Studies of stools from pseudomembranous colitis, rotaviral, and other diarrheal syndromes by frequency-pulsed electron capture gas-liquid chromatography

Biogenic amine tryptamine in human vaginal probiotic isolates mediates matrix inhibition and thwarts uropathogenic E. coli biofilm

Probiotics offer a promising prophylactic approach against various pathogens and represent an alternative strategy to combat biofilm-related infections. In this study, we isolated vaginal commensal microbiota from 54 healthy Indian women to investigate their probiotic traits. We primarily explored the ability of cell-free supernatant (CFS) from Lactobacilli to prevent Uropathogenic Escherichia coli (UPEC) colonization and biofilm formation. Our findings revealed that CFS effectively reduced UPEC's swimming and swarming motility, decreased cell surface hydrophobicity, and hindered matrix production by downregulating specific genes (fimA, fimH, papG, and csgA). Subsequent GC-MS analysis identified Tryptamine, a monoamine compound, as the potent bioactive substance from Lactobacilli CFS, inhibiting UPEC biofilms with an MBIC of 4 µg/ml and an MBEC of 8 µg/ml. Tryptamine induced significant changes in E. coli colony biofilm morphology, transitioning from the Red, Dry, and Rough (RDAR) to the Smooth and White phenotype, indicating reduced extracellular matrix production. Biofilm time-kill assays demonstrated a four-log reduction in UPEC viability when treated with Tryptamine, highlighting its potent antibacterial properties, comparable to CFS treatment. Biofilm ROS assays indicated a significant elevation in ROS generation within UPEC biofilms, suggesting a potential antibacterial mechanism. Gene expression studies with Tryptamine-treated samples showed a reduction in expression of curli gene (csgA), consistent with CFS treatment. This study underscores the potential of Tryptamine from probiotic Lactobacilli CFS as a promising antibiofilm agent against UPEC biofilms.

Gut Microbiota-Produced Tryptamine Activates an Epithelial G-Protein-Coupled Receptor to Increase Colonic Secretion

Tryptamine, a tryptophan-derived monoamine similar to 5-hydroxytryptamine (5-HT), is produced by gut bacteria and is abundant in human and rodent feces. However, the physiologic effect of tryptamine in the gastrointestinal (GI) tract remains unknown. Here, we show that the biological effects of tryptamine are mediated through the 5-HT₄ receptor (5-HT₄R), a G-protein-coupled receptor (GPCR) uniquely expressed in the colonic epithelium. Tryptamine increases both ionic flux across the colonic epithelium and fluid secretion in colonoids from germ-free (GF) and humanized (ex-GF colonized with human stool) mice, consistent with increased intestinal secretion. The secretory effect of tryptamine is dependent on 5-HT₄R activation and is blocked by 5-HT₄R antagonist and absent in 5-HT₄R^-/- mice. GF mice colonized by Bacteroides thetaiotaomicron engineered to produce tryptamine exhibit accelerated GI transit. Our study demonstrates an aspect of host physiology under control of a bacterial metabolite that can be exploited as a therapeutic modality. VIDEO ABSTRACT.

Deciphering Human Gut Microbiota-Nutrient Interactions: A Role for Biochemistry

The human gut contains trillions of microorganisms that play a central role in many aspects of host biology, including the provision of key nutrients from the diet. However, our appreciation of how gut microbes and their extensive metabolic capabilities affect the nutritional status of the human host is in its infancy. In this Perspective, we highlight how recent efforts to elucidate the biochemical basis for gut microbial metabolism of dietary components are reshaping our view of these organisms' roles in host nutrition. Gaining a molecular understanding of gut microbe-nutrient interactions will enhance our knowledge of how diet affects host health and disease, ultimately enabling personalized nutrition and therapeutics.

Discovery and characterization of gut microbiota decarboxylases that can produce the neurotransmitter tryptamine

Several recent studies describe the influence of the gut microbiota on host brain and behavior. However, the mechanisms responsible for microbiota-nervous system interactions are largely unknown. Using a combination of genetics, biochemistry, and crystallography, we identify and characterize two phylogenetically distinct enzymes found in the human microbiome that decarboxylate tryptophan to form the β-arylamine neurotransmitter tryptamine. Although this enzymatic activity is exceedingly rare among bacteria more broadly, analysis of the Human Microbiome Project data demonstrate that at least 10% of the human population harbors at least one bacterium encoding a tryptophan decarboxylase in their gut community. Our results uncover a previously unrecognized enzymatic activity that can give rise to host-modulatory compounds and suggests a potential direct mechanism by which gut microbiota can influence host physiology, including behavior.

Synbiotic Lactobacillus acidophilus NCFM and cellobiose does not affect human gut bacterial diversity but increases abundance of lactobacilli, bifidobacteria and branched-chain fatty acids: a randomized, double-blinded cross-over trial

Probiotics, prebiotics, and combinations thereof, that is synbiotics, have been reported to modulate gut microbiota of humans. In this study, effects of a novel synbiotic on the composition and metabolic activity of human gut microbiota were investigated. Healthy volunteers (n = 18) were enrolled in a double-blinded, randomized, and placebo-controlled cross-over study and received synbiotic [Lactobacillus acidophilus NCFM (10(9) CFU) and cellobiose (5 g)] or placebo daily for 3 weeks. Fecal samples were collected and lactobacilli numbers were quantified by qPCR. Furthermore, 454 tag-encoded amplicon pyrosequencing was used to monitor the effect of synbiotic on the composition of the microbiota. The synbiotic increased levels of Lactobacillus spp. and relative abundances of the genera Bifidobacterium, Collinsella, and Eubacterium while the genus Dialister was decreased (P < 0.05). No other effects were found on microbiota composition. Remarkably, however, the synbiotic increased concentrations of branched-chain fatty acids, measured by gas chromatography, while short-chain fatty acids were not affected.

Rapid diagnosis of tuberculous meningitis by frequency-pulsed electron-capture gas-liquid chromatography detection of carboxylic acids in cerebrospinal fluid

The frequency-pulsed electron-capture gas-liquid chromatography technique described previously by Brooks et al. was modified and applied to the studies of coded and routine clinical specimens. Uncentrifuged cerebrospinal fluid (2 ml) was extracted under acidic conditions, derivatized, and analyzed by frequency-pulsed electron-capture gas-liquid chromatography on large-bore fused silica polar and nonpolar capillary columns. The frequency-pulsed electron-capture gas-liquid chromatography profile of carboxylic acids (C2 through C22) along with identification of tuberculostearic acid, established by retention time comparison of derivatized tuberculostearic acid and derivatized sample extract, strongly suggests the presence of Mycobacterium tuberculosis in patients with lymphocytic meningitis. Results from 41 coded cases and 75 clinical cases showed that the frequency-pulsed electron-capture gas-liquid chromatography test had a specificity of 91% and a sensitivity of 95%.

Studies of metabolites in diarrheal stool specimens positive for Klebsiella, Serratia, and Proteus spp. by frequency-pulsed electron-capture gas chromatography

Diarrheal stools from infants from which Klebsiella pneumoniae, Serratia liquefaciens, and Proteus mirabilis were isolated as possible causative agents of diarrhea were studied. These stools, along with control stool specimens which were collected from infants in the same village of Tamooh (near Cairo, Egypt), were analyzed by frequency-pulsed electron-capture gas chromatography (FPEC-GC). Watery stools and formed stools, to which distilled water was added, were centrifuged, and the supernatant was extracted with organic solvents and derivatized with specific functional group reagents to form electron-absorbing derivatives of carboxylic acids, hydroxy acids, alcohols, and amines. Results from the study showed distinct differences in FPEC-GC profiles of stools positive for K. pneumoniae, S. liquefaciens, and P. mirabilis. The major differences found were that diarrheal stools from which K. pneumoniae was isolated contained acetoin, a hydroxy acid-labeled peak F, and an unidentified amine, peak A. S. liquefaciens diarrheal stools had FPEC-GC profiles like the controls with the exception that an amine, peak A, was detected. The diarrhel stools containing P. mirabilis produced a distinct amine profile.

Laboratory diagnosis of Clostridium difficile-associated diarrhoea

This paper reviews the various laboratory procedures available for the isolation and identification of Clostridium difficile and the detection of toxins produced by this organism. Laboratories should be selective in determining which patients require investigation for Clostridium difficile-associated diarrhoea. Transport and storage of stool specimens at 4 degrees C is recommended when delays in processing may occur. Tissue culture techniques are still the best method for detection of cytotoxin and a variety of cell lines can be used. Other methods for detecting cytotoxin, and methods for detecting other toxins are not sufficiently developed yet to warrant introduction into diagnostic laboratories. Culture techniques remain the most sensitive for diagnosis, particularly since the development of a variety of enrichment techniques. Cycloserine cefoxitin fructose agar is still adequate, although reduced concentrations of antimicrobial agents are necessary, and improvements, such as the addition of sodium taurocholate, increase the recovery of spores. Enrichment cultures have markedly increased isolation rates for Clostridium difficile but the significance of these isolates needs to be carefully evaluated. Until simpler and more reliable tests are available in clinical laboratories for the detection of toxins, the isolation of Clostridium difficile from patients with diarrhoeal disease should be considered paramount.

Selective procedures for detecting femtomole quantities of tuberculostearic acid in serum and cerebrospinal fluid by frequency-pulsed electron capture gas-liquid chromatography

Conditions are described for the detection of tuberculostearic acid (10-methyloctadecanoate; C18 X CH3) in cerebrospinal fluid and serum of patients with tuberculous meningitis. C18 X CH3 was found in both the cerebrospinal fluid and serum of patients with tuberculous meningitis at concentrations of 25 to 50 fmol (10(-15) mol). The necessary specificity and sensitivity for detection of C18 X CH3 were obtained by extraction under acid conditions with organic solvent, specific functional group esterification with trichloroethanol, cleanup with disposable reverse-phase sorption chromatography columns, analysis on high-resolution polar and nonpolar capillary columns, and detection by a frequency-pulsed electron capture detector. Use of an IBM 9000 computer equipped with CAP software significantly aided comparison between known C18 X CH3 standards and C18 X CH3 in clinical specimens. Scale expansion and attenuation changes were the major contributions obtained by use of the computer. The data indicate that detection of C18 X CH3 by frequency-pulsed electron capture gas-liquid chromatography may be a valuable aid for early detection of tuberculous meningitis.

Studies of metabolites in diarrheal stool specimens containing Shigella species by frequency-pulsed electron capture gas-liquid chromatography

Eleven diarrheal stool specimens and 10 control stool specimens from Cairo, Egypt, were studied by frequency-pulsed electron capture gas-liquid chromatography (FPEC-GLC). Four cases involving Shigella sonnei, three cases involving Shigella boydii, and four cases involving Shigella flexneri were studied. The aqueous stools were centrifuged, extracted with organic solvents, and derivatized to form specific electron-capturing derivatives of carboxylic acids, alcohols, hydroxy acids, and amines. Analyses were performed on high-resolution glass columns with an instrument equipped with an extremely sensitive electron capture detector that is specific for the detection of electron-capturing compounds. The diarrheal stools studied had specific FPEC-GLC profiles and contained metabolic markers that readily distinguished between the Shigella spp. studied and Escherichia coli producing heat-stable or heat-labile enterotoxins. S. sonnei stools contained hexanoic acid, 2-hydroxy-4-methylmethiobutyric acid, and some unidentified alcohols that distinguished this organism from other enteric pathogens. S. boydii produced an acid that was unique for this species, and S. flexneri produced alcohols that could be used to distinguish between it and other enteric organisms. The FPEC-GLC profiles obtained during this study were also very different from those reported earlier for Clostridium difficile and rotavirus. This study presents further evidence that the selectivity and sensitivity of FPEC-GLC techniques can be used to rapidly identify causative agents of diarrhea and detect physiological changes that occur in the gut during the course of diarrheal illness.

Rapid differentiation of enterotoxigenic Escherichia coli that produce heat-stable and heat-labile toxins by frequency-pulsed electron capture gas-liquid chromatography analysis of diarrheal stool specimens

Thirty-three stool specimens from infants in the village of Tamooh near Cairo, Egypt, were studied by frequency-pulsed electron capture gas-liquid chromatography (FPEC-GLC). In 13 of the diarrheal cases, the suspected causative agent isolated was Escherichia coli which produced heat-stable toxin (ST), and in 10 other cases E. coli that produced heat-labile toxin (LT) were isolated. Ten control stool samples, collected from infants from whom no pathogenic organisms were isolated, were analyzed at the same time. Comparisons also were made against healthy control stools from individuals in the United States who had been previously analyzed by FPEC-GLC (Brooks et al., J. Clin. Microbiol. 20:549-560, 1984). The stools were suspended in water and centrifuged, and the supernatant was extracted with organic solvents and derivatized to form electron-capturing derivatives of carboxylic acids, hydroxy acids, alcohols, and amines. Results from the study showed distinct differences among the FPEC-GLC profiles of E. coli ST-positive stools, of E. coli LT-positive stools, and of the control stool samples. An unidentified compound appearing in the ether-soluble hydroxy acid fraction from E. coli ST-positive stools was tentatively identified by mass spectrometry as 6-methoxy-2-hydroxyhexanoic acid. 6-Methoxy-2-hydroxyhexanoic acid was found in all stools that contained E. coli ST but was not present either in stools from which E. coli LT was isolated or in control samples. 6-Methoxy-2-hydroxyhexanoic acid may prove to be an important marker for use in the identification of E. coli ST. In addition to 6-methoxy-2-hydroxyhexanoic acid, the carboxylic acid, alcohol, and amine FPEC-GLC profiles obtained from stools were very different between these two organisms. The data indicate that FPEC-GLC analysis of diarrheal stool specimens might be a rapid way to distinguish diarrhea caused by E. coli ST, E. coli LT, Clostridium difficile, and rotavirus.

Frequency-pulsed electron capture gas-liquid chromatographic analysis of metabolites produced by Clostridium difficile in broth enriched with amino acids

Clostridium difficile strain CDC A-567 was cultured in Trypticase (BBL Microbiology Systems)-yeast-salt broth supplemented with 0.2% L-leucine, L-norleucine, L-isoleucine, L-tyrosine, or L-tryptophan. Four extractions were done on the spent medium, three at pH 2 and one at pH 10, using CHCL3 or ether. Derivatizations were done with trichloroethanol, heptafluorobutyric anhydride, and heptafluorobutyric anhydride-ethanol. All samples were analyzed with frequency-pulsed electron capture gas-liquid chromatography. A dedicated computer was used to assist in data analysis. C. difficile produced both short-chain and aromatic acids in Trypticase-yeast-salt broth; hydroxy acids were also detected. p-Cresol, indoleacetic acid, 4-methylthio-2-hydroxybutyric acid, and some unidentified alcohols were observed. The basic chloroform extraction contained cadaverine and putrescine. Leucine, norleucine, and isoleucine influenced the production of C5 and C6 acids and alcohols. L-Tyrosine underwent successive degradation to produce p-cresol and aromatic acids as final products. Tryptophan increased the production of indoleacetic, indolepropionic, and indolebutyric acids. Isocaproic acid was produced in relatively high concentrations regardless of medium substitution. The consistent production of iC6 under various substrate conditions indicates that the production of this compound might be consistent enough in vitro to form the basis of a rapid test for detection of C. difficile in stool specimens by frequency-pulsed electron capture gas-liquid chromatography.