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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↗
PubMed1996

Evaluation of the ability of a commercial system to identify Acinetobacter genomic species.

A collection of 130 Acinetobacter strains identified by DNA hybridization to 18 different genomic species was used to assess the ability of the API 20NE system (bioMérieux, France) to identify Acinetobacter genomic species and to determine its accuracy. Fifty-eight (87%) of the 67 strains of genomic species defined in the database (version 5.1) were identified to the appropriate genomic species. The Acinetobacter baumannii strains and the Acinetobacter haemolyticus strains were all identified correctly. Three of five Acinetobacter junii strains, three of eight Acinetobacter johnsonii strains, and 11 of 13 Acinetobacter lwoffii strains were also identified correctly. The 58 correctly identified strains represented 45% of the total 130 strains. Thirty-six of the 72 inappropriately identified strains were designated Acinetobacter baumannii. Thirty-one of these 36 strains belonged to genomic species 1 (Acinetobacter calcoaceticus), 3, or 13TU. Analysis of the profiles showed that the API system does not discriminate between genomic species 1, 2, 3, and 13TU. Lumping of these groups into the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in the API 20NE database would make the system considerably more accurate. Incorporation of these data into the database may improve identification of the remaining genomic species, including some that are not defined. However, the discriminative power of the tests in the API galleries is insufficient for correct identification of all Acinetobacter genomic species.

Acinetobacter↗
PubMed1972

Interspecies transformation of Acinetobacter: genetic evidence for a ubiquitous genus.

The availability of a strain of Acinetobacter competent for transformation has made it possible to demonstrate the genetic relatedness of a large variety of gram-negative, oxidase-negative, nonmotile, and aerobic coccobacilli originally classified into eleven different genera. Deoxyribonucleic acid (DNA) species from 265 such strains are capable of transforming stable auxotrophs of the competent Acinetobacter to prototrophy. The compositions of these DNA species vary from 40 to 46.8% guanine plus cytosine. Strains with widely differing phenotypic properties are also included in this collection of acinetobacters. DNA species from all oxidase-positive strains of Moraxella and from a variety of common bacteria are unable to transform the competent Acinetobacter. Although acinetobacters are usually considered to be unable to reduce nitrate to nitrite, six strains known to carry out this reduction have been shown to be authentic acinetobacters since their DNA species readily transform the competent Acinetobacter auxotrophs to prototrophy. In contrast to previous findings that acinetobacters rarely grow with glucose as a sole carbon source, the results of the present study show that 17 of the 265 strains grow readily in a glucosemineral medium, and 48 other strains can mutate spontaneously to grow in such a medium. A second competent strain of Acinetobacter, originally unable to use glucose, d-xylose, or d-ribose as carbon sources, has been transformed for ability to dissimilate these compounds using DNA species from strains that normally grow on these sugars. Although most of the 265 Acinetobacter strains studied were originally grown on complex media when isolated from human sources, only nine of these strains require growth factors in order to grow in a mineral medium containing a single carbon and energy source. A simple transformation assay has been devised for rapid examination of large numbers of strains to determine whether or not they are acinetobacters. This assay, which is suitable for routine diagnostic work, includes a procedure for preparation of crude transforming DNA from a small quantity of bacterial paste. Samples of DNA prepared from Acinetobacter cultures that had died on slants and plates were still able to effect transformation of the competent auxotrophs to prototrophy.

Aerobiosis↗
PubMed2005

Clinical impact and pathogenicity of Acinetobacter.

Members of the genus Acinetobacter have been implicated in a wide spectrum of infectious diseases. Although this organism is associated primarily with nosocomial infections, it has also been involved in cases of community-acquired infection. Before the 1970s, Acinetobacter infections were mostly post-surgical urinary tract infections in patients hospitalised in surgical units. The significant improvement in resuscitation techniques during the last 30 years has changed the types of infection caused by Acinetobacter. Since the 1980s, Acinetobacter has spread rapidly among patients in intensive care units. Today, Acinetobacter accounts for c. 9% of nosocomial infections, with most Acinetobacter infections involving the respiratory tract. Transmission via the hands of hospital staff has become the most important contributory factor in patient colonisation. Acinetobacter baumannii is the species that is involved most frequently in infections of humans, but a natural reservoir for A. baumannii outside the hospital environment has not yet been identified. Community-acquired infection and infections acquired following war or natural disasters (e.g., earthquakes) have been described. Acinetobacter causes mild-to-severe illness, but can be fatal. The severity of Acinetobacter infection depends upon the site of infection and the patient's susceptibility to infection as a result of underlying disease. The circumstances that allow Acinetobacter to assume a pathogenic role are not really well-understood. As this organism is a low-grade pathogen, the pathogenesis of Acinetobacter infections probably involves numerous factors, including virulence determinants, which have yet to be investigated.

Acinetobacter↗
PubMed1997

Phylogenetic relationship of the twenty-one DNA groups of the genus Acinetobacter as revealed by 16S ribosomal DNA sequence analysis.

The inter- and intrageneric relationships of members of the genus Acinetobacter were investigated by performing a comparative sequence analysis of PCR-amplified 16S ribosomal DNAs (rDNAs) from 21 strains representing all of the DNA groups that have been described. Phylogenetic treeing confirmed that Acinetobacter spp. form a coherent cluster within the gamma subdivision of the class Proteobacteria that includes strains with overall levels of 16S rDNA sequence similarity of more than 94%. The analysis of intrageneric relationships suggested that the majority of the strains cluster in five clearly distinguishable clusters, and this conclusion was supported by the results obtained with the different methods used for phylogenetic analysis (i.e., the maximum-likelihood, parsimony, and distance matrix methods). The first cluster contains the representatives of DNA groups 2 (Acinetobacter baumannii) and TU13, whereas the second cluster comprises representatives of DNA groups 3, "Close To TU13," and "between 1 and 3." The representatives of closely related Acinetobacter DNA groups 8 (Acinetobacter twoffii) and 9 belong to the third cluster, which includes the representative of DNA group 6 as well. The fourth cluster is formed by DNA groups BJ15, BJ16, and BJ17, and the fifth cluster comprises DNA groups 1 (Acinetobacter calcoaceticus), BJ14, 10, and 11. Within the fifth cluster the 16S rDNA sequences of DNA group 10 and 11 strains are nearly identical. The representatives of DNA groups 4 (Acinetobacter haemolyticus), 5 (Acinetobacter junii), 7 (Acinetobacter johnsonii), 12 (Acinetobacter radioresistens), TU14, and TU15 form individual branches that are not significantly affiliated with any of the five clusters identified. Apart from the clustering of the most closely related DNA groups, the general topology of the distance dendrogram revealed some discrepancy with previous DNA-DNA hybridization data, which may point to the inadequacy of comparative 16S rDNA sequence analysis for reflecting true evolutionary relationships of closely related bacterial taxa. Important, however, was the presence of unique sequence motifs in each of the 21 different DNA groups studied, which may be useful for rapid differentiation of DNA groups of the genus Acinetobacter.

Acinetobacter↗
PubMed2000

[Comparative evaluation of bacteria identification from the Acinetobacter genus using a commercially available API 20NE system, PCR and RFLP techniques].

A study was carried out for identification of 50 Acinetobacter strains isolated from various clinical materials. Using classic methods the following species were identifies: Acinetobacter sp. (68%), Acinetobacter baumanii (24%) and Acinetobacter lwofii (8%). In all strains the recA gene was found of 435-500 pz size which confirms their belonging to that genus. Amplification products were digested with restriction enzymes Mbol and HinfI (RFLP) and their detection was carried out on agarose gel by electrophoresis methods, owing to that the arrangement of gene fragment characteristic of each strain was obtained. After careful analysis restriction patterns were obtained corresponding to the following genome species: Acinetobacter baumanii (60%), Acinetobacter sp. 3 (28%) and Acinetobacter lwoffii (12%). The methods of molecular biology made possible a more precise classification of the studied strains according to species. Certain strains determined as Acinetobacter sp. by the API 20NE system were found to be Acinetobacter baumanii, Acinetobacter sp. 3 or Acinetobacter lwofii when determined by the PCR/RFLP method.

Acinetobacter↗
PubMed2005

Characterization and changing minimum inhibitory concentration (MIC) of Acinetobacter species from a tertiary care setup.

128 isolates of Acinetobacter species from admitted and outdoor patients were subjected to biotyping and resistotyping. Resistance phenotype analysis included nine antibiotics and two betalactam inhibitor combination drugs. In 100 strains of Acinetobacter spp. ciprofloxacin, amikacin, cefotaxime and cefepime minimum inhibitory concentration (MIC) was done by agar dilution using NCCLS 2002 criteria. In forty-nine isolates MIC level was determined by E-strip also. Extended spectrum beta lactamase (ESBL) production was detected by double disc synergy technique. Inducible beta lactamases (IBL's) were detected by disc approximation method. The relationship between biotypes and resistance phenotype was analyzed. Majority of isolates (93.75%) were from admitted patients. The biotyping revealed Acinetobacter calcoaceticus-Acinetobacter baumannii complex (87.2%) to be the predominant species and they were isolated from tracheal aspirates of patients with ventilator associated pneumonia. By Kirby Bauer disc diffusion antimicrobial sensitivity testing Acinetobacter spp. were most sensitive to the combination of drug cefoperazone-sulbactam (95.6%) followed by meropenem (94.6%), piperacillin-tazobactam (92.6%). On screening incidence of Imipenem Nonsensitive Acinetobacter spp. (INSA) was (5.4%). Acinetobacter spp. were typable by six resistance phenotypes and six biotypes. Most common (66.6%) resistant phenotype of A. calcoaceticus-A. baumannii complex was susceptible to cefoperazone-sulbactam and or meropenem and or piperacillin-tazobactam. ESBL production was seen in 6% and IBL (Inducible Beta Lactamase) production was seen in 7% of Acinetobacter spp. The MIC90 for ciprofloxacin was =256 microg/ml, cefotaxime 512 microg/ml, cefepime 512 microg/ml, and amikacin 32 microg/ml. Multidrug resistance was seen in more than 90% of A. calcoaceticus-A. baumannii complex and 20% of Acinetobacter lwoffii. Acinetobacter spp. has other emerging novel mechanism of resistance that requires continuous research. Simpler, reproducible and reliable methods of biotyping and their subsequent correlation with resistotyping are more cost effective than molecular methods, which are available only in reference laboratories.

Acinetobacter↗