, allergy diagnosis and allergy medication by questionnaire, and for sensitization using skin prick test against egg, milk, fish, wheat and soy, cat, dog, horse, birch, and timothy grass. Results: The concentration of fecal valeric acid at 1 year of age was inversely associated with eczema at 13 years of age (OR 0.6, 95% CI: 0.4–1.0, p = 0.049) and showed a trend for inverse association with food allergy at 13 years of age (OR 0.6, 95% CI: 0.4–1.0, p = 0.057). In a sub-group analysis of children with eczema at 1 year of age, a higher concentration of fecal valeric acid was linked with reduced risk of their eczema remaining at 13 years of age (OR 0.2, 95% CI: 0.0–1.5), although this latter analysis did not reach statistical significance (p = 0.12). Conclusions: Our findings lend further support to the notion of early childhood as a critical period when allergy may be programmed via the gut microbiota. Higher levels of fecal valeric acid may be characteristic of a protective gut microbiota and/or actively contribute to protection from eczema and food allergy. [ABSTRACT FROM AUTHOR]

A cross-sectional study was conducted to gain basic information on the fecal microbiota composition of different European study populations. Age-related differences in the microbiota makeup were detected but differed between the study populations from the four countries, France, Germany, Italy and Sweden, each showing a characteristic colonization pattern.

LINKED CONTENT: This article is linked to Størdal et al papers. To view these articles, visit https://doi.org/10.1111/apt.16361 and https://doi.org/10.1111/apt.16389 [ABSTRACT FROM AUTHOR]

Objective: To investigate—by molecular, classical and functional methods—the microbiota in biopsies and faeces from patients with active Crohn's disease (CD) and controls. Design: The microbiota in biopsies was investigated utilizing a novel molecular method and classical cultivation technology. Faecal samples were investigated by classical technology and four functional methods, reflecting alterations in short chain fatty acids pattern, conversion of cholesterol and bilirubin and inactivation of trypsin. Results: By molecular methods we found more than 92% similarity in the microbiota on the biopsies from the two groups. However, 4.6% of microbes found in controls were lacking in CD patients. Furthermore, NotI representation libraries demonstrate two different clusters representing CD patients and controls, respectively. Utilizing conventional technology, Bacteroides (alt. Parabacteroides) was less frequently detected in the biopsies from CD patients than from controls. A similar reduction in the number of Bacteroides was found in faecal samples. Bacteroides is the only group of bacteria known to be able to inactivate pancreatic trypsin. Faecal tryptic activity was high in CD patients, and inversely correlated to the levels of Bacteroides. Conclusions: CD patients have compositional and functional alterations in their intestinal microbiota, in line with the global description hypothesis rather than the candidate microorganism theory. The most striking functional difference was high amount of faecal tryptic activity in CD patients, inversely correlated to the levels of Bacteroides in faeces. [ABSTRACT FROM AUTHOR]

Objective: Recent work indicates that the gut microflora is altered in patients with coeliac disease (CD). Faecal short-chain fatty acids (SCFAs) are produced by the gut microflora. We have previously reported a high SCFA output in children with symptomatic and asymptomatic CD at presentation, as well as in CD children on a gluten-free diet (GFD) for less than 1 year, indicating deviant gut microfloral function. In this report, we focus on faecal SCFA production in coeliacs on GFD for more than 1 year. Materials and methods: Faecal samples were collected from 53 children with CD at presentation, 74 coeliac children on GFD for less than 1 year, and 25 individuals diagnosed with CD in childhood and on GFD for more than 1 year. The control group comprised 54 healthy children (HC). The faecal samples were analysed to show the SCFA pattern taken as a marker of gut microflora function. We applied a new fermentation index, reflecting the inflammatory activity of the SCFAs (amount of acetic acid minus propionic acid and n-butyric acid, together divided by the total amount of SCFAs). Results: In coeliacs on GFD for more than 1 year, the individual SCFAs, total SCFA, and fermentation index did not differ significantly from the findings in controls. In contrast, the faecal SCFA level was clearly higher in coeliacs treated with GFD for less than 1 year compared to those more than 1 year. Conclusions: This is the first study on SCFA patterns in faecal samples from individuals with CD on GFD for more than 1 year. Our study indicates that the disturbed gut microflora function in children with CD at presentation and after less than 1 year of GFD, previously demonstrated by us, is normalised on GFD for more than 1 year. [ABSTRACT FROM AUTHOR]

Objective. Exclusive enteral nutrition (EEN) is a first-line treatment in children with active Crohn's disease (CD) but is seldom used in adults with active disease. The mode of action of EEN in suppressing mucosal inflammation is not fully understood, but modulation of intestinal microflora activity is one possible explanation. The aim of this study was to investigate the effect of 6-week EEN in children with active CD, with special reference to intestinal microflora function. Materials and methods. Fecal samples from 18 children (11 boys, 7 girls; median age 13.5 years) with active CD (13 children with small bowel/colonic and 5 with perianal disease) were analyzed for short chain fatty acid (SCFA) pattern as marker of gut microflora function. The children were studied before and after EEN treatment. Results from 12 healthy teenagers were used for comparison. Results. Eleven (79%) of the children with small bowel/colonic CD responded clinically positively to EEN treatment showing decreased levels of pro-inflammatory acetic acid as well as increased concentrations of anti-inflammatory butyric acids and also of valeric acids, similar to the levels in healthy age-matched children. In children with active perianal CD, however, EEN had no positive effect on clinical status or inflammatory parameters. Conclusions. The authors present new data supporting the hypothesis that the well-documented anti-inflammatory effect of EEN in children with active small bowel/colonic CD is brought about by modulation of gut microflora activity, resulting in an anti-inflammatory SCFA pattern. By contrast, none of the children with perianal disease showed clinical or biochemical improvement after EEN treatment. [ABSTRACT FROM AUTHOR]

Clostridium difficile-associated disease (CDAD) with frequent watery stools, sometimes with painful bowel movements, fever and sickness, is probably the major known cause of antibiotic-associated diarrhea and colitis, most probably depending on a disruption of the normal intestinal balance in the microbiome. In this study, we have inoculated a mixture of fecal microbes - as an enema - originating from a healthy Scandinavian middle-aged donor, regularly re-cultivated under strict anaerobic conditions for more than 10 years, to 32 patients. Twenty-two patients (69%) were durably cured. In those patients receiving the transplant by colonoscopy, four out of five were cured. To the best of our knowledge, this is the first time a fecal culture of microbes has retained the possibility for years to cure a substantial number of patients with CDAD. [ABSTRACT FROM AUTHOR]

Objective. The aim of this study was to investigate the metabolic function of intestinal microflora in children with screening-detected celiac disease (CD) to see if there is an aberrant gut flora in screening-detected CD similar to symptomatic CD and contrary to healthy controls. Materials and methods. As part of a Swedish multicenter screening for CD, 912 12-year-old children were screened with serum anti-human tissue transglutaminase-IgA. Small bowel biopsy specimens from children with positive serology revealed 17 individuals with CD. The functional status of the intestinal microflora was evaluated by gas–liquid chromatography of short chain fatty acids (SCFAs) in fecal samples. Our previously published findings in children with symptomatic CD and healthy controls were used as comparison. Results. The children with screening-detected CD had a similar fecal SCFA profile to children with symptomatic CD, but differed significantly from that in healthy children. Conclusions. This is the first study on SCFA patterns in fecal samples from children with screening-detected CD. The similarity of the fecal SCFA profile in screening-detected and symptomatic CD indicates common pathogenic mechanisms. This could open the way for new therapeutic or prophylactic measures based on novel biological principles. [ABSTRACT FROM AUTHOR]

Purpose: Enterometabolic disturbances may cause meal-related symptoms. We performed a functional evaluation of the intestinal microflora in patients with unexplained, self-reported food hypersensitivity by measuring fecal short-chain fatty acids (SCFAs). Patients and methods: Thirty-five consecutive patients with self-reported food hypersensitivity and 15 healthy volunteers of similar age, gender, and body mass index collected all feces for 72 hours. Fecal concentrations of acetic, propionic, n-butyric, i-butyric, n-valeric, i-valeric, n-caproic, and i-caproic acids were analyzed by gas-liquid chromatography. Concentrations and excretions (output) of SCFAs in patients and controls were compared and related to gastrointestinal symptoms. Results: Despite nonsignificant differences between patients and controls for both total and individual SCFA concentrations and excretions, n-butyric acid comprised a higher (P = 0.035) and acetic acid a lower (P = 0.012) proportion of total SCFA in patients compared to controls. There were no significant correlations between symptom scores and concentrations or excretions of individual or total SCFAs, but the proportion of n-butyric acid was significantly higher in patients with severe symptoms compared to patients with moderate symptoms (P = 0.016). Conclusion: The results indicate an enterometabolic disturbance in patients with self-reported food hypersensitivity. Higher proportions of n-butyric acid may be related to abdominal symptom generation, but may also protect against organic bowel disease. Further studies are needed to clarify these aspects. [ABSTRACT FROM AUTHOR]

Objective. Malabsorption of low-digestible carbohydrates is physiological, but poorly tolerated in some patients. We investigated symptom anticipation and microbial fermentation as possible mechanisms of carbohydrate intolerance in patients with self-reported food hypersensitivity. Material and methods. In a randomized, double-blind, cross-over study, 27 consecutive patients with unexplained, self-reported food hypersensitivity were given 10 g lactulose and 10 g glucose (placebo). Symptoms and pulmonary excretion of hydrogen and methane were assessed. Short-chain fatty acids (SCFAs), lactate and prostaglandin E2 (PGE2) were analyzed in rectal dialysis fluid, and compared to dialysates from nine healthy volunteers. Results. Post-lactulose symptom scores were correlated with habitual symptom scores ( r = 0.6, p = 0.001), significantly higher than post-glucose symptom scores ( p = 0.01) and significantly higher in patients than controls ( p = 0.0007). Levels of SCFAs, lactate and PGE2 in rectal dialysates were not significantly different after lactulose and glucose, or between patients and controls. Hydrogen excretion was not correlated with symptom scores. Conclusions. The findings suggest that self-reported food hypersensitivity is related to microbial fermentation of malabsorbed carbohydrates and not to symptom anticipation solely. Levels of SCFAs, lactate and PGE2 in rectal dialysates could not explain the fermentation-associated hypersensitivity. [ABSTRACT FROM AUTHOR]

Objective. Intestinal infection with Giardia lamblia may lead to therapy-resistant, long-lasting post-giardiasis irritable bowel syndrome (IBS). We report two open pilot studies aiming to treat this condition, using either antibiotics or bacterio-therapy. Material and methods. Twenty-eight patients with persistent abdominal symptoms, following clearance of G. lamblia infection, were investigated. Eighteen received treatment with rifaximin plus metronidazole (8--10 days) whereas 10 received a suspension of live faecal flora, installed into the duodenum during gastro-duodenoscopy. Customary abdominal symptoms and symptoms following a lactulose breath test were quantified by questionnaires. Hydrogen and methane production after lactulose were analysed in expired air and excretion of fat and short-chain fatty acids (SCFAs) was examined in faeces. Results. As compared with pre-treatment values, total customary symptom scores were barely significantly reduced ( p == 0.07) after antibiotics, but were highly significantly reduced ( p == 0.0009) after bacterio-therapy. However, symptom improvement following bacterio-therapy did not persist 1 year later. Hydrogen breath excretion was slightly reduced after antibiotics, but not after bacterio-therapy. Compared with healthy persons, faecal excretion of fat was significantly increased in Giardia-cured patients. SCFAs were increased in the bacterio-therapy group, and were not influenced by therapy. Conclusions. Both antibiotics and bacterio-therapy were ineffective with respect to cure of post-giardiasis IBS. High faecal excretion of fat and SCFAs suggests that intestinal malabsorption of fat and carbohydrates may play a role in the IBS-like complaints of these patients. [ABSTRACT FROM AUTHOR]

The article focuses on the factors that contribute to the growth and development of breastfed and non-breastfed infants considering the specifications of the Growth Chart Standards of the World Health Organization (WHO). It states that the Growth Chart Standards are used to determine the growth rate of breastfed infants on their first six months. It adds that the fat intake of the mother affects the contents of her milk which pose consequences for the offspring. It also suggests that mammary glands in may have developed from skin glands responsible for immunity. Moreover, it highlights biological compounds that affect infant growth including human lactoferrin, milk oligosaccharides and anti-secretory factors (AF).

Objective. In celiac disease (CD), enteropathy of the small bowel results from a T-cell-mediated reaction to gluten in the diet. In addition to gluten, other environmental and genetic factors participate in the disease pathogenesis. We have recently reported the finding of a significantly different short-chain fatty acid (SCFA) profile in fecal samples from children with CD compared to healthy controls reflecting an aberrant gut microflora. The aim of the present study was to make a functional evaluation of the gut microflora status in non-celiac 1st degree relatives of children with CD. Material and methods. Fecal samples from 76 symptom-free, non-celiac, 1st degree CD relatives and from 91 aged-matched healthy controls were analyzed for fecal tryptic activity (FTA) and a number of SCFAs. Results. There was a significantly lower level of acetic acid and total SCFAs as well as a significantly increased level of i-butyric acid and FTA in relatives compared to healthy controls. Conclusions. The FTA and the SCFA profiles in fecal samples from 1st degree relatives of children with CD are different from those of healthy individuals. The implication of this observation provides insight into the pathogenesis of CD and opens up the possibility of future new diagnostic, therapeutic and prophylactic strategies. [ABSTRACT FROM AUTHOR]

Fecal water (FW) has been shown to exert, in cultured cells, cytotoxic and genotoxic effects that have implications for colorectal cancer (CRC) risk. We have investigated a further biological activity of FW, namely, the ability to affect gap junctions in CACO2 cell monolayers as an index of mucosal barrier function, which is known to be disrupted in cancer. FW samples from healthy, free-living, European subjects that were divided into two broad age groups, adult (40 ± 9.7 yr; n = 53) and elderly (76 ± 7.5 yr; n = 55) were tested for effects on gap junction using the transepithelial resistance (TER) assay. Overall, treatment of CACO2 cells with FW samples from adults increased TER (+ 4%), whereas FW from elderly subjects decreased TER (- 5%); the difference between the two groups was significant (P < 0.05). We also measured several components of FW potentially associated with modulation of TER, namely, short-chain fatty acid (SCFA) and ammonia. SCFAs (propionic, acetic, and n-butyric) were significantly lower in the elderly population ( - 30%, - 35%, and - 21%, respectively, all P £ 0.01). We consider that FW modulation of in vitro epithelial barrier function is a potentially useful noninvasive biomarker, but it requires further validation to establish its relationship to CRC risk. [ABSTRACT FROM AUTHOR]

The establishment of β-glucuronidase activity was investigated in intestinal contents from gnotobiotic mice monoassociated either with Lactobacillus rhamnosus ATCC 53103 (LGG) or with Escherichia coli X7 for different periods of time. Additionally, the enzyme activity was investigated after the animals had been conventionalized. Neither the monoassociated animals nor the conventionalized animals had reached normal levels of β-glucuronidase activity after the colonization period (3 and 7 days, or 7 and 14 days, respectively). A great inter-individual variation of the enzyme activity was observed in the group that was conventionalized for longer (14 days), mainly in the caecum. These results indicate a very slow establishment of the β-glucuronidase activity in the intestinal tract of mice after exposure to either individual bacterial strains or exclusively to the environment. [ABSTRACT FROM AUTHOR]

Intestinal cholesterol can be absorbed by the host or converted by the intestinal microbiota. The main metabolite of cholesterol conversion is coprostanol, which is unabsorbable. The aim of the present study was to examine the intestinal microbial conversion of cholesterol to coprostanol in healthy subjects. Cholesterol and coprostanol were determined in faecal samples from individuals living in Norway, Scotland and Sweden and examined for possible relationship to age ( 50 years old) and gender. The results were expressed as the percentage of coprostanol in the total amount of cholesterol plus coprostanol (coprostanol%). For purposes of classification, subjects were divided in non-converters ( p p [ABSTRACT FROM AUTHOR]

It is generally accepted that gastrointestinal short-chain fatty acids (SCFAs) – acetic, propionic and butyric acid – are mostly derived from carbohydrates, while iso-butyric and iso-valeric acids are from protein sources. We have investigated the faecal SCFAs and the correlation between the branched-chain fatty acids iso-butyric and iso-valeric in humans, rats, horses and pigs. The subjects were of different ages, fed on different diets and housed in different environments. High differences in the total output of SCFAs were observed within and between species. Despite these differences, a remarkable correlation between the iso-butyric and the iso-valeric acids was found. The fact that the correlation is strong irrespective of species, age, diet and living conditions indicates a common source actually reaching the hindgut. We hypothesize that this source is intestinal sloughed cells. [ABSTRACT FROM AUTHOR]

The prevalence of immunologically mediated diseases including allergies in Western countries has increased significantly during the past 3050 years, in contrast to what has happened in the former socialist countries. An altered intestinal microbial stimulation may be one reason for a changed immune response. One possible explanation is that there could be quantitative and/or qualitative differences between the establishment of a functionally active intestinal microflora in infants in Western countries leading to different maturation of the enterocytes. The aim of this study was to investigate the function of the metabolically active intestinal microflora in cohorts of 43 healthy infants from Estonia and 25 healthy infants from Sweden during their first year of life by studying the short-chain fatty acid (SCFA) profile in faecal samples. The SCFA profiles differ significantly during the first month of life. At 1 month of age, the Swedish infants have significantly higher amounts of SCFAs in their faeces, and all acids except iso-butyric acid were present in more Swedish than Estonian infants. Moreover, there was a quicker 'shift to the right' with regard to the presence of the higher acids (C4-C6) in the Swedish infants. Our results show significant differences in a major microbial intestinal function between Estonian and Swedish infants during their first month of life. Possible causes for these findings and the impact on the host of the diverse SCFA profiles is discussed. These findings have created a background for ongoing studies on allergy and atopy in infants. [ABSTRACT FROM AUTHOR]

The gastrointestinal tract of all animals is colonized with a vast, complex and dynamic consortium of microorganisms. In spite of recent progress in molecular microbiology, this complexity makes a proper qualitative and quantitative evaluation difficult and expensive to perform. In the present review we discuss the results obtained from applying a functional concept for studying intestinal host-microbial interactions in eight mammalian species and two species of fish. We show that microbial interactions with endogenous derived substrates such as cholesterol, bilirubin, mucin and trypsin occur in all species. Exogenous compounds (e.g. carbohydrate, protein, fibre) are also acted upon by the intestinal microflora. From an evolutionary point of view, dietary differences have led to a compartmentalized variability in microbial functions. Taken together, the results in this review underscore the importance of understanding precisely how gastrointestinal metabolism serves to establish a symbiotic cross-talk between animals and their gastrointestinal flora. [ABSTRACT FROM AUTHOR]

3-Hydroxy fatty acids (3-OH FAs) of 10–18-carbon chain lengths are constituents of the lipopolysaccharide of Gram-negative bacteria. These acids are used as chemical markers for determining endotoxin in environmental samples. The present communication addresses the question whether this type of analysis also would be applicable to mammalian samples. Low levels (6.1±1.6–94.0±23.2 pmol/ml) of the studied 3-OH FAs were detected in blood from both conventional and germ-free rats. The levels were considerably higher (0.0–1.06±0.17 nmol/mg) in livers. The amounts of the 3-OH FAs did not differ between the two groups of rats. All analyses were made by gas chromatography–tandem mass spectrometry (GC–MSMS) for unequivocal identification. The results illustrate a limitation in using 3-OH FA analysis to determine endotoxin in mammalian samples since these acids may represent not only endotoxin but also products from mammalian mitochondrial fatty acid β-oxidation. [Copyright &y& Elsevier]

Background: Several bacterial strains, mainly those belonging to the genera Lactobacillus, Enterococcus, Streptococcus and Bifidobacterium, are currently used as probiotics. Objective: The aim of this study was to investigate the influence of probiotics on five biochemical microbial-related functions in vitro and in vivo, in gnotobiotic mice, by applying the GAC/M AC (germ-free animal characteristic/microflora-associated characteristic) concept. Design: Sixteen probiotics were monoinoculated in vitro and/or monoassociated to germ-free mice to investigate the following biochemical parameters in large intestinal samples: inactivation of tryptic activity, degradation of β-aspartylglycine and of mucin, conversion of bilirubin to urobilinogen and β-glucuronidase activity. Results: Lactobacillus reuteri 2010, L. rhamnosus strain 271, L. rhamnosus ATCC7469 and L. rhamnosus GG ATCC53103 expressed β-glucuronidase activity. The other parameters tested were not influenced by any of the probiotics. Conclusions: Bacterial β-glucuronidases have an important intestinal function. As many microbial-host and microbe-diet interactions occur in the gastrointestinal tract of mammals, microbial-related functions should be studied in greater detail in probiotics. [ABSTRACT FROM AUTHOR]

This chapter will summarise the role of some functionally active intestinal microbes acting on man and animal on some anatomical, physiological and biochemical functions. The influences on immunological functions will be presented separately. The baselines for these functions refer to studies performed in material from germfree animals and healthy newborns, and values obtained are compared to functions in a macro-organism which have been in affected by a micro-flora. In principle, these functions are similar in all the organisms so far investigated, only the levels vary, due to age, and different dietary components and environmental factors. Alterations of the normal pattern of these functions mainly reflects altered ecological conditions in the organism and the reasons for these are sometimes known-sometimes unknown. The consequences after alterations of these functions have to be investigated in several ways, i.e., both with regard to local and distal effects on the host organism. [ABSTRACT FROM AUTHOR]

Abstract: For many years, laboratory animal breeders have used a mixture of eight bacterial strains, the so-called Altered Schaedler Flora (ASF) to inoculate Caesarian derived offspring when establishing colonies of Specific Pathogen Free (SPF) rodents fulfilling the criteria worked out by regulatory agencies as AALAS, FELASA, etc. However, recently it was shown in this journal that such SPF animals harbored a fecal flora far different from that of feral mice. Over the years, we have worked with functional aspects of host-microbe interactions(s) and the aim of the present study was to analyze some intestinal microbial biochemical activities in mice harboring an ASF flora. In the five parameter studied, the ASF mice showed a pattern similar to what is found in germfree mice and rats, demonstrating an absence of microorganisms capable of performing these reactions. These findings call for a re-considering of the SPF concept. Presence of important microbiological functions should be taken into consideration when rodents are used in biomedical research. [Copyright &y& Elsevier]

A letter to the editor is presented in response to the article "Guidelines for diagnosis, treatment, and prevention of Clostriduim difficile infections" by C. Surawicz and colleagues in a previous issue of 2013.