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PubMed1996

[Novel site-specific endonuclease from Acinetobacter species M strain].

Site-specific endonuclease R. AspMI was isolated and purified to apparent functional homogeneity from Acinetobacter species (strain M). The enzyme recognizes symmetrical DNA sequence 5'-AGG decreases CCT-3' and cleaves it at the site indicated by the arrow forming blind DNA ends. The endonuclease is an isoschizomer of the StuI endonuclease. Cleavage of the DNA site was inhibited by dcm-methylation. AspMI is approximately equal to 30 kD monomer.

Acinetobacter↗
PubMed1996

Susceptibilities to 23 antimicrobial agents and beta-lactamase production of blood culture isolates of Acinetobacter sp in Hong Kong.

The susceptibility of 140 Acinetobacter spp. isolated from blood cultures of patients from the Prince of Wales Hospital, Hong Kong, from 1990 to 1994 to 23 antimicrobial agents was studied by an agar dilution method. Resistance to most of the beta-lactams, aminoglycosides and fluoroquinolones tested was high, being 11%-92%. Only amikacin, imipenem and meropenem were reliably active against this organism. Most of the isolates produced cephalosporinases with very high pIs while 33% produced beta-lactamases with pI ranges of 5.2-8.7.

Acinetobacter↗
PubMed1996

A comparison of three staining methods in estimation of structures on the cell wall surface of Acinetobacter junii by using electron microscope.

Two strains of Acinetobacter junii isolated from groin and nasal cavity were studied for the presence of structures on the cell wall surface. Three staining methods were used. In the first thin section were contrasted with uranyl acetate and lead citrate. In this method, only electron dense amorphous material could be seen. Using only 1% uranyl acetate, thin fimbriae were observed which in few cases were collected in bundles. Staining with ruthenium red showed bacteria with thick short and long numerous peritrichous structures. Bacteria with structures concentrated near the polar regions were seen as well. From the comparative study of three methods, two of them were found to be useful: methods with ruthenium red and with 1% uranyl acetate.

Acinetobacter↗
PubMed1996

Acinetobacter radioresistens metabolizing aromatic compounds. 1. Optimization of the operative conditions for phenol degradation.

A strain of Acinetobacter radioresistens was able to utilize phenol as the only carbon and energy source, after an acclimatization period of 3 days in which increasing phenol concentrations from 50 to 200 mg/l were supplied. At 30 degrees C, the complete phenol utilization in batch degradation tests occurred in 2.5-3 h at pH 7 and 8, but it increased strongly at pH 6 (over 40 h). No microbial growth was detected at 40 degrees C, while at 20 degrees C (pH 7-8) the time necessary for complete phenol degradation was about twofold longer than that at 30 degrees C (pH 7-8) revealing a good capability of the strain as a seed-micro-organism for enhancing phenol degradation. The bacterial growth in acclimatized cultures, evaluated with the viable cell count, always displayed a trend consistent with the use of phenol as a substrate with an eventual lag phase and then an exponential phase, while in the non-acclimatized cultures an initial stage of cellular death was observed.

Acinetobacter↗
PubMed1997

[The effect of cefepime on ceftazidime, cefotaxime and imipenem resistant strains of Acinetobacter, Xanthomonas, Pseudomonas, Flavobacterium, Sphingobacterium and on producers of extended spectrum beta-lactamases (ESBL) with resistance transfer].

BACKGROUND: The new cephalosporins with heterocyclic positively charged substituent at position C3 belong to the 4th generation cephalosporins. It is not evident, whereas these antibiotics are effective against cefotaxime-ceftazidime-resistant bacteria. We investigated the efficiency of the cefepime (Maxipime, BMS) against Acinetobacter sp., X. maltophilia, Pseudomonas sp., Flavobacterium sp., Sphingobacterium sp. and against strains with production of ESBL (Extended Spectrum beta-Lactamases) (Enterobacter sp., Citrobacter sp., Klebsiella sp.). METHODS AND RESULTS: We determined the susceptibility of the 54 strains resistant to 50 mg/l and more of ceftazidime. The majority of the strains (35) are susceptible to cefepime and MIC is the range 1.65-3.15 mg/l of cefepime. 17 strains have MIC = 6.25 mg/l. Two strains (one strain P. aeruginosa a one strain K. pneumoniae) were resistant to cefepime and MIC = 12.5 mg/l. The activity of beta-lactamases was determined by quantitative macroiodometric method in one strain of P. cepacia and two strains of Sphingobacterium multivorum. They hydrolyse actively imipenem (they produce metallo-beta-lactamase) and ceftazidime (they are highly resistant to this antibiotic), but cefepime is more slowly hydrolysed than ceftazidime. CONCLUSIONS: At the present time cefepime is effective against ceftazidime-resistant strains in so-called "problematic" species of bacteria. However, it is important to protect its efficiency in the future, this requires its rational use.

Acinetobacter↗
PubMed1997

Acinetobacter radioresistens metabolizing aromatic compounds. 2. Biochemical and microbiological characterization of the strain.

The metabolic potentialities of an Acinetobacter radioresistens strain, isolated from the soil adjacent to an activated sludge plant, were investigated. Among 26 aromatic substrates tested, only phenol, benzoate and catechol were metabolized. Since this strain possessed abundant plasmid DNA, the antibiotic and heavy metal resistance was examined, and the bacterial cells proved to be sensitive to all metals (Ni, Tl, Pb, Cd, Ag, Co, Zn) and antibiotics tested except for Fosfomycin and chloramphenicol. The degradation kinetics for phenol and benzoate as the sole carbon/energy source (pH 7, 30 degrees C) displayed different trends, confirmed by the bacterial growth curve. Crude extracts from phenol-grown cultures showed both phenol hydroxylating activity and catechol dioxygenating activity. Phenol hydroxylase possessed a reductase component able to reduce nitroblue tetrazolium (NBT) and cytochrome C, thus exhibiting differences from previously reported monocomponent phenol hydroxylases from the same genus. Catechol dioxygenase is an intradiol-cleaving enzyme recognizing also substituted catechols.

Acinetobacter↗
PubMed1997

Peptide mapping and amino acid sequencing of two catechol 1,2-dioxygenases (CD I1 and CD I2) from Acinetobacter lwoffii K24.

The partial amino acid sequences of two catechol 1,2-dioxygenases (CD I1 and CD I2) from Acinetobacter lwoffii K24 have been determined by analysis of peptides after cleavages with endopeptidase Lys-C, endopeptidase Glu-C, trypsin, and chemicals (cyanogen bromide and BNPS-skatole). They include 248 amino acid sequences (4 fragments) of CD I1 and 211 amino acid sequences (5 fragments) of CD I2. Two enzymes have more than 50% sequence homology with type I catechol 1,2-dioxygenases and less than 30% sequence homology with type II catechol 1,2-dioxygenases. Two enzymes have similar hydropathy profiles in the N-terminal region, suggesting that they have similar secondary structures.

Acinetobacter↗
PubMedDate not supplied

[AccBSI - a novel restriction endonuclease from Acinetobacter calcoaceticus BS].

The recognition site of a new restriction endonuclease from Acinetobacter calcoaceticus BS was determined. This is a nonpalindromic sequence. AccBSI restrictase cleaves DNA chains in the middle of the recognition sequence; therefore, ligation of its digestion fragments restored AccBSI recognition sites and generated palindromic sequences recognized by SacI and SacII restrictases.

Acinetobacter calcoaceticus↗
PubMed1997

Effect of imipenem and sulbactam on sessile cells of Acinetobacter baumannii growing in biofilm.

The effect of the age of biofilms formed by Acinetobacter baumannii on the activity of sulbactam and imipenem on sessile cells was investigated. Against cells of young biofilms both antibiotics were rapidly bactericidal. As the biofilm aged, sulbactam lost most of its activity, but imipenem continued to be bactericidal to some extent. This fact probably reflects the ability of imipenem to exert bactericidal activity on slow-growing bacteria.

Acinetobacter↗
PubMed1976

[Isolation and characterization of rubredoxin from Acinetobacter calcoaceticus].

Acinetobacter calcoaceticus growing on long-chain n-alkanes contains a soluble iron-sulfur protein, which corresponds in its properties to a rubredoxin. It was prepared from the 50000 X g supernatant of ultrasonically treated cells using ion exchange chromatography on DEAE cellulose and gel filtration on Sephadex G-75. The isolated protein is pure electrophoretically, but yields two bands corresponding to molecular weights of 6000 and 12000 respectively. A content of 11 acidic against 6 basic amino acids is in line with the acidic character of the protein. The absence of acid-labile sulfur, content of 4 cysteine residues and one iron atom per polypeptide chain and the typical absorption maxima at gamma = 280, 380, and 490 nm exclude the presence of a ferredoxin. Involvement of the rubredoxin in the alkane hydroxylation is discussed.

Acinetobacter↗
PubMed1975

[Inhibition of the malic enzyme from Acinetobacter calcoaceticus by NADPH and NADH].

The malic enzyme enriched from Acinetobacter calcoaceticus is inhibited by NADPH and NADH. The inhibition afforded by the reduced coenzymes is not affected by NAD+, AMP and 3'.5'-AMP. Against L-malate, NADPH inhibits the enzyme in a noncompetitive linear fashion (Ki = 1.5 x 10(-4) M), against NADP+, competitively linearly (Ki = 5.0 x 10(-5) M). While NADPH acted as a product inhibitor, NADH seems to be an allosteric effector of the malic enzyme, because with L-malate as the variable substrate in the double reciprocal plot, a nonlinear curve is obtained.

Acinetobacter↗
PubMed1998

Electron-microscopic observation of adherence of Acinetobacter baumannii to red blood cells.

It is now recognized that Acinetobacter spp. play a significant role in the colonization and infection of patients admitted to hospitals. The virulence factors of A. baumannii remains largery unknown. In this study, the adherence of A. baumannii to several species of red blood cells was investigated. The ruthenium red staining was used for electron microscopic studies. The results obtained in electron microscopy and the hemagglutination studies suggested that the thin and long fimbriae of A. baumannii participated in adhesion of these bacteria to red blood cells.

Acinetobacter↗
PubMed1998

[Utilization of siderophores from the Acinetobacter genus by staphylococcal bacilli].

The ability of iron utilizing by means of siderophores produced by donor strains--the members of the genus Acinetobacter (8 strains) by 24 staphylococcal strains was investigated. All the donor strains synthesized hydroxamate class siderophores and six strains also catecholate class. The majority of staphylococcal strains could utilize these siderophores. Most strains utilized siderophores from A. juni 321 and A. johnsonii 349 strains. Only three staphylococcal strains were not be able to utilize siderophores from all donor strains.

Acinetobacter↗
PubMed1998

Adherence of Acinetobacter baumannii to rat bladder tissue.

Acinetobacter baumannii, an important nosocomial pathogen, causes severe infections in patients of intensive care units, but its pathogenic attributes are unknown. Previously, the adherence of A. baumannii to cell lines has been negative in the authors' laboratory. In this work, the adherence of strains of A. baumannii of various biotypes to small pieces of rat bladder tissue was investigated. Tissue pieces were submerged into cultures of A. baumannii and sessile cells were counted after removing planktonic bacteria. Fimbriae and sessile cells were examined by transmission and scanning electron microscopy, respectively. In contrast to a uropathogenic strain of Escherichia coli, all cultures exhibited a mannose- and galactose-resistant agglutination of human group O red blood cells as well as mannose- and galactose-resistant adherence to the bladder tissue. Inhibition of exopolysaccharide synthesis did not modify adherence. Indeed, adherence, apparently unrelated to these fimbriae or to the exopolysaccharide, may be a factor contributing to the pathogenicity of A. baumannii in the urinary tract or in other tissues.

Acinetobacter↗
PubMed1999

In vitro effect of imipenem on Acinetobacter baumannii.

Imipenem at suprainhibitory concentrations (2x, 4x or 8x MIC) induced postantibiotic effects (PAEs) (suppression of bacterial growth after a short time exposure of bacteria to antimicrobials) against two of three Acinetobacter baumannii strains. The highest concentration tested demonstrated the longest delay of bacterial regrowth (1.7 h (strain 5570) or 3.9 h (strain 6070)). All. A. baumannii strains showed changes in surface hydrophobicity and serum sensitivity after treatment with imipenem. The antibiotic at 8x MIC reduced hydrophobicity of the strains most significantly (from 42.3%-72.0%) as compared to controls (without antibiotic). Susceptibility of the treated bacteria to serum bactericidal activity has also been lowered. Though imipenem suppressed bacterial growth and decreased surface hydrophobicity of the bacteria, it increased survival of bacteria after incubation with serum. These different alterations observed in the studied strains should be taken into account when evaluating the effects of imipenem.

Acinetobacter↗
PubMed1999

Isolation and characterization of heat-modifiable proteins from the outer membrane of Porphyromonas asaccharolytica and Acinetobacter baumannii.

Active porins were isolated and purified from the outer membranes of the gram-negative anaerobic rod Porphyromonas asaccharolytica and the aerobic coccobacillus Acinetobacter baumannii. The porins from both bacteria appear to be monomers when isolated and purified. Both porins exhibited decreased mobility on SDS-PAGE after boiling for 10 min in the sample buffer. After heating, their molecular weight is estimated at 43 kDa while without heating they run as proteins with a molecular weight of approximately 37 kDa. Due to their characteristic heat-modifiability, these proteins were named HMP (heat-modifiable protein)-P. asaccharolytica and HMP-A. baumannii. Amino acid analysis revealed both porins to be hydrophilic proteins. These proteins have been shown to be active in transporting sugars when incorporated into liposomes. The permeability of both porins for L-arabinose was less than that produced by the porin of Escherichia coli B. Permeability to high molecular weight disaccharides was lower than for small monosaccharides. Western blot analysis did not reveal any antigenic cross reaction between HMP-A. baumannii and the HMP-P. asaccharolytica. The results obtained in this study confirm that although these heat-modifiable proteins are pore forming proteins and have similar activity they differ in their antigenicity.

Journal Article↗
PubMed2026

Carbapenemase-producing Acinetobacter baumannii from Spanish hospitals, 2016-2020: Interregional spread of ST2PAS isolates co-harbouring blaOXA-23, blaOXA-66 and armA genes.

INTRODUCTION AND AIMS: Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a serious global threat, prioritized by the World Health Organization for new antibiotic development. The European Centre for Disease Prevention and Control proposed the integration of genomic sequencing into surveillance. This study characterizes phenotypic and genotypic features of nationwide-collected CRAB isolates from Spanish hospitals (2016-2020). MATERIALS AND METHODS: A total of 822 CRAB isolates sent to the Spanish reference laboratory were analysed, and 108 representative isolates were selected from 48 hospitals in 25 Spanish provinces. Antibiotic susceptibility was determined according to European Committee on Antimicrobial Susceptibility Testing guidelines, and WGS was performed by Illumina. Resistome, virulome, phylogeny (core-genome Multi-Locus Sequence-Typing; 2390 genes), insertion sequences and plasmids were analysed. RESULTS: Of the 108 representative isolates, 68.5% produced OXA-23, 10.2% OXA-24, 7.4% OXA-58, 1.9% NDM-1 and 2.7% others. 3.7% co-produced two acquired carbapenemases, and six that did not have them showed the ISAba1 upstream of the blaOXA-51 like. The predominant sequence types were ST2pas (82.4%) and ST218Oxf (61.1%). blaOXA-66 chromosomal carbapenemase allele was present in 75% of the 108 isolates, armA 16 s rRNA methyltransferase gene in 61.1%, and the kL-7/OCL-18 was present in 59.3% of the isolates. The most active antibiotic was colistin. Overall, 65.4% of invasive cases were caused by isolates harbouring all 38 virulence genes tested. In 64.8% of isolates a plasmid type was detected, mainly pS32-1-like (54.6%). CONCLUSIONS: In Spain, CRAB dissemination is driven by interregional spread of isolates belonging to the ST218Oxf/ST2Pas clones, characterized by the blaOXA-23/blaOXA-66 genotype, the presence of armA, the KL7/OCL18 capsular profile and the presence of pS32-1 plasmid.

K Locus↗
PubMed1999

Differential organization and transcription of the cat2 gene cluster in aniline-assimilating Acinetobacter lwoffii K24.

CatABC genes encode proteins that are responsible for the first three steps of one branch of the beta-ketoadipate pathway involved in the degradation of various aromatic compound by bacteria. Aniline-assimilating Acinetobacter lwoffii K24 is known to have the two-catABC gene clusters (cat1 and cat2) on the chromosome (Kim et al., J. Bacteriol., 179: 5226-5231, 1997). The order of the cat2 gene cluster is catB2A2C2, which has not been found in other bacteria. In this report, we analyzed the transcriptional pattern of the cat2 gene cluster and completely sequenced a 5.8 kbp fragment containing the compactly clustered catB2A2C2 genes and four ORFs. Similar to the ORF(R1) of the cat1 gene cluster, an ORF highly homologous with the catR gene was found 102 by upstream of the catB2 gene and was designated as ORF(R2). Three ORFs, one putative reductase component (ORF(X2)) and two putative LysR family regulatory proteins (ORF(Y2), ORF(Z2)) were located next to the catC2 gene in the opposite direction of the cat2 gene cluster. Two ORFs, ORF(X2) and ORF(Y2), were significantly homologous with tdnB and tdnR of the aniline oxygenase complex of Pseudomonas putida UCC22. RT-PCR analysis and Northern blotting revealed that the catB2 gene is independently transcribed and that the catA2C2 genes are cotranscribed. A primer extension assay revealed that transcription of the catA2C2 gene starts in the C-terminal region of the catB2 gene. These results suggest that the cat2 gene cluster may be under a different gene adaptation from other cat gene clusters.

Journal Article↗