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PubMedDate not supplied

Transverse myelitis associated with Acinetobacter baumanii intrathecal pump catheter-related infection.

OBJECTIVE: To describe a late neurologic complication of intrathecal pump implantation and show the methods used for the diagnosis and successful treatment of transverse myelitis in this setting. CASE REPORT: A 32-year-old man with a chronic abdominal pain syndrome presented with right lower-extremity numbness 2 months after the placement of an intrathecal morphine pump. This progressed to bilateral lower extremity and ascending sensory loss to T12-L1 dermatome, significant lower-extremity weakness, constipation with overflow incontinence, and detrusor instability causing urinary incontinence in discrete episodes over the following 2 months consistent with a myelopathy. Magnetic resonance imaging (MRI) of the thoracic spine and cerebrospinal fluid (CSF) analysis were consistent with transverse myelitis. The intrathecal pump was removed and an Acinetobacter baumanii catheter-tip infection was diagnosed. Clinical course improved with the co-administration of intravenous corticosteroids and antibiotics, with significant clinical improvement within 30 days. CONCLUSIONS: Clinicians should recognize transverse myelitis as a possible late complication of intrathecal pump placement. Early medical intervention and removal of the intrathecal pump may be necessary to prevent irreversible spinal cord damage and may support good recovery.

Acinetobacter Infections↗
PubMed2006

Low genetic diversity of the intrinsic OXA-51-like class D carbapenemases among Acinetobacter baumannii clinical isolates in Greece.

This study examined the geographical distribution and diversity of the intrinsic OXA-51-like class D carbapenemases among Acinetobacter baumannii clones recovered in three major Greek regions from 2000 to 2005. The blaOXA-66 allele was exclusively detected among clonally distinct A. baumannii isolates recovered in the regions of Thessaloniki and Larissa. This sequence was also the most widespread among A. baumannii isolates in Athens, while less frequent were blaOXA-69 and blaOXA-65 alleles. These findings highlight the high prevalence of a specific blaOXA-51-like allele in Greece, possibly indicating that our A. baumannii clones might have originated from a common ancestor. However, the possibility that blaOXA-51-like variants, with blaOXA-66 predominating, are widely disseminated among several unrelated A. baumannii strains cannot be excluded.

Acinetobacter baumannii↗
PubMed1987

Effect of plasmid RP1 on phase changes in inner and outer membranes and lipopolysaccharide from Acinetobacter calcoaceticus: a Fourier transform infrared study.

The successful transfer of the resistance plasmid RP1 into the Gram-negative bacterium Acinetobacter calcoaceticus resulted in increased resistance of this microorganism to the antibiotics kanamycin and tetracycline. Microorganisms harboring the RP1 plasmid showed altered fatty acid composition in the lipopolysaccharide fraction and increased outer membrane permeability compared to organisms without the plasmid. Thermotropic gel to liquid crystal lipid phase changes were detected in both inner and outer membranes and purified lipopolysaccharide by Fourier transform infrared spectroscopy. The phase transition temperatures observed in the outer membranes and isolated lipopolysaccharide of the plasmid-containing cells were significantly higher than those of the plasmid-free organisms, while little difference was observed for the inner membranes. The plasmid-induced decrease in outer membrane fluidity may play a mediating role in the mechanisms of antibiotic resistance and susceptibility to host immune cells in Gram-negative microorganisms.

Acinetobacter↗
PubMed1989

Quinoprotein D-glucose dehydrogenase of the Acinetobacter calcoaceticus respiratory chain: membrane-bound and soluble forms are different molecular species.

Acinetobacter calcoaceticus is known to contain soluble and membrane-bound quinoprotein D-glucose dehydrogenases, while other oxidative bacteria contain the membrane-bound enzyme exclusively. The two forms of glucose dehydrogenase were believed to be the same enzyme or interconvertible forms. Previously, Matsushita et al. [(1988) FEMS Microbiol. Lett 55, 53-58] showed that the two enzymes are different with respect to enzymatic and immunological properties, as well as molecular weight. In the present study, we purified both enzymes and compared their kinetics, reactivity with ubiquinone homologues, and immunological properties in detail. The purified membrane-bound enzyme had a molecular weight of 83,000, while the soluble form was 55,000. The purified enzymes exhibited totally different enzymatic properties, particularly with respect to reactivity toward ubiquinone homologues. The soluble enzyme reacted with short-chain homologues only, whereas the membrane-bound enzyme reacted with long-chain homologues including ubiquinone 9, the native ubiquinone of the A. calcoaceticus. Furthermore, the two enzymes were distinguished immunochemically; the membrane-bound enzyme did not cross-react with antibody raised against the soluble enzyme, nor did the soluble enzyme cross-react with antibody against the membrane-bound enzyme. Thus, each glucose dehydrogenase is a molecularly distinct entity, and the membrane-bound enzyme only is coupled to the respiratory chain via ubiquinone.

Acinetobacter↗
PubMed1978

Amino acid sequence of the diazooxonorleucine binding site of Acinetobacter and Pseudomonas 7A glutaminase--asparaginase enzymes.

Acinetobactor glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine, reduced with sodium borohydride, and cleaved with cyanogen bromide. Radioactivity was present only in a 96-residue-N-terminal peptide which eluted as the second peptide peak on Sephadex G-50. Radioactivity was released with the threonine in position 12 during automatic sequencing of this peptide. The amino acid sequence of a 60-residue tn-terminal segment and a 16-residue C-terminal segment of this peptide was determined. Pseudomonas 7 A glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine and reduced with sodium borohydride. Radioactivity was released with the threonine in residue 20 during automatic sequencing of the whole enzyme. Analysis of 26 N-terminal residues showed that an 8-residue segment containing the radioactive threonine was identical with that in Acinetobacter glutaminase-asparaginase and in Escherichia coli asparaginase. Additional identical residues were noted in the N-terminal regions of these enzymes.

Acinetobacter↗
PubMed2005

The reductase of p-hydroxyphenylacetate 3-hydroxylase from Acinetobacter baumannii requires p-hydroxyphenylacetate for effective catalysis.

p-Hydroxyphenylacetate (HPA) hydroxylase (HPAH) from Acinetobacter baumannii catalyzes hydroxylation of HPA to form 3,4-dihydroxyphenylacetate. It is a two-protein system consisting of a smaller reductase component (C(1)) and a larger oxygenase component (C(2)). C(1) is a flavoprotein containing FMN, and its function is to provide reduced flavin for C(2) to hydroxylate HPA. We have shown here that HPA plays important roles in the reaction of C(1). The apoenzyme of C(1) binds to oxidized FMN tightly with a K(d) of 0.006 microM at 4 degrees C, but with a K(d) of 0.038 microM in the presence of HPA. Reduction of C(1) by NADH occurs in two phases with rate constants of 11.6 and 3.1 s(-)(1) and K(d) values for NADH binding of 2.1 and 1.5 mM, respectively. This result indicates that C(1) exists as a mixture of isoforms. However, in the presence of HPA, the reduction of C(1) by NADH occurred in a single phase at 300 s(-)(1) with a K(d) of 25 microM for NADH binding at 4 degrees C. Formation of the C(1)-HPA complex prior to binding of NADH was required for this stimulation. The redox potentials indicate that the rate enhancement is not due to thermodynamics (E degrees (m) of the C(1)-HPA complex is -245 mV compared to an E degrees (m) of C(1) of -236 mV). When the C(1)-HPA complex was reduced by 4(S)-NADH, the reduction rate was changed from 300 to 30 s(-)(1), giving a primary isotope effect of 10 and indicating that C(1) is specifically reduced by the pro-(S)-hydride. In the reaction of reduced C(1) with oxygen, the reoxidation reaction is also biphasic, consistent with reduced C(1) being a mixture of fast and slow reacting species. Rate constants for both phases were the same in the absence and presence of HPA, but in the presence of HPA, the equilibrium shifted toward the faster reacting species.

Acinetobacter baumannii↗
PubMedDate not supplied

Recovery of Acinetobacter radioresistens lipase by hydrophobic adsorption to n-hexadecane coated on nonwoven fabric.

A simple and clean adsorption/desorption process was proposed for recovering Acinetobacter radioresistens lipase from fermentation broth. The adsorbent used was n-hexadecane coated on a hydrophobic nonwoven fabric (NWF). n-Hexadecane has a melting point of 16-18 degrees C, and its affinity for lipase decreases markedly from liquid to solid state. Accordingly, performing the adsorption and desorption above and below, respectively, the melting point would need no extraneous materials for separation. The adsorption isotherms at various temperatures were found to follow the Langmuir model. Simulation of the batch adsorption/desorption process showed that there exists an optimal amount of adsorbent for both concentration factor and enzyme recovery; the process is restrained by equilibrium. The performance of column adsorption/desorption could also be simulated using the adsorption isotherm, and it was shown that the concentration factor was proportional to the amount of adsorbent used. The benefits of this process include easy preparation of adsorbent, low operational cost, no extraneous materials needed, negligible enzyme denaturation, high efficiency, and simple process simulation.

Acinetobacter↗
PubMedDate not supplied

Highly efficient conversion of lactate to pyruvate using whole cells of Acinetobacter sp.

On an industrial scale, the production of pyruvate at a high concentration from the cheaper lactate substrate is a valuable process. To produce pyruvate from lactate by whole cells, various lactate-utilizing microorganisms were isolated from soil samples. Among them, strain WLIS, identified as Acinetobacter sp., was screened as a pyruvate producer. For the pyruvate preparation from lactate, the preparative conditions were optimized with whole cells of the strain. The cells cultivated in the medium containing 100 mM of l-lactate showed the highest biotransformation efficiency from lactate to pyruvate. The optimized dry-cell concentration, pH, and temperature of reaction were 6 g/L, pH 7.0-7.5, and 30 degrees C, respectively. The influences of ethylenediaminetetraacetic acid (EDTA) and aeration on a biotransformation reaction were carried out under the test conditions. Under the optimized reaction conditions, l-lactate at concentrations of 200 and 500 mM were almost totally stoichiometrically converted into pyruvate in 8 and 12 h, respectively. About 60% of 800 mM of l-lactate was transformed into pyruvate in 24 h. This reduced conversion rate is probably due to the high substrate inhibition in biotransformation.

Acinetobacter↗
PubMedDate not supplied

Identification of an OprD homologue in Acinetobacter baumannii.

With the increased number of resistant Acinetobacter baumannii strains, it is urgently required to decipher the molecular bases of outer membrane permeability. The analyses of the outer membrane from different A. baumannii strains indicated a modification in the expression of two proteins of 29 and 43 kDa, respectively. By electrophoresis and MALDI-MS analyses, the 43 kDa OMP was identified as a protein belonging to the OprD family, a basic amino acid and imipenem porin.

Acinetobacter baumannii↗
PubMed2006

Global comparison of the membrane subproteomes between a multidrug-resistant Acinetobacter baumannii strain and a reference strain.

Acinetobacter baumannii causes severe infections in compromised patients. We combined SDS-PAGE, two-dimensional gel electrophoresis and mass spectrometry (LC-MS/MS and MALDI-TOF) to separate and characterize the proteins of the cell envelope of this bacterium. In total, 135 proteins (inner and outer membrane proteins) were identified. In this analysis, we described the expression by this bacterium of RND-type efflux systems and some potential virulence factors. We then compared the membrane subproteome of a clinical multidrug-resistant (MDR) isolate with that of a reference strain. We found that the MDR strain expressed lower levels of the penicillin-binding-protein 1b, produced a CarO protein having different primary and quaternary structures to that of the reference strain, and expressed OmpW isoforms. We also showed that the clinical strain has a high ability to form biofilms consistent with the accumulation of some outer membrane proteins (OMPs) such as NlpE or CsuD that have already been described as involved in bacterial adhesion. These features may partly explain the MDR emergence of the clinical isolate.

Acinetobacter baumannii↗
PubMed1999

Purification and properties of pyrophosphatase of Acinetobacter johnsonii 210A and its involvement in the degradation of polyphosphate.

Inorganic pyrophosphatase (E.C. 3.6.1.1) of Acinetobacter johnsonii 210A was purified 200-fold to apparent homogeneity. The enzyme catalyzed the hydrolysis of inorganic pyrophosphate and triphosphate to orthophosphate. No activity was observed with other polyphosphates and a wide variety of organic phosphate esters. The molecular mass of the enzyme was estimated to be 141 kDa by gelfiltration. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a subunit composition of six identical polypeptides with a molecular mass of 23 kDa. The cation Mg2+ was required for activity, the activity with Mn2+, Co2+ and Zn2+ was 48, 48 and 182% of the activity observed with Mg2+, respectively. The enzyme was heat-stable and inhibited by fluoride and iodoacetamide. The analysis of the kinetic properties of the enzyme revealed an apparent Km for pyrophosphate of 0.26 mM. In A. johnsonii 210A, pyrophosphatase may be involved in the degradation of high-molecular polyphosphates under anaerobic conditions: (i) it catalyses the further hydrolysis of pyrophosphate and triphosphate formed from high-molecular weight polyphosphates by the action of exopolyphosphatase, and (ii) it abolishes the inhibition of polyphosphate: AMP phosphotransferase-mediated degradation by pyrophosphate and triphosphate.

Acinetobacter↗
PubMed2001

Phosphate uptake and release by Acinetobacter johnsonii in continuous culture and coupling of phosphate release to heavy metal accumulation.

A strain of polyphosphate-synthesizing, phosphate-releasing Acinetobacter johnsonii was isolated from a wastewater treatment plant operating enhanced biological phosphate removal (EBPR) and was used to remove La(3+) from solution via precipitation of cell-bound LaPO(4). The effect of repeated aerobic-anaerobic cycles on the carbon and phosphate metabolism of the organism was studied in attempts to promote increased phosphate flux using a three-stage, continuous bioreactor comprising aerobic, anaerobic and settling vessels. The bioreactor was operated in two modes: In flow-through mode, cells were grown aerobically with acetate as the sole carbon source, promoting excess phosphate uptake (up to 5.0 mmol/l=3.0 mmol/g protein). Cells were diluted into the anaerobic vessel where phosphate was released (up to 1.0 mmol/l=0.3 mmol/g protein), and thence to waste. The system was initially operated to steady state in flow-through mode, then switched to recycle mode. Here the anaerobic vessel output passed to a settling vessel from which settled cells were returned to the aerobic vessel. Carbon source (acetate) was supplied only to the anaerobic vessel; increased anaerobic acetate uptake was observed during recycle, which was sustained when the system was returned to flow-through mode and was related to increased cellular lipid inclusions by flow cytometry and electron microscopy. These phenomena may represent adaptation of cells to aerobic-anaerobic cycling with aerobic carbon/energy limitation. Addition of La(3+) to the anaerobic vessel during recycle mode promoted removal of 95% of the La(3+) from a 0.1 to 0.3 mM (14-42 ppm) solution at the expense of biogenic phosphate.

Acetates↗
PubMed1975

The aerobic metabolism of cyclohexanecarboxylic acid by Acinetobacter anitratum.

1. The aerobic metabolism of cyclohexanecarboxylic acid by a bacterium isolated from garden soil (Acinetobacter anitratum) was investigated. 2. Evidence for the formation of cyclohex-1-ene-1-carboxylate, 2-hydroxycyclohexanecarboxylate and pimelate when either cell suspensions or cell-free extracts were incubated in the presence of cyclohexanecarboxylic acid is presented. 3. Crude cell-free extracts required ATP, CoA, FAD and Mg2+ as cofactors for the production of pimelate from cyclohexanecarboxylic acid, suggesting the existence of an activating reaction with formation of CoA esters, in this system.

Acinetobacter↗
PubMed2003

Acetylacetone-cleaving enzyme Dke1: a novel C-C-bond-cleaving enzyme from Acinetobacter johnsonii.

The toxicity of acetylacetone has been demonstrated in various studies. Little is known, however, about metabolic pathways for its detoxification or mineralization. Data presented here describe for the first time the microbial degradation of acetylacetone and the characterization of a novel enzyme that initiates the metabolic pathway. From an Acinetobacter johnsonii strain that grew with acetylacetone as the sole carbon source, an inducible acetylacetone-cleaving enzyme was purified to homogeneity. The corresponding gene, coding for a 153 amino acid sequence that does not show any significant relationship to other known protein sequences, was cloned and overexpressed in Escherichia coli and gave high yields of active enzyme. The enzyme cleaves acetylacetone to equimolar amounts of methylglyoxal and acetate, consuming one equivalent of molecular oxygen. No exogenous cofactor is required, but Fe(2+) is bound to the active protein and essential for its catalytic activity. The enzyme has a high affinity for acetylacetone with a K (m) of 9.1 microM and a k(cat) of 8.5 s(-1). A metabolic pathway for acetylacetone degradation and the putative relationship of this novel enzyme to previously described dioxygenases are discussed.

Acetates↗
PubMed1983

Mutant strains of Acinetobacter calcoaceticus possessing additional mandelate dehydrogenases. Identification and preliminary characterization of the enzymes.

Acinetobacter calcoaceticus wild-type strain N.C.I.B. 8250 can grow on only the L(+)-isomer of mandelate but mutant strains have been isolated that can grow on D(-)-mandelate. These mutants contain a novel D(-)-mandelate dehydrogenase in addition to the original L(+)-mandelate dehydrogenase. A second wild-type strain, EBF 65/65, shows the opposite pattern and can grow on D(-)-mandelate but not on L(+)-mandelate; mutants have been isolated that possess an L(+)-mandelate dehydrogenase in addition to the original D(-)-mandelate dehydrogenase and can thus grow on L(+)-mandelate. Both L(+)- and D(-)-mandelate dehydrogenases, whether originally present or evolved, are very similar in many respects: they are membrane-bound and NAD(P)+-independent; their activities have similar dependence on temperature and pH; they are inhibited by oxalate but not by several metal-chelating agents; they are stereospecific in their action and are inhibited by the opposite stereoisomers. D(-)-Mandelate dehydrogenase is much more susceptible than L(+)-mandelate dehydrogenase to inhibition by HgCl2 and p-chloromercuribenzoate and is much more heat-labile.

Acinetobacter↗
PubMed1985

Membrane-bound lactate dehydrogenases and mandelate dehydrogenases of Acinetobacter calcoaceticus. Location and regulation of expression.

Acinetobacter calcoaceticus possesses an L(+)-lactate dehydrogenase and a D(-)-lactate dehydrogenase. Results of experiments in which enzyme activities were measured after growth of bacteria in different media indicated that the two enzymes were co-ordinately induced by either enantiomer of lactate but not by pyruvate, and repressed by succinate or L-glutamate. The two lactate dehydrogenases have very similar properties to L(+)-mandelate dehydrogenase and D(-)-mandelate dehydrogenase. All four enzymes are NAD(P)-independent and were found to be integral components of the cytoplasmic membrane. The enzymes could be solubilized in active form by detergents; Triton X-100 or Lubrol PX were particularly effective D(-)-Lactate dehydrogenase and D(-)-mandelate dehydrogenase could be selectively solubilized by the ionic detergents cholate, deoxycholate and sodium dodecyl sulphate.

Acinetobacter↗
PubMed1985

Membrane-bound lactate dehydrogenases and mandelate dehydrogenases of Acinetobacter calcoaceticus. Purification and properties.

Procedures were developed for the optimal solubilization of D-lactate dehydrogenase, D-mandelate dehydrogenase, L-lactate dehydrogenase and L-mandelate dehydrogenase from wall + membrane fractions of Acinetobacter calcoaceticus. D-Lactate dehydrogenase and D-mandelate dehydrogenase were co-eluted on gel filtration, as were L-lactate dehydrogenase and L-mandelate dehydrogenase. All four enzymes could be separated by ion-exchange chromatography. D-Lactate dehydrogenase and D-mandelate dehydrogenase were purified by cholate extraction, (NH4)2SO4 fractionation, gel filtration, ion-exchange chromatography and chromatofocusing. The properties of D-lactate dehydrogenase and D-mandelate dehydrogenase were similar in several respects: they had relative molecular masses of 62 800 and 59 700 respectively, pI values of 5.8 and 5.5, considerable sensitivity to p-chloromercuribenzoate, little or no inhibition by chelating agents, and similar responses to pH. Both enzymes appeared to contain non-covalently bound FAD as cofactor.

Acinetobacter↗
PubMed1986

Purification and characterization of quinoprotein glucose dehydrogenase from Acinetobacter calcoaceticus L.M.D. 79.41.

Quinoprotein glucose dehydrogenase (EC 1.1.99.17) from Acinetobacter calcoaceticus L.M.D. 79.41 was purified to homogeneity. It is a basic protein with an isoelectric point of 9.5 and an Mr of 94,000. Denaturation yields two molecules of PQQ/molecule and a protein with an Mr of 48000, indicating that the enzyme consists of two subunits, which are probably identical because even numbers of aromatic amino acids were found. The oxidized enzyme form has an absorption maximum at 350 nm, and the reduced form, obtained after the addition of glucose, at 338 nm. Since double-reciprocal plots of initial reaction rates with various concentrations of glucose or electron acceptor show parallel lines, and substrate inhibition is observed for glucose as well as for electron acceptor at high concentrations, a ping-pong kinetic behaviour with the two reactants exists. From the plots, Km values for glucose and Wurster's Blue of 22 mM and 0.78 mM respectively, and a Vmax. of 7.730 mumol of glucose oxidized/min per mg of protein were derived. The enzyme shows a broad substrate specificity for aldose sugars. Cationic electron acceptors are active in the assay, anionic acceptors are not. A pH optimum of 9.0 was found with Wurster's Blue and 6.0 with 2,6-dichlorophenol-indophenol. Two types of quinoprotein glucose dehydrogenases seem to exist: type I enzymes are acidic proteins from which PQQ can be removed by dialysis against EDTA-containing buffers (examples are found in Escherichia coli, Klebsiella aerogenes and Pseudomonas sp.); type II enzymes are basic proteins from which PQQ is not removed by dialysis against EDTA-containing buffers (examples are found in A. calcoaceticus and Gluconobacter oxydans).

Acinetobacter↗