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PubMed1995

Structural studies of the putative O-specific polysaccharide of Acinetobacter baumannii O2 containing 3,6-dideoxy-3-N-(D-3-hydroxybutyryl)amino-D-galactose.

A polysaccharide containing D-galactose, 2-deoxy-2-N-acetylamino-D-galactose and 3,6-dideoxy-3-N-(D-3-hydroxybutyryl)amino-D-galactose, probably corresponding to the lipopolysaccharide side chain, was obtained from an aqueous phenol extract of isolated cell walls from Acinetobacter baumannii strain O2. By means of NMR studies and chemical degradations, the repeating unit of the polymer was identified as a branched hexasaccharide of the structure shown, where Fuc3N represents 3-amino-3,6-dideoxygalactose and R represents D-3-hydroxybutyryl. Serological tests indicated that the polymer corresponded to the O2 antigen.

Acinetobacter↗
PubMed1996

Structure of the O-specific polysaccharide of Acinetobacter baumannii O5 containing 2-acetamido-2-deoxy-D-galacturonic acid.

A polysaccharide containing 2-acetamido-2-deoxy-D-glucose (GlcNAc), 2-acetamido-2-deoxy-L-fucose (FucNAc), and 2-acetamido-2-deoxy-D-galacturonic acid (GalNAcA) was isolated from an aqueous phenol extract of lipid-free, isolated cell walls of the reference strain for Acinetobacter baumannii serogroup O5, by mild acid hydrolysis of the extract and chromatography of the water-soluble products on Sephadex G-50. By means of NMR studies, methylation analysis, carboxyl reduction and chemical degradations, the repeating unit of the polymer was identified as a branched tetrasaccharide of the structure shown. The serologically active polymer is believed to correspond to the side chain of the O5 lipopolysaccharide: [table: see text]

Acinetobacter↗
PubMed1996

Structural studies of the putative O-specific polysaccharide of Acinetobacter baumannii O11.

A major polysaccharide containing D-galactose, D-glucose and 2-acetamido-2-deoxy-D-galactose was obtained after mild acid hydrolysis of the water-soluble material released by treatment of cell walls from Acinetobacter baumannii strain O11 with hot, aqueous phenol. By means of NMR studies, Smith degradation and N-deacetylation/deamination, the repeating unit of the polymer was identified as a branched pentasaccharide of the structure shown. Also present was a minor polymer containing glucose, 2-acetamido-2-deoxyglucose-and 2-acetamido-2-deoxygalactose, the structure of which was not elucidated. On serological testing, the polymeric material was shown to correspond to the O-antigenic moiety of the parent extract (assumed to be lipopolysaccharide) and circumstantial evidence indicated that O11 specificity was conferred by the major polymer. [formula: see text]

Acinetobacter↗
PubMed1997

Structural investigation of the lipopolysaccharide from Acinetobacter haemolyticus strain NCTC 10305 (ATCC 17906, DNA group 4).

The structure of the lipopolysaccharide (LPS) from Acinetobacter haemolyticus strain NCTC 10305 (DNA group 4) was elucidated by means of analytical chemistry, NMR spectroscopy and fast-atom-bombardment mass spectrometry. Several oligosaccharides were obtained after deacylation or successive de-O-acylation, dephosphorylation, reduction, and de-N-acylation of LPS. In the major fraction of the LPS, the core is attached to the lipid A through D-glycero-D-talo-2-octulopyranosonic acid (Ko), whereas in a minor fraction (<20%) Ko is replaced by 3-deoxy-D-manno-octulopyranosonic acid (Kdo). The structures of the phosphorylated carbohydrate backbones of these LPS fractions are [structure: see text] with Dha = 3-deoxy-D-lyxo-2-heptulosaric acid, Sug = sugar and is Ko in a major fraction and Kdo in a minor fraction. All sugar residues have the D-configuration and are present in the pyranose form. Mass spectrometry of de-O-acylated LPS revealed the presence of an additional hexose residue in minor amounts, the position and nature of which could not be identified.

Acinetobacter↗
PubMed1997

Structures of polymeric products isolated from the lipopolysaccharides of reference strains for Acinetobacter baumannii O23 and O12.

A polysaccharide containing D-galactose (Gal), 2-acetamido-2-deoxy-D-galactose (GalNAc), 2-acetamido-2-deoxy-D-glucose (GlcNAc), and 3-deoxy-3-(D-3-hydroxybutyramido)-D-quinovose (Qui3NR) was isolated from lipopolysaccharide (LPS) obtained from cells walls of the reference strain for Acinetobacter baumannii O23. By means of NMR studies, methylation analysis, and chemical degradations, the repeating unit of the polymer was identified as a branched pentasaccharide with the structure 1. The same polymer was apparently also present in LPS of the reference strain for serogroup O12, together with a second polymer based on a branched tetrasaccharide with the structure 2. This second polymer has previously been isolated as the O16 antigen of A. baumannii [Haseley, S.R., Diggle, H.J. & Wilkinson, S. G. (1996) Carbohydr. Res. 293, 259-265] and is probably present as a minor component of the LPS of A. baumannii O11 [Haseley, S.R. & Wilkinson, S.G. (1996) Eur. J. Biochem. 237, 266-271]. [Sequence: see text]

Acinetobacter↗
PubMed1997

Structural and serological characterisation of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter haemolyticus strain ATCC 17906.

A polysaccharide containing 2-acetamido-2-deoxy-D-galacturonic acid (GalNAcA), 2.4-diacetamido-2,4,6-trideoxy-D-glucose (QuiNAc4NAc), and D-alanine (Ala) was isolated from the water-soluble lipopolysaccharide (LPS) originating from the reference strain for Acinetobacter haemolyticus (DNA group 4) strain ATCC 17906. The polysaccharide, characterised by means of monosaccharide analyses and NMR studies, was shown to be based on a linear trisaccharide repeating unit, as shown below, with the alanine group amide-bound to position 6 of one GalNAcA residue. It was specifically recognised in western blots by polyclonal rabbit antisera. [structure: see text]

Acinetobacter↗
PubMed1997

Structural studies of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter (DNA group 11) strain 94 containing 3-amino-3,6-dideoxy-D-galactose substituted by the previously unknown amide-linked L-2-acetoxypropionic acid or L-2-hydroxypropionic acid.

A polysaccharide containing D-Gal, D-GalNAc, 3-(L-2-acetoxypropionamido)-3,6-dideoxy-D-galactose (approximately 80%) and 3-(L-2-hydroxypropionamido)-3,6-dideoxy-D-galactose (approximately 20%) was isolated by mild acid hydrolysis, followed by gel-permeation chromatography, from the phenol-soluble lipopolysaccharide (phenol/water extracted) derived from Acinetobacter strain 94. The polysaccharide, characterised by means of monosaccharide analyses, partial acid hydrolysis, and NMR studies, consisted of a branched tetrasaccharide repeating unit, as depicted below, in which Fucp3Nacyl represents 3-(L-2-hydroxypropionamido)-3,6-dideoxy-D-galactose, in which approximately 80% of the acyl residues are O-acetylated. These Fucp3N derivatives and an O-acetylated acyl group are therefore constituents of bacterial LPS, but to our knowledge are not present in any other natural carbohydrates. [sturcture: see text]

Acinetobacter↗
PubMed1997

The structure of the carbohydrate backbone of the lipopolysaccharide from Acinetobacter strain ATCC 17905.

The structure of the carbohydrate backbone of the lipopolysaccharide from Acinetobacter strain ATCC 17905 was studied. After deacylation of the lipopolysaccharide, a mixture of two compounds (ratio approximately 2:1) was isolated by high-performance anion-exchange chromatography, the structures of which were determined by NMR spectroscopy and electrospray-mass spectrometry as [STRUCUTRE IN TEXT] [Sug, 3-deoxy-D-manno-2-octulopyranosonic acid (Kdo) in oligosaccharide 1 (major portion) and D-glycero-D-talo-2-octulopyranosonic acid (Ko) in oligosaccharide 2 (minor portion)]. All monosaccharide residues also possess the D-configuration and are present in the pyranose form.

Acinetobacter↗
PubMed1997

Structural and serological characterisation of the O-specific polysaccharide from lipopolysaccharide of Acinetobacter calcoaceticus strain 7 (DNA group 1).

S-form lipopolysaccharide was isolated by phenol/water extraction from a strain of Acinetobacter calcoaceticus (DNA group 1 ). The structure of the O-antigenic polysaccharide was determined by compositional analysis and NMR spectroscopy of the de-O-acylated lipopolysaccharide. The isolated polysaccharide obtained after hydrolysis of lipopolysaccharide in 0.01 M trifluoroacetic acid has the following structure: [STRUCTURE IN TEXT] in which Pyr is pyruvate. The O-acetyl substitution of D-Gal was non-stoichiometric. The O-antigen was specifically recognised in western blots by polyclonal rabbit antisera.

Acinetobacter calcoaceticus↗
PubMed1997

Structural studies of the putative O-specific polysaccharide of Acinetobacter baumannii O24 containing 5,7-diamino-3,5,7,9-tetradeoxy-L-glycero-D-galacto-nonulosonic acid.

A polysaccharide containing D-GlcN, 2-amino-2,6-dideoxy-L-galactose (L-FucN), and 7-acetamido-5-acylamino-3,5,7,9-tetradeoxy-L-glycero-D-galacto-nonulo sonic acid (LegAX), in which the acyl group (X) is either S-3-hydroxybutyryl (50%) or acetyl (50%), was isolated by mild acid hydrolysis treatment, followed by gel-permeation chromatography, of the water-soluble lipopolysaccharide from Acinetobacter baumannii serogroup O24. The polysaccharide, characterised by means of monosaccharide analyses, partial acid hydrolysis, methylation analysis and NMR studies, was shown to have a linear tetrasaccharide repeating unit, as depicted below. Serological tests indicated that the polymer corresponded to the O24 antigen. -->6)-alpha-D-GlcpNAc-(1-->3)-alpha-L-FucpNAc-(1-->3)-alpha-D-Glcp NAc-(1-->4)-beta-LegpAX-(1-->.

Acinetobacter↗
PubMed1997

Structural and serological characterisation of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter strain 90 belonging to DNA group 10.

Water-soluble lipopolysaccharide (phenol/water extraction) isolated from Acinetobacter strain 90, which belongs to DNA group 10, was hydrolysed with 1% acetic acid, ultracentrifuged, and water-soluble products finally eluted from a Sephadex G-50 column. The major fraction, a polysaccharide, contained D-Gal, D-GlcNAc, D-GalNAc, and 4,6-dideoxy-4-[(R)-3-hydroxybutyramido]-D-galactose (Fuc4NBuOH). The polysaccharide was characterised by means of monosaccharide analyses, Smith-degradation, N-deacetylation/deamination, and NMR studies, and was shown to have a branched pentasaccharide repeating unit. [structure in text] This structure was specifically recognised in western blots and enzyme immunoassays by polyclonal rabbit antisera.

Acinetobacter↗
PubMed1997

Structural and serological characterisation of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter junii strain 65.

A polysaccharide containing rhamnose (Rha) and Gal was isolated by acetic acid hydrolysis, followed by gel-permeation chromatography, from the water-soluble lipopolysaccharide (phenol/water extracted) from Acinetobacter junii strain 65. The polysaccharide was characterised by means of monosaccharide analyses, Smith degradation, and NMR studies, and was shown to have a linear pentasaccharide repeating unit, as depicted below. This structure was specifically recognised in western blots and enzyme immunoassays by polyclonal rabbit antisera. [structure in text]

Acinetobacter↗
PubMed1989

Community-acquired Acinetobacter pneumonia.

We describe the first case report of community-acquired Acinetobacter pneumonia in Australia. Well recognised risk factors for this entity (alcoholism, diabetes mellitus and chronic lung disease) were present in our patient. His pneumonia ran a fulminant course, with death occurring within 24 hours of presentation to hospital. Whilst rare, this infection is being described with increasing frequency, particularly in developing countries including Papua New Guinea.

Acinetobacter Infections↗
PubMed2005

Outer membrane protein 38 of Acinetobacter baumannii localizes to the mitochondria and induces apoptosis of epithelial cells.

Acinetobacter baumannii is an important opportunistic pathogen responsible for nosocomial infection. Despite considerable clinical and epidemiological data regarding the role of A. baumannii in nosocomial infection, the specific virulence factor or pathogenic mechanism of this organism has yet to be elucidated. This study investigated the molecular mechanism of apoptosis on the infection of human laryngeal epithelial HEp-2 cells with A. baumannii and examined the contribution of outer membrane protein 38 (Omp38) on the ability of A. baumannii to induce apoptosis of epithelial cells. A. baumannii induced apoptosis of HEp-2 cells through cell surface death receptors and mitochondrial disintegration. The Omp38-deficient mutant was not as able to induce apoptosis as the wild-type A. baumannii strain. Purified Omp38 entered the cells and was localized to the mitochondria, which led to a release of proapoptotic molecules such as cytochrome c and apoptosis-inducing factor (AIF). The activation of caspase-3, which is activated by caspase-9, degraded DNA approximately 180 bp in size, which resulted in the appearance of a characteristic DNA ladder. AIF degraded chromosomal DNA approximately 50 kb in size, which resulted in large-scale DNA fragmentation. These results demonstrate that Omp38 may act as a potential virulence factor to induce apoptosis of epithelial cells in the early stage of A. baumannii infection.

Acinetobacter baumannii↗
PubMed2004

Morphological changes induced by imipenem and meropenem at sub-inhibitory concentrations in Acinetobacter baumannii.

Abstract Sub-inhibitory concentrations of imipenem and meropenem were evaluated for their ability to induce morphological changes with six strains of Acinetobacter baumannii isolated from patients with nosocomial pneumonia. Three strains were susceptible and three were resistant to carbapenems. The strains were grown in the presence of 0 (controls), 0.25x, 0.5x and 1x the MIC of both carbapenems for 4 h, and then examined after Gram's stain. Cells > or = 3 microm in size (spheroplasts) were considered to be altered. Both carbapenems induced significant numbers of spheroplasts compared to controls. Imipenem had more effect against susceptible strains, while meropenem had a greater effect against resistant strains.

Acinetobacter baumannii↗
PubMed2004

Synergic in-vitro activity of imipenem and sulbactam against Acinetobacter baumannii.

The interaction between sulbactam and imipenem was evaluated with four clinical isolates of Acinetobacter baumannii, including two isolates resistant to imipenem, one of which produced IMP-1 metallo-beta-lactamase. Two isolates (one of which was imipenem-resistant) were sulbactam-resistant by undefined mechanisms. MICs were determined by standard broth microdilution methods. Time-kill assays with imipenem and sulbactam, alone or in combination at 0.5 x MIC and 1 x MIC, showed a synergic effect in all four isolates of A. baumannii after incubation for 0, 4, 8 and > 24 h at 35 degrees C.

Acinetobacter baumannii↗
PubMed2005

The sequences of seven class D beta-lactamases isolated from carbapenem-resistant Acinetobacter baumannii from four continents.

Carbapenem resistance associated with class D beta-lactamases is an increasing problem in Acinetobacter baumannii. Most enzymes of this class reported so far belong to two subgroups, 1 and 2; however, a novel class D carbapenemase (OXA-51) has been reported recently which shares 56% and < 63% amino-acid identity with subgroups 1 and 2, respectively, and which belongs to a third subgroup. This study describes a further seven novel subgroup 3 beta-lactamases in carbapenem-resistant A. baumannii isolates from four continents.

Acinetobacter baumannii↗
PubMed2006

Cephalosporinase over-expression resulting from insertion of ISAba1 in Acinetobacter baumannii.

ISAba1-like sequences were identified immediately upstream of the bla(ampC) gene in ceftazidime-resistant Acinetobacter baumannii isolates, but were absent in ceftazidime-susceptible A. baumannii isolates. AmpC over-expression resulted from insertion of ISAba1-like sequences upstream of bla(ampC). ISAba1 provided strong promoter sequences, and it was demonstrated that the change in the ribosome binding site sequence resulting from insertion of ISAba1 did not influence expression of the bla(ampC) gene. Sequence analysis revealed that AmpC sequences of A. baumannii isolates were almost identical and that ISAba1 elements had a high percentage of identity.

Acinetobacter baumannii↗