Preliminary structure determination of the capsular polysaccharide of Vibrio cholerae O139 Bengal Al1837

Vibrio cholerae O139 Bengal has recently been identified as a cause of epidemic cholera in Asia. In contrast to V. cholerae O1, V. cholerae O139 Bengal has a polysaccharide capsule. As determined by high-performance anion-exchange chromatography and 1H nuclear magnetic resonance analysis, the capsular polysaccharide of V. cholerae O139 Bengal strain Al1837 has six residues in the repeating subunit; this includes one residue each of N-acetylglucosamine, N-acetylquinovosamine (QuiNAc), galacturonic acid (GalA), and galactose and two residues of 3,6-dideoxyxylohexose (Xylhex). The proposed structure is [formula: see text]

Isolation and structural analysis of oligosaccharide phosphates containing the complete carbohydrate chain of the lipopolysaccharide from Vibrio cholerae strain H11 (non-O1)

For the first time, an oligosaccharide has been prepared comprising the lipid A backbone, the core oligosaccharide and one repeating unit of the O-specific polysaccharide (O-chain) of a lipopolysaccharide. Lipopolysaccharide from Vibrio cholerae strain H11 (non-O1) was deacylated and the products were separated by high-performance anion-exchange chromatography. Major fractions were a hexadecasaccharide trisphosphate 1, representing the core-lipid A oligosaccharide substituted by one modified repeating unit of the O-antigenic polysaccharide, a dodecasaccharide trisphosphate 2 and an undecasaccharide trisphosphate 3, representing the core-lipid A region. Oligosaccharide 1 originated from beta-elimination upon alkaline hydrolysis of alpha-galacturonic acid of the O-chain; oligosaccharides 2 and 3 were most likely obtained from naturally occurring lipopolysaccharide species carrying no O-chain. The structures of these compounds were elucidated on the basis of monosaccharide composition, and NMR investigations comprising correlation spectroscopy, total correlation spectroscopy and nuclear Overhauser enhancement spectroscopy experiments, as well as heteronuclear 13C, 1H correlation spectroscopy. The structures are as follows: [formula: see text] where R is beta-L-threo-hex-4-enuronopyranosyl-(1-4)-alpha-Neu-(2-3)-beta-Gal A-(1-3)- beta-QuiN-(1-4)-beta-Sedf-(2- in 1, beta-Sedf-(2- in 2, and H in 3. Where not stated otherwise, sugars are pyranoses of the D-series. Hep is L-glycero-D-manno-heptose, QuiN is 2-amino-2,6-dideoxy-glucose, Kdo is 3-deoxy-D-manno-2-octulosonic acid, Sed is D-altro-heptulose and GalA is galacturonic acid.

A 53 kDa protein of Vibrio cholerae classical strain 0395 involved in intestinal colonization

Mutants of Vibrio cholerae 01 strain 0395 (classical) mutated in genes encoding secretory or cell surface proteins were induced by TnphoA mutagenesis and were selected as blue colonies on L-agar plates containing 5-bromo-4-chloro-3-indolyl phosphate. Southern analysis of the total DNA from blue colonies showed that all mutants had TnphoA insertion in genomic DNA. These mutants were analysed for adherence, colonization and protein profile. Adherence to freshly isolated rabbit intestinal discs was affected in some mutants. The less adhesive mutants were examined for colonization of the intestine of infant mice. One mutant, designated T-87, was extremely poor at colonization and less diarrhaegenic than the parent strain. Analysis of T-87 by SDS-PAGE revealed that two proteins of 53 and 38 kDa were lacking. The 38 kDa protein was identified as OmpU. The 53 kDa protein was extracellular and cells treated with anti-53-kDa antibodies could not colonize the gut of infant mice. The expression of the 53 and 38 kDa proteins in T-87 was dependent of the growth medium. The data suggest that T-87 is mutated in a regulatory gene which regulates the expression of proteins involved in intestinal colonization.

Improved synthesis and the crystal structure of methyl 4,6-dideoxy-4-(3-deoxy-L-glycero-tetronamido)-alpha-D-mannopyrano side, the methyl alpha-glycoside of the intracatenary repeating unit of the O-polysaccharide of Vibrio cholerae O:1

The crude product of deamination of the commercially available L-homoserine was acetylated and the 2-O-acetyl-3-deoxy-L-glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-alpha-D-mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-alpha-D-+ ++mannopyranoside (1, 70-75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy-D-glycero-tetronolactone (prepared from D-homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in approximately 90% yield by deacetylating (Zemplén) the crude mixture of N-acylation products, followed by chromatography.

A gene for the enterotoxin zonula occludens toxin is present in Vibrio mimicus and Vibrio cholerae O139

The presence of the zonula occludens toxin (ZOT) gene, which encodes an enterotoxin produced by serotype O1 strains of the pathogenic bacterium, Vibrio cholerae, in addition to cholera toxin, was investigated in selected strains of V. mimicus and the new pandemic V. cholerae non-O1 serotype O139. The zot gene was detected by polymerase chain reaction (PCR) amplification, using sets of primers based on the sequence of the V. cholerae O1 zot sequence. PCR amplification of genomic DNAs of both cholera toxin gene (ctx) positive and ctx- strains of V. mimicus detected the presence of zot gene. An AccI-EcoRV V. cholerae zot gene fragment designed to overlap PCR products was used as a probe. Southern hybridization studies confirmed that the PCR fragments from V. mimicus and V. cholerae O139 were strongly homologous to the V. cholerae O1 zot gene. The zot gene was found with 3 of 5 strains of V. mimicus of which only one strain harbored the ctx gene. The presence of a zot gene in ctx- toxigenic V. mimicus indicates a possible role of ZOT in the toxigenicity of this species. We conclude that, in addition to ctx, V. mimicus and V. cholerae O139 have the potential to produce ZOT.

Biological activities of lipopolysaccharide isolated from Vibrio cholerae O139, a new epidemic strain for recent cholera in Indian subcontinent

Biological activities of lipopolysaccharide (LPS) isolated from Vibrio cholerae O139, a new causative agent for recent cholera epidemic in Indian subcontinent, were investigated in comparison with those of LPS from O1 V. cholerae. V. cholerae O139 LPS exerted mitogenic activity, lethal toxicity and Shwartzman reaction to the same extent as those observed for O1 V. cholerae LPS, although these activities except for lethal toxicity were obviously lower than those of Salmonella typhimurium LT-2 LPS used as a reference. It was, therefore, suggested that O139 LPS does not contribute to the high infective and pathogenic potentials of the V. cholerae O139 strain as in the case of O1 V. cholerae.

The toxin-co-regulated pilus of Vibrio cholerae O1: a model for type 4 pilus biogenesis?

The toxin-co-regulated pilus (TCP), an important colonization factor of Vibrio cholerae, is similar to the type 4 pilus produced by a variety of pathogenic Gram-negative bacteria. The putative translocation and assembly machinery of TCP has broad similarities with known pilin and nonpilin export mechanisms.

Identification of a novel sugar, 4-amino-4,6-dideoxy-2-O-methylmannose in the lipopolysaccharide of Vibrio cholerae O1 serotype Ogawa

A novel sugar in the lipopolysaccharide of Vibrio cholerae O1 serotype Ogawa has been identified. The sugar was liberated from the lipopolysaccharide when hydrolyzed in 10 M HCl at 90 degrees C for 15 min. The sugar was purified and identified as 4-amino-4,6-dideoxy-2-O-methylmannose (2-O-methylperosamine). Since it was found only in the lipopolysaccharide of Vibrio cholerae O1 serotype Ogawa, it seems that the sugar is one of the specific constituents determining Ogawa serotype specificity.

Purification and characterization of vibrio cholerae O139 fimbriae

A Vibrio cholerae O139 (strain Al-1841) isolated from a patient with a cholera-like disease in Bangladesh predominantly produced new curved, wavy fimbriae (Al-1841 fimbriae) and small numbers of previously reported V. cholerae non-O1 S7-like pili. The former was purified and characterized. The molecular mass of the Al-1841 fimbrial subunit was less than 2.5 kDa, and it was immunologically different from that of V. cholerae non-O1 S7 pili. This novel fimbrial antigen was detected in all 182 Gram-negative strains from five genera tested but was absent from the Gram-positive bacteria tested. The purified Al-1841 fimbriae did not agglutinate human or rabbit erythrocytes.

Immunochemical properties of Vibrio cholerae LPS

Immunochemical analysis of LPS isolated from Vibrio cholerae O1 and non O1 showed that this macromolecular complex shares common antigenic epitopes in the sugar moiety. The epitopes can be detected after mild alkaline hydrolysis of LPS in vitro. Membrane-associating activity of both O1 and non O1 LPS did not indicate any differences of the species.

The structure of the carbohydrate backbone of the core-lipid-A region of the lipopolysaccharide from Vibrio cholerae strain H11 (non-O1)

Lipopolysaccharide from Vibrio cholerae strain H11 (non-O1) was de-O-acylated, dephosphorylated, reduced, de-N-acylated, N-acetylated, and the products were separated by high-performance anion-exchange chromatography (HPAE). A decasaccharide, 1, was isolated as the major product, representing the core oligosaccharide attached to the reduced GlcN-disaccharide lipid A backbone. Its structure was established by compositional and methylation analyses, and extensive NMR investigations including 1H,1H correlation spectroscopy (COSY), total correlation spectroscopy (TOCSY), and nuclear Overhauser enhancement spectroscopy (NOESY), as well as heteronuclear 13C,1H COSY. In another reaction sequence the lipopolysaccharide was hydrolysed with dilute acetic acid and reduced with NaBH4. The resulting core fractions were separated by HPAE giving seven individual octasaccharides differing at the reducing 3-deoxy-D-manno-octulosonic acid (Kdo) residue. A major product, 2, was isolated and investigated by the same methods as described for the decasaccharide 1. The following structures are proposed for compounds 1 and 2: alpha-D-GlcNAcp-(1-7)-[beta-D-Galp-(1-3)-]-alpha-Hepp-(1-2)- alpha-Hepp- (1-3)-[beta-D-Glcp-(1-4)-]- [alpha-D-Glcp-(1-6)-]-alpha-Hepp-(1-5)-R, where R is alpha-Kdop-(2-6)-beta-D-GlcNAcp-(1-6)-D-GlcNAcol in 1 and 4,8-anhydro-Kdool in 2, and Hep is L-glycero-D-manno-heptose. In lipopolysaccharide, the terminal residue of alpha-D-glucosamine possessed a free amino group, as proved by deamination with nitrous acid and the 1H-NMR spectrum of de-O-acylated lipopolysaccharide. The conformational preferences of the terminal core heptasaccharide was assessed by Monte Carlo simulations combined with restrained calculations of side chains based on experimentally determined proton-coupling constants. These calculations, confirmed by NOE data, displayed several long-range interactions, which resulted in a well-defined three-dimensional structure of the core oligosaccharide.

Purification and characterization of pili of a Vibrio cholerae non-O1 strain

Pili of the Vibrio cholerae non-O1 strain V10 were purified and characterized. The V10 pili were physicochemically and immunologically different from those of the previously reported V. cholerae non-O1 strain S7, although the pili of the two strains had homologous N-terminal amino acid sequences. V10 plus antigen was detected only in V. cholerae non-O1 strains.

Characterization of Vibrio cholerae O139 synonym Bengal isolated from patients with cholera-like disease in Bangladesh

Vibrio cholerae O139 (synonym Bengal), a novel serovar of V. cholerae, is the causative agent of large outbreaks of cholera-like illness currently sweeping India and Bangladesh. Eight randomly selected V. cholerae O139 isolates were studied for their biological properties, which were compared with those of V. cholerae O1 and other V. cholerae non-O1. The V. cholerae O139 isolates were characterized by the production of large amount of cholera toxin, hemagglutination, weak hemolytic properties, resistance to polymyxin B, lysogeny with, and production of, kappa type phage (4/8 isolates only), and resistance to both classical and El Tor-specific phages. Thus, V. cholerae O139 isolates had an overall similarity with V. cholerae O1 El Tor.

O-antigenic lipopolysaccharide of Vibrio cholerae O139 Bengal, a new epidemic strain for recent cholera in the Indian subcontinent

Lipopolysaccharide (LPS) from Vibrio cholerae O139 Bengal contained colitose (3,6-dideoxy-L-galactose) in addition to glucose, L-glycero-D-manno-heptose, fructose, glucosamine and quinovosamine in its polysaccharide and only glucosamine in lipid A, while perosamine, a characteristic component sugar of V. cholerae O1 LPS, was absent. 3-Hydroxydodecanoic, tetradecanoic and hexadecanoic acids as ester-bound fatty acids and 3-hydroxytetradecanoic acid as amide-bound fatty acid were identified in the lipid A. A very high serological specificity of O139 LPS distinct from that of O1 V. cholerae was demonstrated by passive hemolysis and passive hemolysis inhibition tests by using the LPS either as antigen for sensitizing sheep red blood cells or as inhibitor in the latter test.

Entero-cytolysin (EC) from Vibrio cholerae non-O1 (some properties and pore-forming activity)

A thermolabile extracellular entero-cytolysin (EC) from Vibrio cholerae non-O1 was purified by ammonium sulphate fractionation, DE-52 cellulose ion exchange chromatography, gel-filtration on Ultrogel AcA-44 and high performance liquid chromatography on a Mono Q. The purified EC had a molecular weight of 63 kD and an isoelectric point of 6.2. It was not inactivated by cholesterol or 5,5'-dithio-bis(2-nitrobenzoic acid), nor activated by dithiothreitol. EC had no immunological cross-reactivity with cholera toxin. The EC caused fluid accumulation in the intestines of infant rabbits, death of mice by intravenous injection, and increased vascular permeability in the paw oedema test in mice. V. cholerae non-O1 EC lysed erythrocytes from various species and cultured cells (CHO, L-929, L-41, HEp-2, Vero, MDCK and BHK-21). In contrast to cholera toxin, EC caused crude destruction of target cells. The EC caused hemolysis by a colloid-osmotic mechanism due to the formation of hydrophilic pores of 1.8-2.0 nm diameter in the cell membrane. This EC also was able to open pores in lipid membranes. The induced channels were anion-selective and had a diameter of 1.8-2.0 nm.

Differential scanning calorimetry investigations on LPS and free lipids A of the bacterial cell wall

Differential scanning calorimetry (DSC) was used to investigate the thermal stability and behaviour of the lipopolysaccharides (LPS) of the outer membrane of Gram-negative bacteria and their lipid portion. DSC curves of LPS show thermal features between 200 and 129 degrees C (depolymerization) and between -13 and -36 degrees C (cooling phase transition). Both effects were related to the relative strength of the linkage types in the O-chain structure and to their capacity for intermolecular hydrogen bonding. DSC curves of lipids A show endotherm peaks between 40 and 24 degrees C, around 15 degrees C and between -23 and -4 degrees C. Based on these effects, strong differences in thermal behaviour can be observed between that of Brucella and Vibrio cholerae on the one hand, and that of Escherichia coli and Shigella flexneri on the other. Fluidity of the acyl chains and lyotropism, which are important parameters in expression of biological activities, are discussed using the above data. To explain some properties, fluidity could be related to the temperature of the gel<==>liquid crystalline (beta<==>alpha) phase transition, which occurs at physiological temperature. Nevertheless, fluidity could be related to temperature of the previous thermal effect (between 6 and 20 degrees C), for which a softening or partial melting of the sample has been evidenced. The thermal effect measured between -23 degrees C and -4 degrees C indicates a greatly reduced water concentration of lipid A from Brucella, thus explaining its early fusion process and its activity by means of hydrophobic interactions.

Structural studies of the Vibrio cholerae O:5 O-antigen polysaccharide

The O-polysaccharide from Vibrio cholerae O:5 has been investigated, using NMR spectroscopy as the main method. Fast atom bombardment mass spectrometry (FABMS) studies of fragments obtained on treatment with anhydrous hydrogen fluoride or methanolic hydrogen chloride gave further structural information. Some structural features were also determined by comparison of nuclear Overhauser enhancement (NOE) contacts with calculated H-H distance in different oligosaccharide models. It is concluded that the O-polysaccharide has the following structure, in which D-Qui p NAc4NAc is 2,4-diacetamido-2,4,6-trideoxy-D-glucose, and D-Fuc p 3NX is 3-amino-3,6-dideoxy-D-galactose acylated with a (R,R)-3-hydroxy-3-methyl-5-oxoproline group. [formula: see text]

Cell-associated hemagglutinin of classical vibrio cholerae O1 with reference to intestinal adhesion

Vibrio cholerae O1 86B3 biovar cholerae has at least two types of cell-associated hemagglutinin. One is cell wall-associated and L-fucose sensitive, whereas the other is pili-associated and D-mannose sensitive. A pilus rich variant of 86B3 and a poorly piliated parent strain adhered equally to the rabbit intestine. This adhesion was inhibited by L-fucose but not by D-mannose. A Fab fraction prepared from anti-pilus antibody did not inhibit the adhesion. These results suggest that not the pili but a colonization factor located in the outer membrane of the organisms plays a role in intestinal adhesion.

A 20-kDa pilus protein with haemagglutination and intestinal adherence properties expressed by a clinical isolate of non-01 Vibrio cholerae

A clinical isolate of non-01 V. cholerae (10325) was shown to exhibit higher haemagglutination and intestinal adherence activities in vitro when grown in enriched media, such as trypticase soy broth (TSB) as compared to those of cells grown in a synthetic Tris-buffered or 'T'-medium. A comparison of their cell-surface protein and lipopolysaccharide profiles suggested the involvement of a 20-kDa protein in the cellular adherence process. An antiserum, raised specifically against the 20-kDa protein, recognised pilus structures on the surface of TSB grown cells. Further studies showed that the pilus was morphologically as well as antigenically distinct from toxin coregulated pilus (TCP) or other types of pili expressed by both 01 and non-01 organisms. Inhibition data established the involvement of the 20-kDa protein in haemagglutination as well as intestinal tissue adherence activities of the parent organism.

N-3-hydroxypropionyl-alpha-D-perosamine homopolymer constituting the O-chain of lipopolysaccharides from Vibrio bioserogroup 1875 possessing antigenic factor(s) in common with O1 Vibrio cholerae

A structural study was performed by 13C-n.m.r. spectroscopy and methylation analysis of the O-chain of lipopolysaccharide (LPS) from Vibrio bioserogroup 1875 possessing antigenic factor(s) in common with O1 Vibrio cholerae. It was demonstrated to contain a linear homopolymer of (1-->2)-linked N-3-hydroxypropionyl-alpha-D-perosamine [4-(3-hydroxypropanamido)-4,6-dideoxy-alpha-D-mannopyranose], which is very similar to, but not identical with, both (1-->2)-linked linear N-3-deoxy-L-glycero-tetronyl(S-2,4-dihydroxybutyryl)-alpha-D - perosamine homopolymer and (1-->2)-linked linear N-acetyl-alpha-D-perosamine homopolymer which constitute the O-chains of O1 V. cholerae and non-O1 V. cholerae bioserogroup Hakata LPS respectively.

Comparison of Vibrio cholerae serotype 01 strains isolated from patients and the aquatic environment

Vibrio cholerae 01 strains of El Tor and Classical biotypes and Ogawa and Inaba serotypes were isolated from both patients and pond water, the latter used by the patients from whom the V. cholerae 01 strains had been isolated. Paired strains, i.e. from the patient and from the pond used by the patient, were compared. All strains were found to be non-hydrophobic and agglutinating in ammonium sulphate (2.0-2.5 M). They demonstrated similar antibiogram patterns and plasmids were not detected. Except for one clinical and one environmental strain, all strains caused fluid accumulation in the rabbit ileal loop (RIL). The outer membrane protein profiles of both clinical and environmental strains were nearly identical, except for the presence of an additional 22 kDa polypeptide, observed only in environmental strains. The protein profiles of two environmental isolates, analysed after passage through rabbits by oral feeding, were altered, demonstrating a significant decrease in the number of protein bands after animal passage but with the major protein band pattern remaining unchanged. Each passaged strain, however, demonstrated properties similar to the non-passaged culture in cell surface hydrophobicity, plasmid profile, antibiogram patterns, and enterotoxin production.

Rapid polymerase chain reaction method for detection of Vibrio cholerae in foods

The polymerase chain reaction was used to selectively amplify sequences within the cholera toxin operon from Vibrio cholerae O1. Oysters, crabmeat, shrimp, and lettuce were seeded with V. cholerae and then homogenized or washed with alkaline peptone water, followed by short-term (6- to 8-h) enrichment. A detection limit of as few as 1 V. cholerae CFU per 10 g of food was obtained with amplification reactions from crude bacterial lysates. The method is extremely rapid and obviates the need for DNA isolation from a variety of complex food matrices.