Biomedical subjects

A Weintraub

Publications and source records attributed to A Weintraub.

At least 37 records · Page 2Linked to original sources

PubMed1999

Structure determination of the O-antigenic polysaccharide from the enteroinvasive Escherichia coli O136.

The structure of the O-antigen polysaccharide of the lipopolysaccharide from the enteroinvasive Escherichia coli O136 has been elucidated. The composition of the repeating unit was established by sugar and methylation analysis together with 1H and 13C NMR spectroscopy. Two-dimensional nuclear Overhauser effect spectroscopy (NOESY) and heteronuclear multiple-bond correlation experiments were used to deduce the sequence. The absolute configuration for the nonulosonic acid (NonA) could be determined using spin-spin coupling constants, 13C chemical shifts and NOESY. The anomeric configuration of the NonA was determined via vicinal and geminal 13C,1H coupling constants. The structure of the repeating unit of the polysaccharide from E. coli O136 is as follows, in which beta-NonpA is 5,7-diacetamido-3,5,7, 9-tetradeoxy-Lglycero-beta-Lmanno-nonulosonic acid: -->4)-beta-NonpA-(2-->4)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->

Carbohydrate Conformation↗

PubMed1999

Structural elucidation of the O-antigenic polysaccharides from Escherichia coli O21 and the enteroaggregative Escherichia coli strain 105.

The structure of the O-antigen polysaccharide of the lipopolysaccharide from an enteroaggregative Escherichia coli (strain 105) has been elucidated, using primarily one-dimensional and two-dimensional NMR experiments. The sequence of residues was deduced with heteronuclear multiple-bond correlation and NOESY experiments. The structure of the repeating unit of the polysaccharide from the enteroaggregative E. coli is as follows:[sequence: see text] The structure of the O-antigen from enteroaggregative E. coli strain 105 was shown to be identical with that of E. coli O21 by sugar and methylation analyses as well as by 1H-NMR and 13C-NMR spectroscopy.

Bacterial Adhesion↗

PubMed1999

Structural studies utilizing 13C-enrichment of the O-antigen polysaccharide from the enterotoxigenic Escherichia coli O159 cross-reacting with Shigella dysenteriae type 4.

The structure of the O-antigen polysaccharide from Escherichia coli O159 has been determined using primarily NMR spectroscopy of the 13C-enriched polysaccharide. The sequence of the sugar residues could be determined by heteronuclear multiple bond connectivity NMR experiments. The polysaccharide is composed of a pentasaccharide repeating unit with the following structure: [sequence: see text] Matrix assisted laser desorption ionization mass spectrometry was performed on intact lipopolysaccharide and from the resulting molecular mass the O-antigen part was estimated to contain approximately 23 repeating units. Cross-reactivity of this O-antigen to that of Shigella dysenteriae type 4 was confirmed using enzyme-linked immunoabsorbant assay.

Adult↗

PubMed1999

Structural studies of the O-antigen polysaccharide from the enteroinvasive Escherichia coli O164 cross-reacting with Shigella dysenteriae type 3.

The structure of the O-antigen polysaccharide from Escherichia coli O164 has been determined. Nuclear magnetic resonance spectroscopy together with component and methylation analyses of lipid free polysaccharide were the principal methods used. The sequence of the sugar residues could be determined by NOESY and heteronuclear multiple bond connectivity NMR experiments. It is concluded that the polysaccharide is composed of a pentasaccharide repeating unit with the following structure: [structure: see text]. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was performed on intact lipopolysaccharide and from the resulting molecular mass, the O-antigen part was estimated to contain approximately 24 repeating units. The nature of the previously reported cross-reactivity of this O-antigen to those of Escherichia coli O124 and Shigella dysenteriae type 3 is discussed.

Animals↗

PubMed1999

Prevalence of enterotoxigenic Bacteroides fragilis in adult patients with diarrhea and healthy controls.

Enterotoxigenic strains of Bacteroides fragilis (ETBF) have been associated with diarrheal diseases in animals and humans. The enterotoxin of ETBF induces fluid changes in ligated intestinal segments and a cytotoxic response in HT29/C1 cells. An assay based on immunomagnetic-beads separation in combination with PCR was used to detect ETBF in fecal samples from patients with diarrhea and healthy Swedish adults. A total of 922 fecal samples were analyzed in this study, including 728 samples from patients with diarrhea and 194 samples from controls. ETBF was detected in 195 of 728 patients (26.8%) and 24 of 194 healthy controls (12.4%). The difference between the two groups was statistically significant (P<.01). ETBF was the only potential diarrheal agent in 91 (12.5%) of 728 patients. All ETBF-positive samples from patients and controls were also positive in the HT29/C1 assay. The data show high carriage of ETBF in Swedish adults, which might be associated with diarrheal disease.

Adolescent↗

PubMed1999

Phagocytosis of Vibrio cholerae O139 Bengal by human polymorphonuclear leukocytes.

Capsulated bacteria exhibit serum (complement) resistance and resistance to phagocytosis, which result in disseminated infections. Vibrio cholerae O139 strains possess a thin capsule and have been found to be partially serum resistant in a previous study. In the present study, compared to a standard capsulated Klebsiella pneumoniae strain, which showed total resistance to killing by phagocytosis, V. cholerae O139 strains were shown to be only partially resistant, with most strains showing <40% survival. These findings may explain the relative rarity of V. cholerae O139 bacteremia in cholera caused by this organism.

Bacterial Capsules↗

PubMed1999

The outer membrane of Brucella ovis shows increased permeability to hydrophobic probes and is more susceptible to cationic peptides than are the outer membranes of mutant rough Brucella abortus strains.

The permeability of the outer membrane (OM) to hydrophobic probes and its susceptibility to bactericidal cationic peptides were investigated for natural rough Brucella ovis and for mutant rough Brucella abortus strains. The OM of B. ovis displayed an abrupt and faster kinetic profile than rough B. abortus during the uptake of the hydrophobic probe N-phenyl-naphthylamine. B. ovis was more sensitive than rough B. abortus to the action of cationic peptides. Bactenecins 5 and 7 induced morphological alterations on the OMs of both rough Brucella strains. B. ovis lipopolysaccharide (LPS) captured considerably more polymyxin B than LPSs from both rough and smooth B. abortus strains. Polymyxin B, poly-L-lysine, and poly-L-ornithine produced a thick coating on the surfaces of both strains, which was more evident in B. ovis than in rough B. abortus. The distinct functional properties of the OMs of these two rough strains correlate with some structural differences of their OMs and with their different biological behaviors in animals and culture cells.

Animals↗

PubMed1999

Antimicrobial susceptibility of anaerobic and aerobic bacteria isolated from patients with mixed infections in Nicaragua.

The agar dilution method was used to test the activity of ampicillin, benzylpenicillin, cefoxitin, imipenem, clindamycin, metronidazole, chloramphenicol, gentamicin, methicillin and vancomycin against 241 anaerobic and 227 aerobic bacteria isolated from 136 patients with intraabdominal infections and 49 with nonintraabdominal infections. Beta-lactamase production was tested in all strains. Overall, imipenem, metronidazole and chloramphenicol were the most active antimicrobial agents against anaerobic bacteria followed by clindamycin. Only the Bacteroides fragilis group was shown to be less susceptible to clindamycin (MIC90 8 mg/l). Ampicillin and cefoxitin were the least active beta-lactam antibiotics against the most common isolated B. fragilis group strains (MIC(90) >1024 and 64 mg/l, respectively) and against Escherichia coli strains (MIC(90) >1024 and >1024 mg/l, respectively). Chloramphenicol showed low activity against the Gram-negative aerobic bacteria, while gentamicin had good activity against the aerobic bacteria tested, except for E. coli and Pseudomonas. Among the Gram-positive aerobic and anaerobic bacteria tested, Staphylococcus aureus was shown to be less susceptible to beta-lactam antibiotics (29% were methicillin resistant). No vancomycin-resistant S. aureus strains were found. A good correlation between beta-lactamase production and beta-lactam resistance was observed.

Bacteria, Aerobic↗

PubMed1999

Antimicrobial susceptibility of anaerobicand aerobic bacteria isolated from patientswith mixed infections in Nicaragua.

Journal Article↗

PubMed1998

Structural determination of the O-antigenic polysaccharide from Escherichia coli O35 and cross-reactivity to Salmonella arizonae O62.

The structure of the O-antigenic polysaccharide from Escherichia coli O35 has been investigated with the aid of NMR spectroscopy, sugar and methylation analyses. The sequence of the sugar residues could be determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments. The polysaccharide is composed of hexasaccharide repeating units with the following structure, where Rha and GalNAcAN represent rhamnose and 2-acetamido-2-deoxy-galacturonamide, respectively: carbohydrate sequence [see text]. The O-antigen of Escherichia coli O35 is similar to the O-specific polysaccharide from Salmonella arizonae O62, which instead has a terminal 2-acetamido-2-deoxy-alpha-D-galacturonic acid residue. Immunochemical analyses using a rabbit antiserum specific for the Salmonella arizonae O62 O-antigen showed an identical reactivity with both lipopolysaccharides.

Carbohydrate Sequence↗

PubMed1998

Structural studies of the O-antigenic polysaccharide from Escherichia coli O139.

The structure of the O-antigenic polysaccharide from Escherichia coli O139 has been investigated with the aid of NMR spectroscopy, and sugar and methylation analyses. The sequence of the sugar residues was determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments. The polysaccharide is composed of heptasaccharide repeating units containing 0.6 mol O-acetyl groups/repeating unit. The following structure is concluded, where Rha represents rhamnose. [structure in text]

Acetylation↗

PubMed1998

Structure of the O-antigen of Vibrio cholerae O155 that shares a putative D-galactose 4,6-cyclophosphate-associated epitope with V. cholerae O139 Bengal.

The O-specific polysaccharide of Vibrio cholerae 0155 was studied by sugar and methylation analyses, dephosphorylation with 48% hydrofluoric acid, 1H- and 13C-NMR spectroscopy, including two-dimensional COSY, TOCSY, NOESY, and heteronuclear single-quantum coherence (HSQC) experiments. The following structure of the pentasaccharide repeating unit of the polysaccharide was established: carbohydrate sequence [see text]. An unusual component, D-galactose 4,6-cyclophosphate, has been reported previously as a component of the capsular polysaccharide and O-antigen of V. cholerae O139 Bengal and appears to be responsible for the known serological cross-reactivity between V. cholerae O139 and O155.

Carbohydrate Conformation↗

PubMed1998

Structural determination of the O-antigenic polysaccharide from Escherichia coli O141.

The structure of the O-antigenic polysaccharide from Escherichia coli O141 has been determined. NMR spectroscopy and sugar and methylation analyses were the principal methods used. The sequence of the sugar residues could be determined by NOESY and heteronuclear multiple-bond connectivity (HMBC-) NMR experiments. The polysaccharide is composed of pentasaccharide repeating units with 1 O-acetyl group/repeating unit. The following structure, where Rha is 6-deoxymannose is concluded: carbohydrate sequence [see text].

Animals↗

PubMed1998

CD14-dependent activation of human endothelial cells by Bacteroides fragilis outer membrane.

We studied the capacity of isolated Bacteriodes fragilis outer membrane, B. fragilis NCTC9343 lipopolysaccharide (LPS; endotoxin), and B. fragilis NCTC9343 capsular polysaccharides to activate human umbilical vein endothelial cell (HUVEC) monolayers. To assess HUVEC activation, E-selectin expression was measured by enzyme-linked immunosorbent assay (ELISA), Northern blot analysis for E-selectin-specific mRNA, and electrophoretic gel mobility shift assay (EMSA) for NF-kappa B, a transcription factor necessary for E-selectin gene activation. Exposure of HUVECs to B. fragilis outer membrane fractions, separated from other components of the B. fragilis cell wall by isopycnic, sucrose gradient centrifugation, significantly increased surface expression of E-selectin and induced functional endothelial cell-dependent leukocyte adhesion. B. fragilis outer membranes induced translocation of NF-kappa B to HUVEC nuclei and accumulation of E-selectin mRNA in HUVEC cytoplasm. E-selectin expression induced by B. fragilis outer membranes was not blocked by polymixin B. In contrast, E-selectin expression induced by outer membrane fractions purified from E. coli was competitively inhibited by polymixin B. Neither purified B. fragilis LPS, a prominent constituent of the outer membrane, nor purified B. fragilis capsular polysaccharides induced HUVEC activation. Two different monoclonal antibodies directed against human CD14 completely inhibited B. fragilis outer membrane-induced NF-kappa B activation, E-selectin transcription, and E-selectin surface expression. We conclude that the outer membrane component of the B. fragilis cell wall contains a proinflammatory factor(s), that is not LPS, which induces human endothelial cell activation by a soluble CD14-dependent mechanism.

Antibodies, Monoclonal↗

PubMed1998

Structural analysis of the O-antigenic polysaccharide from Vibrio mimicus N-1990.

The O-antigenic polysaccharide part of the lipopolysaccharide from Vibrio mimicus N-1990 has been investigated. Sugar and methylation analysis of native and dephosphorylated polysaccharide together with NMR spectroscopy show that the polysaccharide is composed of tetrasaccharide repeating units. The structure of the repeating unit of the polysaccharide from V. mimicus N-1990 could be determined as: -->4)-alpha-D-GalpNAc-(1-->3)-beta-D-GalpNAc-(1-->2)-4,6-P-beta-D-Galp-( 1-->3)-alpha-D-GalpNAc-(1-->. The V. mimicus N-1990 strain cross-reacts with antibodies elicited against the Vibrio cholerae O139. The nature of this cross-reactivity resides in the partial structure comprising the galactosyl residue substituted with a cyclic phosphate. This element is present in the cell-wall-associated polysaccharides of both strains.

Carbohydrate Conformation↗

PubMed1998

Structural determination of the O-antigenic polysaccharide from the enterotoxigenic Escherichia coli O147.

The structure of the O-antigenic polysaccharide from enterotoxigenic Escherichia coli O147 has been determined by NMR spectroscopy, and component and methylation analyses. The sequence of the sugar residues could be determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments. It is concluded that the polysaccharide is composed of tetrasaccharide repeating units with the following structure: -->4)-beta-D-GalpA-(1-->3)-beta-D-GalpNAc-(1-->2)-alpha-L-Rhap+ ++-(1-->2)-alpha-L-Rhap-(1-->, where Rha represents 6-deoxymannose. The O-antigen of E. coli O147 is identical to the repeating unit of Shigella flexneri serotype 6 lipopolysaccharide, except that the latter contains an O-acetyl group at C3 of the rhamnosyl residue substituted by the N-acetylgalactosamine residue. Immunochemical analyses using a monoclonal antibody specific for the S. flexneri serotype 6 O-antigen showed an identical reactivity with both lipopolysaccharides.

Carbohydrate Sequence↗

PubMed1998

Identification of Bacteroides fragilisby a modified immuno polymerase chain reaction (mIPCR), using a specific monoclonal antibody.

Bacteroides fragilis is the anaerobic species most commonly isolated from human clinical specimens, and is resistant to many antimicrobial agents. A monoclonal antibody, mAb4H8 (IgG3), reacting with a specific epitope in the lipopolysaccharide (LPS) isolated from most of the B. fragilis strains, was produced and employed with modified Immuno Polymerase Chain Reaction (mIPCR) for identification of B. fragilis with a detection limit of 10(4) cfu/mL bacterial suspension. A number of bacterial strains were examined, including B. fragilis, Bacteroides spp. other than B. fragilis and other genera. All the B. fragilis strains with the immunodominant (beta1,6-linked D-galactosyl chain) epitope were positive. None of the other strains showed the positive reaction. The results indicate that mIPCR assay with mAb4H8 has a high specificity and high sensitivity.

Journal Article↗

PubMed1998

More on the structure of Vibrio cholerae O22 lipopolysaccharide.

The structure of a short-chain lipopolysaccharide (LPS) of Vibrio cholerae O22 strain 169-68, that cross-reacts with V. cholerae O139 Bengal, was elucidated. The structure differs in detail from that reported on another strain of O22 [A.D. Cox, J-R. Brisson, P. Thibault and M.B. Perry, Carbohydr. Res., 304 (1997) 191-208]. The similarity and difference between the LPS structures of the two strains as well as between O22 and O139 are discussed.

Carbohydrate Conformation↗