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PubMed1998

Characterization of oligonucleotide probes for the identification of Acinetobacter spp., A. baumannii and Acinetobacter genomic species 3.

The 16S-23S intergenic spacer regions of four Acinetobacter genomic species belonging to the A. calcoaceticus-A. baumannii (Acb) complex, i.e. genomic species 1 (A. calcoaceticus), genomic species 2 (A. baumannii), genomic species 3 and Tjernberg and Ursing (TU) genomic species 13, have been cloned and sequenced. Sequence analysis led to the discovery of a single copy of IIe and Ala tRNA genes within each spacer. Sequence comparison allowed the identification of a 192-base-pair long highly conserved sequence between the 3' end of the 16S rRNA and the 5' end of the tRNA(Ala) genes. Moreover, two short regions, which were specific to, respectively, genomic species 2 and 3, could be identified. Oligonucleotides corresponding to these sequences were constructed and tested for the ability to hybridize with chromosomal DNA extracted from Acinetobacter belonging to different genomic species and with chromosomal DNA of other bacterial genera. One of these oligonucleotides was demonstrated to be useful as a sensitive and specific probe for A. baumannii. A less sensitive probe for Acinetobacter genomic species 3 was also developed.

Acinetobacter↗
PubMed1998

Cloning and characterization of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) transferase genes (kdtA) from Acinetobacter baumannii and Acinetobacter haemolyticus.

3-Deoxy-D-manno-oct-2-ulosonic acid (Kdo) transferases (KdtA) are multifunctional glycosyltransferases with primary structures of low similarity. Totally degenerated primers were deduced from two stretches of identical amino acids between known KdtA sequences and used to amplify by PCR a kdtA-specific fragment from Acinetobacter baumannii ATCC 15308 DNA which was then applied as a probe for the cloning and sequencing of the complete Kdo transferase gene. With conserved PCR primers for this structural gene from A. baumannii ATCC 15308, also kdtA genes of A. baumannii ATCC 19606 and A. haemolyticus ATCC 17906 were obtained, cloned from the chromosome and sequenced. The genes coded for proteins with similarities to known Kdo transferases. Within the genus Acinetobacter, the identity and similarity of the deduced amino acid sequences were 71% and 84.5%, respectively. The kdtA sequences of both A. baumannii strains were identical and possessed a TTG start codon, whereas ATG was found in the case of A. haemolyticus. The genes from Acinetobacter and kdtA from Escherichia coli K-12 were expressed in the Gram-positive bacterium Corynebacterium glutamicum. In vitro tests confirmed the function of the gene products as Kdo transferases, which transferred mainly two Kdo residues to a synthetic lipid A precursor of E. coli. Also, no differences between the cloned kdtA genes from A. baumanniii, A. haemnolyticus and E. coli were observed when tetraacyl or hexaacyl lipid A were tested, since all transferases acted more efficiently on the former. With limiting amounts of acceptor, all Kdo transferases were able to transfer a third Kdo residue with varying efficiency.

Acinetobacter↗
PubMed1990

[Spontaneous transformation in mixed cultures of various types of Acinetobacter and during joint growth of Acinetobacter calcoaceticus with Escherichia coli and Pseudomonas aeruginosa].

The transfer of chromosomal and plasmid genes was studied via spontaneous transformation is mixed cultures of Acinetobacter spp. It turned out that any Acinetobacter strain, irrespective of its species specificity, serves as chromosomal DNA donor in case the mixed culture contains competent cells of the recipient strain. No transfer took place when non-related bacteria were used as donors. We also studied the transfer into Ac. calcoaceticus competent strain cells of small non-conjugative plasmids having broad host range (RSF1010, pAK1). In these cases, DNA donors could be not only acinetobacters of other species, but bacteria belonging to other systematic groups (families)--E. coli and P. aeruginosa. The transfer of plasmids from cells of unrelated bacteria took place with a frequency of about 10(-5)-10(-6). The possible role of spontaneous transformation in horizontal gene transfer is discussed.

Acinetobacter↗
PubMed1997

Use of different PCR-based DNA fingerprinting techniques and pulsed-field gel electrophoresis to investigate the epidemiology of Acinetobacter calcoaceticus-Acinetobacter baumannii complex.

Acinetobacter calcoaceticus-Acinetobacter baumannii complex is an important nosocomial pathogen for which optimal typing methods in epidemiologic investigations have not been defined. We compared DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) with different PCR-based DNA fingerprinting techniques, including enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR), repetitive extragenic palindromic (REP) PCR, arbitrary-primed PCR with primer M13, and multiplex PCR with primers REP-1, REP-2 and M13, for characterization of 98 clinical isolates (including 10 apparent outbreak-related isolates and 68 presumed epidemiologically unrelated isolates) in a tertiary-care hospital over a 4-year period. The PFGE patterns after Smal restriction of the bacterial DNA were analyzed by computer software (Gelcompar) using the unweighted pair group method with arithmetic averages clustering and the Dice coefficient. A cluster of 48 isolates (cluster A), including 9 outbreak isolates, linked at a level of 83.4% similarity was observed. This epidemic strain and its variants were also found among the 68 presumed epidemiologically unrelated isolates, and this may represent ongoing endemic infection in this institution. The discrimination index for the PCR-based DNA fingerprinting techniques was 0.75 for enterobacterial repetitive intergenic consensus 1, 0.71 for M13, 0.77 for REP-1, 0.77 for REP-2, and 0.87 for multiplex PCR. The discriminatory power of PFGE was found to be higher than those of PCR-based techniques. It was concluded that both PFGE and PCR-based fingerprinting are useful for typing of A. calcoaceticus-A. baumannii complex. However, PFGE can detect minor mutations among outbreak strains, and this is important for epidemiological study of this species in a complex endemic setting.

Acinetobacter↗
PubMed2000

Examination of polyclonal rabbit immune sera against serovars of Acinetobacter baumannii and genospecies 3 for cross-reactions with reference strains of other named/unnamed genospecies of Acinetobacter.

Polyclonal rabbit immune sera against 38 serovars of Acinetobacter baumannii and genospecies 13 capable of growth at 44 degrees C and against 26 serovars of genospecies 3 and genospecies 13 incapable of growth at 44 degrees C were examined for serological cross-reactivity with reference strains comprising 17 genospecies (among them 6 named species) of Acinetobacter. Checkerboard agglutination tests yielded very few cross-reactions. Specifically, genospecies 17 cross-reacted weakly with A. baumannii serovar 27; strains genospecies 13 (Bouvet), TU 14, and 'close to TU 13' were strongly agglutinated by antiserum against A. baumannii serovar 18. Genospecies 14 (Bouvet) yielded a very weak cross-reaction with genospecies 3 serovar 20, and genospecies TU 13 reacted weakly with anti-genospecies 3 serovar 15 serum. The 'between genospecies 1 and 3' reference strain proved to be A. baumannii serovar 5 as determined with absorption tests.

Acinetobacter↗
PubMed1996

Characterization of the chromosomal cephalosporinases produced by Acinetobacter lwoffii and Acinetobacter baumannii clinical isolates.

The beta-lactamases produced by Acinetobacter lwoffii ULA-501, Acinetobacter baumannii ULA-187, and A. baumannii AC-14 strains were purified and characterized, and their kinetic interactions with several beta-lactam molecules, including substrates and inhibitors, were studied in detail. The three enzymes appeared to be cephalosporinases with different acylation efficiencies (kcat/Km ratio values), and their hydrolytic activities were inhibited by benzylpenicillin, piperacillin, and cefotaxime, which did not behave as substrates. Carbenicillin was a substrate for the beta-lactamase from A. lwoffii ULA-501, whereas it acted as a transient inactivator of the enzymes produced by the two A. baumannii strains. Clavulanic acid was unable to inactivate the three beta-lactamases, whereas sulbactam behaved as an inactivator only at a high concentration (1 mM) which is difficult to achieve during antibiotic therapy. Analysis of the interaction with 6-beta-iodopenicillanic acid also allowed us to better discriminate the three beta-lactamases analyzed in the present study, which can be included in the group 1 functional class (5).

Acinetobacter↗
PubMed1992

Ribotyping of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex.

The Acinetobacter calcoaceticus-Acinetobacter baumannii complex consists of four genotypically distinct but phenotypically very similar bacterial species or DNA groups: A. calcoaceticus (DNA group 1), A. baumannii (DNA group 2), unnamed DNA group 3 (P. J. M. Bouvet and P. A. D. Grimont, Int. J. Syst. Bacteriol. 36:228-240, 1986), and unnamed DNA group 13 (I. Tjernberg and J. Ursing, APMIS 97:595-605, 1989). Because strains in this complex cause nosocomial outbreaks, it is important to be able to identify them as completely as possible. Ribotyping could provide such identification. Therefore, ribotyping was done on 70 strains in the A. calcoaceticus-A. baumannii complex with known DNA group affiliations by use of restriction enzymes EcoRI, ClaI, and SalI. A nonradioactive digoxigenin-11-dUTP-labeled Escherichia coli rRNA-derived probe was used. With any of the three restriction enzymes, banding patterns that were specific for each DNA group were seen. All 70 strains showed banding patterns that could identify them to the correct DNA group by use of any two of the three enzymes. In addition, banding patterns that could separate strains within any one DNA group were present. The discriminatory index of P. Hunter and M. Gaston (J. Clin. Microbiol. 26:2465-2466, 1988), applied to all strains with the combined results obtained with all three enzymes, revealed a value of 0.99. For strains in each DNA group, the value varied from 0.93 to 0.98. These results indicate the high discriminatory power of the system when used for epidemiological typing.

Acinetobacter↗
PubMed1996

[Identification and typing of hospital strains of Acinetobacter calcoaceticus-Acinetobacter baumanni complex].

A collection of 95 strains of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex, isolated between 1991 and 1993 in the Prague Burn Center (BC), was studied. Ninety-one strains were isolated from 43 patients: 50 of them from burnt sites, 22 from endotracheal tube, 13 from urine, 3 from blood and 3 from venous catheter, and 4 strains were isolated from the hospital environment and the nursing staff. The strains were classified by restriction endonuclease fingerprinting of total DNA, plasmid profile analysis, ribotyping, comparison of antibiograms, biotyping and according to epidemiological data, into 31 relatedness groups each of them including 1 to 29 strains, likely to be isolates of the same strain. None of the methods used enabled to distinguish all groups. The importance of the polyphasic approach is emphasized since three multiresistant strains, isolated almost simultaneously in the BC, needed at least two methods to be distinguished (e.g. ribotyping and biotyping). Twenty-eight representative strains of different groups were identified by ribotyping: 18 of them were allocated to genomospecies 2 (A. baumannii), 5 to genomospecies 3 and 5 to genomospecies 13 sensu Tjernberg and Ursing. Only A. baumannii was found to spread among patients. Strains of two multiresistant groups persisted in the BC throughout the period studied and strains of one of these groups were responsible for an outbreak in the autumn of 1993. The methods mentioned above were used to describe 12 multiresistant strains isolated in three hospital wards in other localities. When ribotyped these strains were identified as A. baumannii. The strains of the same origin were identical in their typing profiles while the strains of different origins were easy to differentiate using any of the above methods; nevertheless, 2 of these groups were almost identical to 2 groups of multiresistant strains isolated in the BC.

Acinetobacter↗
PubMedDate not supplied

Oil-degrading Acinetobacter strain RAG-1 and strains described as 'Acinetobacter venetianus sp. nov.' belong to the same genomic species.

Acinetobacter strain RAG-1 (ATCC 31012) is an industrially important strain which has been extensively characterized with respect to its growth an hydrocarbons and its production of a high molecular mass bioemulsifier, emulsan. Although RAG-1 has been investigated in detail for specific biochemical characteristics, its taxonomic status is uncertain and it is usually referred to as A. lwoffii or A. calcoaceticus sensu lato. However, results obtained by restriction analysis of the amplified rDNA and subsequently substantiated by DNA-DNA hybridization, partial 16S rDNA nucleotide sequence comparison and biochemical characterization indicate that RAG-1 belongs to the genomic species recently described as 'A. venetianus'. Furthermore, these data confirm that 'A. venetianus' constitutes a new and distinct genomic species within the genus Acinetobacter.

Acinetobacter↗
PubMed1992

Susceptibility of isolates of Acinetobacter anitratus and Acinetobacter lwoffii to the bactericidal activity of normal human serum.

The bactericidal activity of normal human serum against the Gram-negative coccobacilli Acinetobacter anitratus and Acinetobacter lwoffii was studied; 12% and 84%, respectively, of the tested strains appeared to be sensitive. Thus, serum resistance may be an important factor contributing to the pathogenic potential of A. anitratus strains. Three types of bactericidal action were shown. In the first, the strains were killed when the alternative complement pathway was activated. In the second, some strains required both the classical and alternative pathways. In the third variant, the strains needed either the alternative or classical activation pathway.

Acinetobacter↗
PubMed1998

Effect of desiccation on the ultrastructural appearances of Acinetobacter baumannii and Acinetobacter lwoffii.

An Acinetobacter baumannii isolate survived desiccation beyond 30 days and an Acinetobacter lwoffii isolate up to 21 days. For both species, desiccation resulted in a significant increase in the proportion of round cells (A baumannii, 40% to 80%; A lwoffii, 51% to 63%) and a significant decrease in rod shaped cells (A baumannii, 58% to 13%; A lwoffii, 46% to 34%). Electronmicroscopic examination showed that there was also a corresponding significant increase in the cell wall thickness (A baumannii, up to 53%; A lwoffii, up to 26%). Desiccated A baumannii cells became more electron-dense and had significantly thicker cell walls (x1.3) than those of A lwoffii. Cell wall structures of A baumannii strains with different abilities to resist desiccation deserve further study.

Acinetobacter↗
PubMed1978

Metabolism of bile acids by strains of Acinetobacter anitratum and Acinetobacter lwoffii.

The activity of two species of bacteria: Acinetobacter anitratum and Acinetobacter lwoffii, isolated from jejunum of patients with achlorhydria and Reichel-Polya resection towards bile salts was investigated. These species were not previously tested from this view point. All strains tested hydrolyzed bile salts; conjugates of deoxycholic acid were hydrolyzed more readily than those of cholic acid. This feature may be used as a bacteriological taxonomic criterion.

Acinetobacter↗