Human Fecal Flora Research Articles

The prevalence of antimicrobial resistance in human faecal flora in South Africa.

Between January and March 1992, 361 faecal specimens were collected from the healthy black population in the Transvaal Province of South Africa. Each specimen was examined for the prevalence of antimicrobial resistance in commensal bacteria. Volunteers, from both rural and urban dwellings, were divided into four age groups. The overall carriage rate of resistance varied from 88.6% for ampicillin, 74.2% for trimethoprim, 52.6% for chloramphenicol, 10.2% for nalidixic acid to 7.5% for gentamicin. The carriage of resistance found to each individual antimicrobial agent was slightly higher in the rural population rather than the urban population but there was no correlation between the prevalence of antimicrobial resistance and the age group.

Characterization of human faecal flora by means of an improved fluoro-morphometrical method.

The use of polyclonal antibodies in differentiating between samples of faecal microflora derived from ten healthy volunteers was assessed. The distribution of FITC-labelled antibodies (of the IgA, IgG and IgM isotype) over 144 morphologically distinct subsets of faecal bacteria ('morphotypes') was quantified by means of digital morphometry and quantitative immunofluorescence. Furthermore, a new dataprocessing algorithm was developed which makes objective quantitation of the antibody distributions over the faecal morphotypes possible. The results of this study imply that the antibody binding capacity of faecal morphotypes is a unique characteristic of faecal microflora.

Rape-seed meal toxicity in gnotobiotic rats: influence of a whole human faecal flora or single human strains of Escherichia coli and Bacteroides vulgatus.

Gnotobiotic growing rats harbouring either a whole human faecal flora or single human strains of Escherichia coli (EM0) or Bacteroides vulgatus (BV8H1) were fed for 7 weeks on semi-synthetic diets in which the protein source was either soya-bean meal (SM) or rape-seed meal (RM). For each bacterial status the RM-diet group was compared with the control group fed on the SM diet. The association of human faecal flora with the RM diet was responsible for reduced feed intake and reduced weight gain, an enlargement of the liver and thyroid and a decrease in both thyroxine and triiodothyronine plasma levels. The association of the B. vulgatus BV8H1 strain with the RM diet reproduced all these effects, except that triiodothyronine plasma levels were not significantly modified. Rats inoculated with the E. coli EM0 strain and fed on the RM diet exhibited a goitre and lowered thyroxine and triiodothyronine plasma levels. These results show that the human intestinal microflora may be involved in glucosinolate metabolism when cruciferous vegetables are consumed by man. The specificity of the symptoms observed according to the rat bacterial status supports the hypothesis that bacteria yield specific toxic glucosinolate derivatives according to their enzymic potential.

Magnetic microcapsules as novel biomonitors of cross-linking agents and diet-dependent reactive oxygen species in the human gastrointestinal tract.

Six healthy, scientifically informed human volunteers were given 14C-labeled polyethyleneimine (PEI) microcapsules by mouth. Fecal 14C recovery was inversely related to mean gut transit time (r = -0.66), and the extent of cross-linking between the membrane and core PEI was inversely related to total fecal output (r = -0.81). Cross-linking of PEI microcapsules may be a biomonitor of endogenous cross-linking agents within the human gastrointestinal tract. Extensive loss of [14C]CH3 label occurred from the microcapsules during human transit and in in vitro fermentations with human fecal flora. A mechanism whereby reactive oxygen species could arise in the iron-rich core of these microcapsules, leading to loss of [14C]CH3 label, is proposed.

Effect of parenteral teicoplanin on human fecal flora

Effect of parenteral teicoplanin on human fecal flora

Factors affecting hydrogen production and consumption by human fecal flora. The critical roles of hydrogen tension and methanogenesis.

We studied the influence of hydrogen tension (PH2) and methanogenesis on H2 production and consumption by human fecal bacteria. Hydrogen consumption varied directly with PH2, and methanogenic feces consumed H2 far more rapidly than did nonmethanogenic feces. At low PH2, H2 production greatly exceeded consumption and there was negligible accumulation of the products of H2 catabolism, methane and sulfide. Thus, incubation at low PH2 allowed the first reported measurements of absolute as opposed to net H2 production. Feces incubated at high and intermediate PH2 had a net H2 production of only 1/900 and 1/64 of absolute production. Glucose fermentation by fecal bacteria yielded an absolute H2 production of 80 ml/g, a value far in excess of that excreted by volunteers ingesting lactulose. We conclude that most H2 produced by colonic bacteria is consumed and methanogenesis and fecal stirring (via its influence on fecal PH2) are critical determinants of H2 consumption and, hence, net H2 production. Study of fecal samples from four subjects with low breath H2 excretion after lactulose showed that absolute H2 production was normal, and the low H2 excretion apparently reflected increased consumption due to rapid methanogenesis (two subjects) and decreased luminal stirring (two subjects).

Effect of Lactobacillus acidophilus Supplements on Mutagen Excretion in Faeces and Urine in Humans

Lactic acid bacteria have been reported to have antimutagenic properties in vitro . In order to investigate whether Lactobacillus acidophilus supplements have antimutagenic effects in humans, 11 healthy subjects on a standardised diet consumed fried beef patties twice daily for 3 d. The diets were supplemented with ordinary Lactococcus fermented milk (phase 1) and thereafter with L. acidophilus fermented milk (phase 2), whereby the excretion of mutagenic activity was determined in urine and faeces. In both faeces and urine high levels of mutagenicity were detected during phase 1. There was an increase in lactobacilli in the intestinal microflora in seven of 11 subjects by the L. acidophilus supplement (phase 2), and the mutagenic activity in urine was 72 per cent lower on day 2 ( P < 0.01) and 55 per cent lower on day 3 ( P < 0.05) compared to days 2 and 3 in phase 1. The total faecal and urinary mutagen excretion on day 3 during phase 2 was 47 per cent lower compared to day 3, phase 1 ( P < 0.02). Thus, L. acidophilus given together with fried meat lowered mutagen excretion in humans. Keywords: Lactobacillus acidophilus ; Mutagens; Human faecal flora; Faeces; Urine.

Effect of Lactulose on the Composition and Metabolic Activity of the Human Faecal Flora

The effect of dietary supplementation with lactulose (3 g/d for 2 wk) on the faecal flora and faecal bacterial metabolism was studied in eight healthy volunteers. During the intake of lactulose, the number of bifidobacteria increased significantly ( P < 0.01), whereas the numbers of lecithinase-positive clostridia, including Clostridium perfringens , and Bacteroidaceae decreased ( P < 0.05) compared to values before and after the intake. Faecal indole, skatol and phenols, and faecal β-glucuronidase, nitroreductase and azoreductase activities were decreased significantly ( P < 0.05) after 7-14 d of treatment. Mean faecal pH decreased from 7.0 to 6.4, and water content increased 3.5-5.3 per cent during lactulose ingestion. Keywords: Lactulose; Faecal flora; Faecal bacterial metabolism.

Effect of Lactulose on the Composition and Metabolic Activity of the Human Faecal Flora

Effect of Lactulose on the Composition and Metabolic Activity of the Human Faecal Flora

Enhancing effects of bile salts on the degradation of glycosphingolipids by glycosidases from bacteria of the human fecal flora

Different concentrations of ionic and non-ionic detergents were examined for optimization of the in vitro degradations of intestinal glycosphingolipids by alpha- and beta-glycosidases from human fecal bacteria. In 5 mM Triton X-100 the enzymes hydrolyzed glycosphingolipids with lactoseries type 1 and 2 chains essentially to lactosylceramide (LacCer). In 5 mM sodium di- and trihydroxy bile salts lactosylceramide was degraded to glycosylceramide (GlcCer) in varying extent by enzymes from all five strains. The minimal bile salt concentrations for optimal 1,4-beta-galactosidase activities varied between 1 and 20 mM, i.e., close to or above the critical micellar concentrations (cmc). Dihydroxy bile salts were the most efficient in promoting conversion of LacCer to GlcCer at concentrations below 10 mM and conjugation with a taurine residue did not markedly lower the GlcCer yield. The optimal detergent concentrations for hydrolyses of the p-nitrophenyl (pnp) glycosides Gal beta 1-pnp and GalNAc alpha 1-pnp were approximately 0.05 mM for Triton X-100 and 0.5 mM for sodium taurodeoxycholate, i.e., clearly below their reported cmc values. Galabiosylceramide, globotria- and globotetraosylceramides, not degraded in the Triton X-100 micelles, were also resistant to hydrolysis using the sodium bile salts as detergents. In contrast, lactotetraosylceramide and isoglobotriaosylceramide were significantly more degraded by enzymes from a Ruminococcus gnavus strain and gangliotetraosylceramide by enzymes from a Bifidobacterium bifidum and a Bifidobacterium infantis strain using bile salt detergents. All strains but R. gnavus released terminal GalNAc from para-Forssman but not from the globotetraosylceramide or Forssman structures using 5 mM sodium deoxycholate as detergent. GM1 desialylation by two Ruminococcus torques strains and the R. gnavus and B. bifidum strains were enhanced under identical conditions. We conclude that the observed effects on glycosphingolipid hydrolyses reflects variations in the micellar presentation of the substrates. In addition, detergents seem to have a direct stimulating effect on the glycosidases, however at concentrations 10-100-times below the ones optimal for glycolipid degradations. These results with optimized bile salt concentrations, further support our previous observations that these five fecal bacterial strains produce enzymes with selected specificities towards glycosphingolipid core chains of the lactoseries type 1 and 2.

Development and Stability of Human Faecal Flora in the Intestine of Ex-germ-free Mice

Development of the faecal flora of ex-germ-free BALB/c mice inoculated with faecal dilutions of two healthy human adults was examined. Although the numbers of Enterobacteriaceae in the developing flora were high, compared with those in the faeces used for inoculation, during the first 2 d, they decreased markedly from the third day. Conversely, anaerobic bacteria were present in low concentrations on day 1 and increased thereafter. On day 3, anaerobic bacteria which were dominant in the human faeces became dominant in the ex-germ-free mice. The development of the faecal flora of these mice resembled that of neonatal animals and humans. Interestingly, bifidobacteria were eliminated from the ex-germ-free mice inoculated with faeces from one of the donors within 2-8 wk, while other bacteria remained constant. The elimination of bifidobacteria seemed to be dependent on the composition of flora of the inoculated sample. Ex-germ-free mice with a Bifidobacterium -free human faecal flora may provide a suitable animal model for studying their role in human health. Keywords: Faecal flora; Human flora; Mice; Germ-free; Bifidobacterium .

Effects of roxithromycin on fecal bacteria in human volunteers and resistance to colonization in gnotobiotic mice

The ecological impact of roxithromycin given orally at 300 mg/day on the intestinal floras in six human volunteers was studied. The resulting fecal concentrations of active roxithromycin were in the range of 100 to 200 micrograms/g of feces. Consecutive modifications in the composition of the fecal floras were limited to a decrease in counts of total members of the family Enterobacteriaceae. The rest of the intestinal floras, including the predominant anaerobic floras, changed little. No overgrowth of Pseudomonas aeruginosa, staphylococci, fungi, or highly erythromycin-resistant strains of the family Enterobacteriaceae was observed. The strains of Enterobacteriaceae and of anaerobes isolated during treatment were not markedly more resistant to roxithromycin than those isolated before treatment started. Changes in intestinal resistance to colonization by exogenous microorganisms in gnotobiotic mice inoculated with human fecal flora were studied and were also found to be minimal. The impact of oral roxithromycin on the intestinal microbiota appears to be weaker than that previously observed with oral erythromycin, perhaps because the concentrations of roxithromycin in the feces were lower than those previously found for erythromycin.

Effect of L-sorbose Intake on Human Fecal Flora and Production of Short-Chain Fatty Acids

Effect of L-sorbose Intake on Human Fecal Flora and Production of Short-Chain Fatty Acids

Development and Stability of Human Faecal Flora in the Intestine of Ex-germ-free Mice

Development and Stability of Human Faecal Flora in the Intestine of Ex-germ-free Mice

Effect of dietary fats on endogenous formation ofN‐nitrosamines from nitrate in germ‐free and conventional rats and rats harbouring a human flora

Urinary excretion of N-nitrosoproline (NPRO) was measured in groups of four germ-free (GF) and conventional (CV) rats given a purified diet with or without inclusion of 100 g butterfat, coconut oil or maize oil/kg, and drinking water containing 0.235 M-NaNO3. In the CV environment rats given the fat-supplemented diets excreted significantly less NPRO than those on the low-fat diet. No corresponding decrease in NPRO excretion occurred in the GF environment. Nitrate reductase activity was measured in stomach contents and homogenates of stomach tissue from GF and CV rats given the different diets. No activity was detected in any of the contents from GF rats. Nitrate reductase activity was significantly reduced in contents from all the CV rats given the fat-supplemented diets, the effect being most marked in those given butterfat. Activity was much lower in tissue homogenates from GF rats than in those from their CV counterparts, but was not affected by diet in either environment. Groups of four CV rats, or rats harbouring a human faecal flora (HF), were given the purified diet with or without addition of 100 g butterfat or maize oil/kg and drinking water containing 0.235 M-NaNO3. All groups given the fat-supplemented diet with the exception of the HF rats given butterfat. It is concluded that the reduced excretion of NPRO by rats given diets containing fat was mainly due to inhibition of microbial nitrate reductase activity in the foregut. The smaller effect of butterfat on the HF rats accords with earlier findings in human subjects.

Rapid Identification and Enumeration ofClostridium perfringensin the Human Faecal Flora

Lactose-sulphite broth was proposed initially for the rapid identification and enumeration of Clostridium perfringens in food but this medium can also be used for detection of the microorganism in raw material, in clinical specimens and in studies of human faecal flora. Its interpretation is simple and results are obtained within 24 h. Keywords: Clostridium perfringens ; Faeces; Faecal flora.

In vitro metabolism of catechol estrogens by human fecal microflora

Intestinal bacterial metabolism of the catechol estrogens, 2-hydroxyestrone (2-OHE1), 2-methoxyestrone (2-MeOE1) and 2-hydroxyestradiol (2-OHE2), was studied by incubation of the steroid with mixed fecal flora. 3-Methoxyestrone (3-MeOE1) was included in order to evaluate whether demethylation occurs also with regard to noncatecholic estrogens. The purification of the samples and separation into fractions was carried out by ion exchange chromatography and the metabolites formed were identified by combined gas chromatography-mass spectrometry (GC-MS). Mixed human fecal flora was able to interconvert 2-OHE1 and 2-OHE2 both in aerobic and anaerobic conditions. Demethylation occurred both for 2-MeOE1 and 3-MeOE1.

イソマルトオリゴ糖の機能特性とその応用

So-called isomalto-oligosaccharides are a mixture of isomaltose, panose, isomaltotriose, and anomalously linked oligosaccharides composed of four and five glucose units. Isomalt 500 is a commercial product of isomalto-oligosaccharides containing about 50 % of so-called isomaltooligosaccharides and has many favorable properties for application to food industry. It is mildly sweet, about half the degree of sweetness to sucrose in the same concentration, has high moisture-retaining capacity, low water activity convenient in controlling microbial contamination, is less f ermentable for yeast, and so on. Recently, we have investigated the effect of isomalto-oligosaccharides as a physiologically functional food ; one of them was the effect on human fecal flora, and another was the dental caries inhibitory effect. In this investigation, we used higher content containing about 90 % of so-called isomaltooligosaccharides named Isomalt 900 prepared by chromatographic separation from Isomalt 500. Isomalt 900 was utilized by Bifidobacteria classified as beneficial intestinal bacteria, but was not utilized by E. coli or most of Clostridium species which are unfavorable for humans in terms of both health and nutrition. After the administration of Isomalt 900 to humans, the numbers of Bifidobacteria in the feces increased and the consistency of feces was improved. On the other hand, the intake of sucrose-containing foodstuffs is related to the development of dental caries in humans. Several type of sweeteners have been developed as sucrose substitutes to prevent dental caries in humans. The effects of Isomalt 900 on glucan synthesis and sucrose-dependent cell adherence by St. mutans were investigated comparing it with these sucrose substitutes. Isomalt 900 effectively inhibited water-insoluble glucan synthesis from sucrose by glucosyltransf erase from St. mutans strains and sucrose-dependent adherence of various St. ntutans strains cell. These studies may support the usefulness of isomalto-oligosaccharides as components of new healthy foodstuffs. Many applications of isomalto-oligosaccharides in the food industry are now rapidly developing.

Steroid Metabolising Enzymes of Clostridia: A Characteristic for the Strain or the Species?

In recent years, strains of different Clostridia species capable of metabolising steroids have been isolated from human faecal flora and from sewage. The organisms (enzymes) are C. cadaveris (20β-reductase and C17-20 desmolase); C. sporogenes (C21-hydroxy-acetylase); C. paraputrificum (3α-hydroxy-5β-reductase, chemically known as hydroxy steroid dehydrogenase, HSDH) and C. innocuum (3β,5β-HSDH). Examination of type and stock culture strains from different sources demonstrated that synthesis of steroid metabolising enzymes was characteristic for the species. Of sixteen type/neotype strains not previously reported to synthesise steroid active enzymes, fourteen produced a C21 hydroxy acetylase, and two, C. glycolicum and C. carnis , a 3α, 5β-HSDH. Keywords: Clostridia; Enzymatic markers; Species specificity; Steroid metabolising enzymes.

The Role of Proteae in Diarrhea

A survey was undertaken on the occurrence of Proteae in the human fecal flora and its coincidence with other well-documented enteropathogens such as Campylobacter, Salmonella, Shigella, Staphylococcus aureus, Yersinia, protozoa and rotavirus. A total of 2000 fecal specimens was investigated, 1000 from patients suffering from diarrhea and 1000 from healthy persons which served as controls. Proteus mirabilis was isolated more frequently from diarrhea cases than from healthy people. The difference was statistically significant (P < 0.001). There was no correlation between its occurrence and isolation of Campylobacter, Salmonella, Shigella, Staphylococcus aureus, and protozoa. However, a questionable coincidence was found with rotavirus (P < 0.2) and a more certain correlation with Yersinia enterocolitica (P < 0.025). Proteus mirabilis in patients suffering from infection by other known enteropathogens was largely absent, suggesting that the organisms were independent causative agents of intestinal disorders. Notwithstanding this, they may additionally play a role as opportunists in enteric diseases due to some other pathogens.