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PubMed1995

Molecular typing of Acinetobacter baumannii-Acinetobacter calcoaceticus complex isolates from endemic and epidemic nosocomial infections.

Ribotype, biotype and resistance phenotype were used to characterize 37 Acinetobacter baumannii-A. calcoaceticus complex isolates responsible for nosocomial infections in Buenos Aires. Nineteen isolates were recovered from endemic infections at 2 hospitals and 18 represent an intensive care unit outbreak that occurred in a third hospital. By ribotyping isolates were classified into five different clones of A. baumannii biotype 2, 3 of A. baumannii biotype 9, and 3 of Acinetobacter genospecies 13. Combination of the three epidemiological markers permitted categorization of 18 outbreak isolates into four probable strains: 2 A. baumannii biotype 2, named type I, and II, and 2 A. baumannii biotype 9. Type I (15 isolates) was the most prevalent strain at one hospital and was responsible for the outbreak. In conclusion, combined analysis of biotypes, resistance phenotypes, and ribotypes was an accurate approach for epidemiologic investigation of A. baumannii. Furthermore, ribotyping discriminated Acinetobacter genospecies 13 isolates which were phenotypically difficult to type.

Acinetobacter↗

PubMed1996

Validation of use of whole-cell repetitive extragenic palindromic sequence-based PCR (REP-PCR) for typing strains belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii complex and application of the method to the investigation of a hospital outbreak.

Acinetobacter spp. are being reported with increasing frequency as causes of nosocomial infection. In order to identify reservoirs of infection as quickly as possible, a rapid typing method that can differentiate epidemic strains from environmental and nonepidemic strains is needed. In 1993, a cluster of Acinetobacter baumannii isolates from five patients in the adult intensive therapy unit of our tertiary-care teaching hospital led us to develop and optimize a rapid repetitive extragenic palindromic sequence-based PCR (REP-PCR) typing protocol for members of the Acinetobacter calcoaceticus-A. baumannii complex that uses boiled colonies and consensus primers aimed at repetitive extragenic palindromic sequences. Four of the five patient isolates gave the same REP-PCR typing pattern as isolates of A. baumannii obtained from the temperature probe of a Bennett humidifier; the fifth isolate had a unique profile. Disinfection of the probe with 70% ethanol, as recommended by the manufacturer, proved ineffective, as A. baumannii with the same REP-PCR pattern was isolated from it 10 days after cleaning, necessitating a change in our decontamination procedure. Results obtained with REP-PCR were subsequently confirmed by ribotyping. To evaluate the discriminatory power (D) of REP-PCR for typing members of the A. calcoaceticus-A. baumannii complex, compared with that of ribotyping, we have applied both methods to a collection of 85 strains that included representatives of six DNA groups within the complex. Ribotyping using EcoRI digests yielded 53 patterns (D = 0.98), whereas 68 different REP-PCR patterns were observed (D = 0.99). By computer-assisted analysis of gel images, 74 patterns were observed with REP-PCR (D = 1.0). Overall, REP-PCR typing proved to be slightly more discriminatory than ribotyping. Our results indicate that REP-PCR typing used boiled colonies is a simple, rapid, and effective means of typing members of the A. calcoaceticus-A. baumannii complex.

Acinetobacter↗

PubMed2005

Prevalence of Acinetobacter baumannii and other Acinetobacter spp. in faecal samples from non-hospitalised individuals.

In total, 226 individuals from the community were investigated for faecal carriage of Acinetobacter spp. by broth enrichment culture, followed by growth on blood agar and/or Leeds Acinetobacter Medium (LAM). Acinetobacter baumannii was isolated on both LAM and blood agar from one of 100 specimens in the UK and one of 126 specimens in The Netherlands. The predominant species were Acinetobactor johnsonii and genomic sp. 11, which were cultured from 22 and five specimens, respectively. A. baumannii did not seem to be widespread in the faecal flora of individuals in the community.

Acinetobacter Infections↗

PubMed2001

Antibody responses to Acinetobacter spp. and Pseudomonas aeruginosa in multiple sclerosis: prospects for diagnosis using the myelin-acinetobacter-neurofilament antibody index.

Antibody responses to Acinetobacter (five strains), Pseudomonas aeruginosa, Escherichia coli, myelin basic protein (MBP), and neurofilaments were measured in sera from 26 multiple sclerosis (MS) patients, 20 patients with cerebrovascular accidents (CVA), 10 patients with viral encephalitis, and 25 healthy blood donors. In MS patients, elevated levels of antibodies against all strains of Acinetobacter tested were present, as well as antibodies against P. aeruginosa, MBP, and neurofilaments, but not antibodies to E. coli, compared to the CVA group and controls. The myelin-Acinetobacter-neurofilament antibody index appears to distinguish MS patients from patients with CVAs or healthy controls. The relevance of such antibodies to the neuropathology of MS requires further evaluation.

Acinetobacter↗

PubMed2002

Community-acquired bacteremic Acinetobacter pneumonia in tropical Australia is caused by diverse strains of Acinetobacter baumannii, with carriage in the throat in at-risk groups.

Acinetobacter isolates from eight subjects with community-acquired Acinetobacter pneumonia (CAAP), a major cause of fatal community-acquired pneumonia in tropical Australia, were phenotypically and genotypically confirmed by pulsed-field gel electrophoresis analysis to be broadly diverse Acinetobacter baumannii strains. Wet-season throat carriage of A. baumannii was found in 10% of community residents with excess levels of alcohol consumption, the major at-risk group for CAAP.

Acinetobacter↗

PubMed1996

[Bactericide activity of sulbactam before bacteria belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii complex].

BACKGROUND: To evaluate the bactericidal activity of colistin, imipenem and sulbactam against 24 Acinetobacter calcoaceticus-Acinetobacter baumannii complex isolations. METHODS: Bactericidal activity was estimated by using killing curves method. The concentrations employed were: colistin 4 mg/l, imipenem 8 mg/l and sulbactam 8 and 32 mg/l. RESULTS: Colistin was bactericidal in 24 isolations after 6 hours of incubation. When we used 8 mg/l of imipenem we detected bactericidal activity at the susceptible strains (MIC < or = 4 mg/l). We found bactericidal effect in 15 of 18 strains susceptible to sulbactam when we used 8 mg/l in killing curves after 24 hours of incubation. Using 32 mg/l we detected the same effect in 18 strains with MIC < or = 8 mg/l. CONCLUSIONS: Considering the high incidence of resistance in Acinetobacter spp. to several antibiotics including imipenem, we consider that sulbactam could be an excellent therapeutic alternative because it presents bactericidal activity in susceptible strains.

Acinetobacter↗

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↗

PubMed2006

Naturally transformable Acinetobacter sp. strain ADP1 belongs to the newly described species Acinetobacter baylyi.

Genotypic and phenotypic analyses were carried out to clarify the taxonomic position of the naturally transformable Acinetobacter sp. strain ADP1. Transfer tDNA-PCR fingerprinting, 16S rRNA gene sequence analysis, and selective restriction fragment amplification (amplified fragment length polymorphism analysis) indicate that strain ADP1 and a second transformable strain, designated 93A2, are members of the newly described species Acinetobacter baylyi. Transformation assays demonstrate that the A. baylyi type strain B2(T) and two other originally identified members of the species (C5 and A7) also have the ability to undergo natural transformation at high frequencies, confirming that these five strains belong to a separate species of the genus Acinetobacter, characterized by the high transformability of its strains that have been cultured thus far.

Acinetobacter↗

PubMed2003

The concentrations of hexadecane and inorganic nutrients modulate the production of extracellular membrane-bound vesicles, soluble protein, and bioemulsifier by Acinetobacter venetianus RAG-1 and Acinetobacter sp. strain HO1-N.

In the present study, we addressed the possibility that the production of both bioemulsifiers and membrane-bound vesicles may be a common feature of the growth of Acinetobacter spp. on alkanes, and we determined the extent to which the release of extracellular products by these organisms is regulated by the concentrations of the alkane substrate and inorganic nutrients. To accomplish this objective, we grew Acinetobacter venetianus RAG-1 and Acinetobacter sp. strain HO1-N with different concentrations of nutrients and assayed for extracellular products. The results indicated that the release of vesicles, soluble protein, and bioemulsifier was promoted in various degrees by higher concentrations of hexadecane and inorganic nutrients, while the specific activities of the bioemulsifiers were enhanced with lower nutrient concentrations. Based on our findings, we propose that under conditions of nutrient excess, these strains produce membrane-bound vesicles to function in "luxury uptake" of the alkane substrate for delivery and storage in the form of inclusions. Under the same conditions, soluble bioemulsifier and protein may perform auxiliary roles in cell desorption and (or) alkane uptake. With low concentrations of nutrients, the decreased production of vesicles, protein, and bioemulsifier and the increased activity of the emulsifier may represent a mechanism for reducing biosynthetic demands and conserving cellular material.

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↗