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PubMed2006

3-Methylglutaconyl-CoA hydratase from Acinetobacter sp.

Acinetobacter strain IVS-B aerobically grows on isovalerate as sole carbon and energy source. Isovalerate is metabolised via isovaleryl-CoA, an intermediate of the oxidative (S)-leucine degradation pathway. A 3-methylglutaconyl-CoA hydratase (EC 4.2.1.18) was purified 65-fold to apparent homogeneity from cell-free extracts of isovalerate-grown cells of Acinetobacter strain IVS-B. The enzyme was found to be a homotetramer (115.2 kDa) composed of four identical subunits of 28.8 kDa not containing any cofactors. The enzyme was shown to catalyse the hydration of (E)-glutaconyl-CoA (k (cat)=18 s(-1), K (m)=40 microM) and the dehydration of (S)-3-hydroxyglutaryl-CoA (k (cat)=13 s(-1), K (m)=52 microM), albeit with somewhat lower catalytic efficiencies as compared to the 3-methyl derivatives, 3-methylglutaconyl-CoA (k (cat)=138 s(-1), K (m)=14 microM) and (S)-3-hydroxy-3-methylglutaryl-CoA (k (cat)=60 s(-1), K (m)=36 microM). Thus, the mechanistically simple syn-addition of water to the (E)-isomer of 3-methylglutaconyl-CoA of the leucine degradative pathway leading to the common intermediate (S)-3-hydroxy-3-methylglutaryl-CoA was assigned as the major physiological role to this enzyme. The amino acid sequence of 3-methylglutaconyl-CoA hydratase from Acinetobacter sp. was found to be related to over 100 prokaryotic enoyl-CoA hydratases (up to 50% identity), possibly all being 3-methylglutaconyl-CoA hydratases.

Acinetobacter↗

PubMed2005

A unique polypeptide from the C-terminus of the exocellular esterase of Acinetobacter venetianus RAG-1 modulates the emulsifying activity of the polymeric bioemulsifier apoemulsan.

An exocellular esterase from the oil-degrading Acinetobacter venetianus RAG-1 was previously shown to enhance the emulsification and emulsion stabilization properties of the amphipathic, aminopolysaccharide bioemulsifier, emulsan [Bach H, Berdichevsky Y, Gutnick D (2003) An exocellular protein from the oil-degrading microbe Acinetobacter venetianus RAG-1 enhances the emulsifying activity of the polymeric bioemulsifier emulsan. Appl Environ Microbiol 69:2608-15]. This enhancement was specific for the RAG-1 esterase and was independent of catalytic activity. In this report, fragments from both the N'- and C'-termini were cloned as fusions to the C-terminus of the maltose-binding protein (MBP) and were tested for enhancement activity in the presence of the deproteinated form of emulsan, apoemulsan. The activity could be localized to the C-terminal third of the protein which exhibited the same activity as the intact enzyme. MBP itself was completely inactive and could be cleaved from the fusion without affecting the subsequent emulsification. However, the enhancement completely depended on the presence of a unique C-terminal 20 amino acid peptide not found in any other protein in the databases. In addition, progressive removal of amino acids from the N-terminus of the active MBP polypeptide resulted in a concomitant loss of activity, indicating that enhancement is also proportional to the size of the peptide fragment. The middle third and the C-terminal third of the enzyme each contained a copy of the conserved Cardin-Weintraub consensus sequence for protein binding to heparin. These sequences were not detected in homologous esterases from a closely related strain, Acinetobacter calcoaceticus BD413.

Acinetobacter↗

PubMed1989

Epidemic iatrogenic Acinetobacter spp. meningitis following administration of intrathecal methotrexate.

We report the first outbreak of Acinetobacter species meningitis in a group of children with acute leukaemia following the administration of intrathecal chemotherapy. Eight of twenty patients receiving methotrexate injections on a single day developed signs and symptoms of meningitis within 18 h of treatment, and cases were clustered by time of administration. A cohort study comparing case and non-case patients did not identify any specific host factor associated with meningitis. Acinetobacter calcoaceticus var anitratus was isolated from the cerebrospinal fluid (CSF) of five patients; three patients died. Our investigation determined that the methotrexate was extrinsically contaminated by reused needles, used for reconstitution and administration, which had been inadequately sterilized. Acinetobacter calcoaceticus var anitratus was isolated from an autoclaved needle and a vial of methotrexate used for chemotherapy; these and the clinical isolates had similar antibiograms. After introduction of single-use disposable needles no subsequent cases occurred.

Acinetobacter Infections↗

PubMed1990

Epidemiological surveillance of Acinetobacter species.

Two hundred and sixty Acinetobacter isolates were recovered from 237 patients over a 2-year period; 156 isolates from 135 spinal cord injuries unit (SCIU) patients and 104 isolates from 102 patients in all the other hospital units. In SCIU patients, 133 isolates were recovered from the urine, 21 from wounds and aspirates, one from sputum and one from blood culture. In non-SCIU patients, 12 isolates were recovered from urine, 43 from wounds and aspirates, 48 from sputum and one from blood culture. Sixty-nine percent of isolates from SCIU patients showed resistance to gentamicin compared to 3% from non-SCIU patients. Gentamicin-resistant Acinetobacter anitratus was recovered from many environmental sites in the SCIU wards and from the hands of seven of 94 SCIU staff members tested. Serial rectal swabs were obtained from 79 newly-diagnosed SCIU patients. Ninety-two percent of those patients followed for up to 5 months acquired gentamicin-resistant Acinetobacter anitratus in their intestinal tract. API 2ONE profiles and antibiograms suggested that two distinct gentamicin-resistant strains of A. anitratus had become endemic in the SCIU and that nosocomial transmission was a frequent occurrence.

Acinetobacter Infections↗

PubMed1991

Hospital infection with Acinetobacter spp.: an increasing problem.

During the last few years, among nosocomial pathogens, Acinetobacter spp. have given rise to an increasing number of nosocomial infections. Acinetobacter strains are widely distributed in nature; in hospitals, the human skin is the likely source for most outbreaks of hospital infections. The organism has been frequently found in the inanimate environment, especially in moist situations and it has been isolated from various types of opportunistic infections (septicaemia, endocarditis, meningitis, pneumonia, skin and wound sepsis and urinary tract infection). For epidemiological studies, various typing methods such as biotyping, bacteriocin typing and serology have been developed. More recently electrophoretic patterns of cell-envelope proteins and plasmid analysis have proved useful in differentiating outbreak strains. Antibiogram typing may be useful but the antibiotic resistance of Acinetobacter spp. has changed rapidly within the last few years and thus antibiotyping must be complemented by other typing systems. New methods such as electrophoretic analysis of isoenzymes, definition of plasmidotype profiles or restriction endonuclease digestion of chromosomal DNA are under investigation.

Acinetobacter Infections↗

PubMedDate not supplied

Delineation of new proteolytic genomic species in the genus Acinetobacter.

Twenty-seven proteolytic Acinetobacter strains differing phenotypically from the 12 previously described Acinetobacter species were studied by DNA/DNA hybridization using the S1 nuclease method to assess their relatedness. Five DNA groups (genomic species 13 to 17) containing 20 strains were delineated. Seven strains remained ungrouped. Within species, the level of DNA relatedness to the reference strains ranged from 64 to 99%, with delta Tm values below 3.5 degrees C. DNA group 13 was 31 to 42% related to group 14. DNA group 15 was 59 to 69% related to group 16, with delta Tm values between 4.5 and 6 degrees C. DNA group 17 was 51 to 61% related to DNA groups 15 and 16 with delta Tm values between 5.5 and 7.5 degrees C. The seven ungrouped strains were 28 to 60% related to the five newly delineated genomic species with delta Tm between 6.5 and 13.5 degrees C. Reference strains of the five genomic species were 5 to 22% related to the type or reference strains of the 12 Acinetobacter genomic species previously described. Biochemically, DNA groups 13 to 17 and ungrouped strains could not be separated unambiguously and therefore are not named.

Acinetobacter↗

PubMed2005

PER-1 is still widespread in Turkish hospitals among Pseudomonas aeruginosa and Acinetobacter spp.

PER-1 type beta-lactamases were screened among ceftazidime-resistant clinical isolates of Acinetobacter spp. and Pseudomonas aeruginosa. A total of 176 non-repetitive isolates (84 Acinetobacter spp. and 92 P. aeruginosa) were collected during a three month surveillance period. Isolates were obtained from seven intensive care units of seven university hospitals. All strains were screened for bla(PER-1) alleles by PCR. Of the strains, 31% and 55.4% of Acinetobacter spp. and P. aeruginosa were positive for bla(PER-1) type genes, respectively.

Acinetobacter↗

PubMed1986

Molecular cloning of the structural gene for Acinetobacter citrate synthase.

The structural gene for citrate synthase of Acinetobacter anitratum has been cloned in Escherichia coli in a form which expresses the enzyme. A library of EcoRI fragments of Acinetobacter genomic DNA was prepared in the vector lambda gt10, and clones were screened by hybridization with an E. coli citrate synthase clone under conditions of reduced stringency. A 6.5 kbp clone was obtained which was subcloned into pBR322, and shown to direct the formation of Acinetobacter citrate synthase in E. coli hosts. The promoter was located within a BglII fragment, and from this information the orientation of the gene was deduced.

Acinetobacter↗

PubMed2001

[Postsurgical meningitis caused by Acinetobacter baumannii: study of 22 cases and review of the literature].

BACKGROUND: Postsurgical Acinetobacter baumannii meningitis is associated with relevant morbidity and mortality. It has been related to neurosurgery, intraventricular catheters (IC) or CSF fistula. Thus, features, epidemiology and clinical course of this infection were studied. METHODS: Retrospective analysis of 22 episodes of nosocomial postsurgical Acinetobacter baumannii meningitis. Twenty episodes occurred in males. The mean age of patients was 46 years (range: 16-83 years). RESULTS: All patients were admitted to the ICU. In 50% of patients a history of intraventricular hemorrhage was recorded, 36% had had a skull fracture and the remaining patients had a brain tumor. In 18 cases the portal of entry was considered to be IC, in two an epidural catheter, and in two a CSF fistula. Patients showed a clinical picture indistinguishable from other types of meningitis, fever being the most common symptom (100%). CSF findings were consistent with bacterial meningitis. In one case the microorganism was recovered from blood. Fifteen patients recovered, three died as a direct result of the infection, and the remaining patients relapsed. Non recovery of patients was significantly associated with non removal of catheter (p < 0.05). CONCLUSIONS: Postsurgical Acinetobacter baumannii meningitis occurs frequently in patients previously colonized with this microorganism in other sites and is enhanced by the presence of an IC. Catheter removal is essential for recovery of patients.

Acinetobacter Infections↗

PubMed2002

Kinetics of phenol and chlorophenol utilization by Acinetobacter species.

Although microbial transformations via cometabolism have been widely observed, the few available kinetic models of cometabolism have not adequately addressed the case of inhibition from both the growth and nongrowth substrates. The present study investigated the degradation kinetics of self-inhibitory growth (phenol) and nongrowth (4-chlorophenol, 4-CP) substrates, present individually and in combination. Specifically, batch experiments were performed using an Acinetobacter isolate growing on phenol alone and with 4-CP present. In addition, batch experiments were also performed to evaluate the transformation of 4-CP by resting, phenol-induced Acinetobacter cultures. The Haldane kinetic model adequately predicted the biodegradation of phenol alone, although a slight discrepancy was noted in cases of higher initial phenol concentrations. Similarly, a Haldane model for substrate utilization was also able to describe the trends in 4-CP transformation by the resting cell cultures. The 4-CP transformation by the Acinetobacter species growing on phenol was modeled using a competitive kinetic model of cometabolism, which included growth and nongrowth substrate inhibition and cross-inhibition terms. Excellent agreement was obtained between the model predictions using experimentally estimated parameter values and the experimental data for the synchronous disappearance of phenol and 4-CP.

Acinetobacter↗

PubMed2003

Relationship between nosocomial Acinetobacter species occurring in two geographical areas (Greece and the UK).

Fifty-two isolates of Acinetobacter spp. obtained from three Greek and one UK hospital, were studied using partial 16 S ribosomal DNA sequence analysis, repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) mediated fingerprinting and DNA macro-restriction analysis. The aim was twofold: first, to discern the major differences in the population of Acinetobacter spp. between the two countries. Second, to compare a simple PCR-based typing scheme with pulsed-field gel electrophoresis (PFGE). The multi-resistant Greek isolates were within DNA groups 2 and TU13, and clustered into three types both by REP-PCR and PFGE. By contrast, the more susceptible Oxford isolates were heterogeneous on 16 S RNA sequence analysis and distinguishable on typing. The need for studies that elucidate the phylogeny of Acinetobacter spp. inside and outside hospitals are important, as this will help clarify the relationship between organisms that are increasingly recognized as causes of severe infections.

Acinetobacter Infections↗

PubMed2003

Intergeneric coaggregations among Oligotropha carboxidovorans and Acinetobacter species present in activated sludge.

The coaggregation traits of two pairs of sewage sludge bacteria were tested and characterized. Oligotropha carboxidovorans S23 coaggregated with two strains of the genus Acinetobacter viz. Acinetobacter junii S33 (56%) and Acinetobacter johnsonii S35 (99%). Coaggregates of O. carboxidovorans S23 and A. junii S33 were small (20-40 microm), weak and susceptible to EDTA and a commercial protease (Actinase E). Actinase/periodate pretreatment of the partners prior to coaggregation revealed that interaction in this case was mediated by protein surface components. Coaggregates of O. carboxidovorans S23 and A. johnsonii S35 were large (above 100 microm), strong and not deflocculated by EDTA or Actinase E. Only periodate pretreatment of A. johnsonii S35 prevented this coaggregation indicating a role for a carbohydrate-containing moiety without the involvement of protein components. The potential mechanisms and strength of bacterial coaggregations seem to be pair dependent.

Acinetobacter↗

PubMed1998

Evaluation of amplified ribosomal DNA restriction analysis for identification of Acinetobacter genomic species.

Further to a previous study, the usefulness of amplified ribosomal DNA restriction analysis (ARDRA) for identification of Acinetobacter genomic species (DNA groups) was tested. A set of 202 Acinetobacter strains of 18 described genomic species and 17 unclassified strains were used. Restriction patterns obtained with a standard panel of restriction enzymes CfoI, AluI, MboI, RsaI and MspI allowed for separation of 11 DNA groups. With the additional use of restriction enzymes BfaI and BsmAI, five other (genomic) species could be differentiated, leaving only A. haemolyticus and DNA group 13BJ/14TU unseparated. With the standard panel of enzymes, ten new ARDRA profiles were noted in 14 unclassified strains. Two other unclassified strains had a profile in common with DNA group 15BJ, but were differentiated from this DNA group by restriction with bfaI. One remaining unclassified strain could not be differentiated from DNA group 17 by the standard panel of enzymes or by the enzymes BfaI and BsmAI. Results demonstrate the utility of ARDRA for identification of most genomic species of Acinetobacter. Furthermore, new ARDRA profiles that were shared by several unclassified strains may indicate so far undescribed genomic species in the genus.

Acinetobacter↗

PubMed2001

Random amplified polymorphic DNA analysis of Acinetobacter species isolated from worn contact lenses.

The purpose of this study was to explore the genotypes of Acinetobacter species and to compare the genotypes and phenotypes of the Acinetobacter isolated from contact lens wearers. Nineteen strains were used in the study, 13 were isolated from patients experiencing an adverse response event, and six strains were isolated from asymptomatic contact lens wearers. Random amplified polymorphic DNA and phenotypic analyses were carried out using commercially available kits. Random amplified polymorphic DNA analysis showed a higher discrimination power compared with the phenotypic analysis. The test strains were loosely clustered into six genotypic groups with no definite relation to any clinical events. These results indicate that many genotypes of Acinetobacter can cause adverse responses, and the initial source of the microorganisms rather than their clinical sequelae may determine classification.

Acinetobacter↗

PubMed2000

Problem pathogens (Pseudomonas aeruginosa and Acinetobacter).

A number of factors have been suspected of or identified as increasing the risk for pneumonia or colonization of the lower respiratory tract by Pseudomonas and/or Acinetobacter spp. in the intensive care unit (ICU), including advanced age, chronic lung disease, immunosuppression, surgery, use of antimicrobial agents, presence of such invasive devices as endotracheal and gastric tubes, and type of respiratory equipment. However, there is little doubt that of all these factors, extended ICU care because of severe underlying disease, prolonged respiratory therapy with mechanical ventilation, and prior antimicrobial therapy are the most important. Because the only factor amenable to prevention in this setting is antimicrobial therapy, avoiding unnecessary antibiotics should be a high priority in the management of such patients. Crude mortality rates of 30% to 75% have been reported for nosocomial pneumonia caused by Pseudomonas and/or Acinetobacter spp., with the highest rates reported in ventilator-dependent patients. It is therefore clear that the prognosis associated with this type of infection is considerably worse than that associated with infection caused by other gram-negative or gram-positive bacteria. Because bactericidal synergy against Pseudomonas and Acinetobacter spp. has been shown when carbenicillin and an aminoglycoside are combined, the use of an effective beta-lactam (piperacillin, ticarcillin, ceftazidime, or imipenem) and aminoglycoside combination remains the preferred therapeutic approach when possible. Future research efforts should also aim to improve our ability to diagnose and exclude infection in the ICU setting to avoid administering unnecessary antibiotics to patients without true pulmonary infection.

Acinetobacter Infections↗

PubMed2004

Variation of 16S-23S rRNA intergenic spacer regions (ISRs) in Acinetobacter baylyi (strain B2) isolated from activated sludge.

To determine the variability of the 16S-23S rRNA intergenic spacer region (ISR) of the newly described Acinetobacter baylyi, 88 clones containing ISR amplicons were screened and 14 chosen for further analysis. Two different sized 16S-23S rRNA ISRs were distinguished comprising five variable and four conserved nucleotide blocks. The major regions of heterogeneity between the different sized ISRs were due to blocks of substitutions with unique secondary structures interspersed with nucleotide substitutions, rather than differences caused by presence or absence of tRNA genes, which is often the case. Recombination events causing shuffling of nucleotide blocks are considered the most likely explanation for the mosaic structure observed between the different copies of the ISR. Single base differences present in the long ISR (LISR) were then exploited in attempts to detect possible heterogeneity between rrn copies in Acinetobacter baylyi but variability was not detected by RFLP analysis of LISR-specific PCR products. These primers were shown to be highly specific for 3 Acinetobacter baylyi strains based on LISR sequence homogeneity.

Acinetobacter↗

PubMed2006

Structural investigations on novel porin, OmpAb from Acinetobacter baumannii.

Acinetobacter baumannii is an opportunistic pathogen and known to cause nosocomial infections especially in ICUs of hospitals. We have previously reported that the novel outer membrane protein, OmpAb from Acinetobacter baumannii is a transmembrane porin and plays an important role in transport of small molecules, like antibiotics across the membrane. In the present study we report the N-terminal sequence, Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) analysis of OmpAb and structural investigations using UV-Vis absorption, circular dichroism (CD), and fluorescence on OmpAb. SDS-PAGE results suggest that OmpAb is actually a "heat modifiable monomer" and is of 37 kDa at room temperature. Secondary structure of OmpAb is being done for the first time that showed predominantly beta-sheet structure (68%), a feature characteristic of porins. Using N-Bromosuccinimide (NBS) as oxidizing agent, the total number of tryptophans in OmpAb is estimated to be four. The present results indicate that out of the four, two tryptophans seem to be located in the integral part of the membrane, perhaps periplasmic/membrane-bound while the other two tryptophans are exposed to the solvent. We followed the fluorescence emission using conventional 280 nm and selective 305 nm excitation (established by us earlier) to explore the environment of four tryptophans in OmpAb. Emission results using selective excitation of 305 nm revealed local conformational changes of those "tryptophans which are on the surface". On urea denaturation and pH dependent denaturation there is a loss of beta-sheet structure by more than 70%, this is concomitant with the increase in fluorescence intensity and red shift in lambda(max, em). As reflected by CD spectral data, we also found that OmpAb is fairly stable like other porins up to 70 degrees C. As there are no reports on the structural aspects of any outer membrane proteins of Acinetobacter baumannii, results presented here on this novel major porin, OmpAb, will help in understanding the structure-function relationship.

Acinetobacter baumannii↗

PubMed1999

Acinetobacter junii causes life-threatening sepsis in preterm infants.

Acinetobacter junii caused sepsis in six preterm infants in our neonatal unit within 48 h. Each infant with clinical signs of systemic infection and activation of the acute phase response had two positive blood cultures with Acinetobacter junii. The sudden onset, the short duration of the outbreak and the fact that none of the infants were colonized by A. junii suggested a common source of A. junii administered directly into the blood. The only feature shared by all six affected newborns was an intravenous fat emulsion (Intralipid 10%), which was shown to be an excellent growth medium for A. junii. Sepsis did not occur in four infants with 20% fat emulsion or amino acids only. Vaminolact did not support growth of the outbreak strain. The immediate source of the outbreak could not be identified: samples of the actual feeds given were not available for investigation, but A. junii was not isolated from parenteral solutions with identical batch numbers used in the septic infants. We conclude that Acinetobacter junii can cause a life-threatening infection in preterm neonates. Contaminated intravenous fat emulsion is implicated as a possible source of the infection. As a part of rigid infection control, intravenous feedings should be prepared under aseptic conditions.

Acinetobacter Infections↗