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PubMed1983

Pseudomonas aeruginosa and Acinetobacter calcoaceticus: in vitro susceptibility of 150 clinical isolates to five beta-lactam antibiotics and tobramycin.

The in vitro activities of azlocillin, carbenicillin, ceftriaxone, piperacillin, N-formimidoyl thienamycin (N-f thienamycin) and tobramycin have been compared against clinical isolates of Pseudomonas aeruginosa (n = 100) and Acinetobacter calcoaceticus (n = 50). An agar dilution method was employed for measurement of minimal inhibitory concentration (MIC). Tobramycin was the most active drug against P. aeruginosa (MIC less than or equal to 2 mg/l). Of the beta-lactam antibiotics, N-f thienamycin and tobramycin were highly active against A. calcoaceticus (MIC less than or equal to 2 mg/l), although one isolate was resistant to tobramycin (MIC greater than 16 mg/l). The other drugs were only moderately active against A. calcoaceticus.

Acinetobacter↗
PubMed1989

In vitro activity of fleroxacin and 6 other antimicrobials against Acinetobacter anitratus.

The in vitro activity of the 4-quinolone compound fleroxacin (Ro-23-6240) was compared with that of enoxacin, ofloxacin, cefepime (BMY-28142), ceftazidime, ceftriaxone, and tobramycin against a total of 30 recent clinical isolates of Acinetobacter calcoaceticus subsp. anitratum. Susceptibility testing (MIC50/MIC90) was performed by a microtiter broth dilution method and the combination effect of ceftriaxone plus tobramycin was studied by checkerboard titration in microtiter trays. Fleroxacin inhibited most A. calcoaceticus subsp. anitratum at 1 microgram/ml and was as active as enoxacin or tobramycin but slightly less active than ofloxacin (MIC50 = 0.25 microgram/ml; MIC90 = 2.5 microgram/ml) or cefepime (BMY-28142: MIC50 = 0.25 microgram/ml; MIC90 = 1 microgram/ml). Ceftazidime and ceftriaxone were inactive (MIC90 = 8 micrograms/ml and 32 micrograms/ml, respectively). The combination of ceftriaxone plus tobramycin was synergistic in 16.7%, additive in 60%, and indifferent in 23.3%.

Acinetobacter↗
PubMed1991

Imipenem resistance in Acinetobacter baumanii is due to altered penicillin-binding proteins.

The comparison of a clinical Acinetobacter baumanii isolate (strain No. 4852/88) and its selected imipenem-resistant (IMR) clone exhibited a complex reorganization of the penicillin-binding proteins (PBPs) with diminished labelling of all PBPs except the 24-kD PBP which showed an increased binding of 14C-penicillin. This protein could not be saturated by preincubation of membranes with imipenem at 8-fold the MIC of imipenem, thus indicating PBP alterations responsible for imipenem resistance. In A. baumanii 4852/88 seven PBPs with the apparent molecular weights of 94, 84, 65, 61, 48, 40 and 24 kD could be detected. beta-Lactamase production was barely detectable in any case and could not be enhanced in the presence of various beta-lactams as the inducer. The outer membrane proteins were found identical in both the wild-type strain and the Im clone. So far, imipenem-resistant A. baumanii isolates have been isolated twice in our diagnostic laboratory; however, no implications on the future relevance of the above findings can be made.

Acinetobacter↗
PubMed1988

Acinetobacter calcoaceticus foot infection secondary to high-pressure injection injury: a case report.

Injection injuries are surgical emergencies occurring most often in the hand and frequently associated with widespread tissue necrosis and infection. This report presents a case of high-pressure injection injury of the foot associated with extensor hallucis longus laceration and infection with Acinetobacter calcoaceticus variant anitratus. This injury occurred with a high-pressure "water-blaster" tool used to remove paint from pavement. Similar injuries in the foot have not been reported. A. calcoaceticus is a widely distributed normal flora of low virulence, often waterborne, which is rarely found in orthopaedic infections in young healthy patients. Clinical features of high-pressure injection injuries, principles of treatment, and the characteristics of A. calcoaceticus are reviewed.

Accidents, Occupational↗
PubMed1996

In vitro bactericidal effect of a beta-lactam+aminoglycoside combination against multiresistant Pseudomonas aeruginosa and Acinetobacter baumannii.

Pseudomonas aeruginosa and Acinetobacter baumannii are frequently isolated in hospital outbreaks of nosocomial infections. In our hospital, among 1018 strains isolated one year in an intensive care unit, 84 strains (8.3%) of P. aeruginosa and 155 strains (15.2%) of A. baumannii were considered responsible for infections. The major problem related to these bacteria is their multiresistant characteristic which confers great difficulty in treating infections. We carried out a 24 h time-kill study to assess the bactericidal effect of three beta-lactams [imipenem (IPM), ticarcillin+clavulanic acid (TCC), piperacillin+tazobactam (PTB)] in combination with each other and with sulbactam (SUL) and amikacin (AKN) against 8 P. aeruginosa strains and 8 A. baumannii strains. The initial inoculum was 10(6) cfu/ml. Antibiotics were tested at clinically achievable concentrations: TCC (112 mg/l), PTB (100 mg/l), IPM (25 mg/l) and AKN (15 mg/l). The results showed: IMP + TCC + AKN = PTB + SUL + AKN = PTB + TCC + AKN > > IMP + SUL + AKN against P. aeruginosa; and PTB + SUL + AKN = PTB + TCC + AKN > IMP + SUL + AKN or IMP + TCC + AKN against A. baumannii. When infection due to these multiresistant strains was suspected, PTB + AKN combined with either TCC or SUL was bactericidal against both strains. These combinations appeared to be an alternative therapy in the treatment of undocumented nosocomial infections in intensive care units. These in vitro results are being evaluated in patients and seem to give good results for the moment.

Acinetobacter↗
PubMed1996

In vitro activity of ampicillin-sulbactam against clinical multiresistant Acinetobacter baumannii isolates.

We evaluated the in vitro activity of ampicillin-sulbactam in comparison with that of broad-spectrum antimicrobial agents against Acinetobacter baumannii isolates. Two hundred and twelve clinical isolates collected between January 1993 and March 1995 from two tertiary hospitals located in São Paulo, Brazil were tested for susceptibility by the disk diffusion method against several broad-spectrum antimicrobial agents, including imipenem, ciprofloxacin, ceftazidime, aztreonam, amikacin, and polymyxin B. All strains were susceptible to polymyxin B. The second most active compound was the combination ampicillin-sulbactam (88% susceptibility). Only 79% of the isolates were susceptible to imipenem. Ciprofloxacin was active against 60 (28%) and amikacin against 34 (16%) isolates. Ceftazidime was the most active cephalosporin; however, only 9% of the isolates were susceptible to this compound. Both aztreonam and ampicillin alone showed very poor activity against this species (1% susceptibility). The prevalence of severe infections due to A. baumannii is increasing very rapidly in the tertiary hospitals of São Paulo and there are very few options for the treatment of these infections. Polymyxin B is invariably in vitro active against this species; however, this compound can cause severe side effects and is not commercially available for intravenous use in Brazil and in several other countries. Our results indicated that the combination ampicillin-sulbactam may be an alternative drug for the treatment of infections due to multiresistant A. baumannii; however, further studies are necessary to evaluate the clinical role of this compound for the treatment of severe infections.

Acinetobacter↗
PubMed2005

In vitro activity of beta-lactam antimicrobial agents in combination with aztreonam tested against metallo-beta-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii.

We evaluate the antimicrobial interactions between aztreonam and selected beta-lactams when tested against metallo-beta-lactamase (MbetaL)-producing clinical strains. Ten Pseudomonsa aeruginosa strains, including nine MbetaL-producers (IMP-1, -2, -13, -16, VIM-1, -2, -7, SPM-1 and GIM-1) and five Acinetobacter baumannii strains, including three MbetaL-producers (IMP-1 and -2) were tested using time kill/bactericidal activity methods. Aztreonam at 4, 8 and 16 mg/L was combined with four other beta-lactam antimicrobials (cefepime, ceftazidime, meropenem and piperacillin/tazobactam or ampicillin/sulbactam), each tested at the recognized susceptible breakpoint concentration. Enhanced activity (synergism or additive effect) was observed with four P. aeruginosa strains (IMP-16, VIM-2, SPM-1 and GIM-1 containing strains) and four A. baumannii strains, while antagonism was observed with two P. aeruginosa (IMP-16 and SPM-1-producing strains) and one A. baumannii (non-MbetaL) strain. All other strains showed indifferent interaction (variation of +/- 1 log10 CFU/ml) with any combination evaluated.

Acinetobacter baumannii↗
PubMed2001

Monoclonal antibodies against the iron regulated outer membrane Proteins of Acinetobacter baumannii are bactericidal.

BACKGROUND: Iron is an important nutrient required by all forms of life.In the case of human hosts,the free iron availability is 10(-18) M,which is far less than what is needed for the survival of the invading bacterial pathogen. To survive in such conditions, bacteria express new proteins in their outer membrane and also secrete iron chelators called siderophores. RESULTS/ DISCUSSION: Acinetobacter baumannii ATCC 19606, a nosocomial pathogen which grows under iron restricted conditions, expresses four new outer membrane proteins,with molecular weight ranging from 77 kDa to 88 kDa, that are called Iron Regulated Outer Membrane Proteins (IROMPs). We studied the functional and immunological properties of IROMPs expressed by A.baumanii ATCC 19606. The bands corresponding to IROMPs were eluted from SDS-PAGE and were used to immunize BALB/c mice for the production of monoclonal antibodies. Hybridomas secreting specific antibodies against these IROMPs were selected after screening by ELISA and their reactivity was confirmed by Western Blot. The antibodies then generated belonged to IgM isotype and showed bactericidical and opsonising activities against A.baumanii in vitro. These antibodies also blocked siderophore mediated iron uptake via IROMPs in bacteria. CONCLUSION: This proves that iron uptake via IROMPs,which is mediated through siderophores,may have an important role in the survival of A.baumanii inside the host,and helps establishing the infection.

Acinetobacter↗
PubMed2006

In-vitro activity of polymyxin B in combination with imipenem, rifampicin and azithromycin versus multidrug resistant strains of Acinetobacter baumannii producing OXA-23 carbapenemases.

BACKGROUND: Acinetobacter baumannii has emerged as a major nosocomial pathogen worldwide. Many of the circulating strains exhibit multi-drug resistance remaining consistently susceptible only to polymyxins. In-vitro studies have reported that polymyxins combined with carbapenems, rifampicin or azithromycin are synergistic against these strains despite in-vitro resistance to these agents alone. The use of antimicrobial combinations have therefore been advocated for the treatment of severe A. baumannii infection in man. In order to determine whether such combinations are synergistic against the prevalent clones of multi-drug resistant A. baumannii causing infection in the UK, we performed synergy testing against representative isolates using two rapid Etest methods. METHODS: The activity of polymyxin in combination with imipenem, azithromycin or rifampicin was assessed against five strains of multi-drug resistant A. baumannii encoding OXA-23 carbapenemases. Synergy studies were performed by Etest-agar dilution and a combined Etest strip method. Synergy was defined as a FICI of < or = 0.5. RESULTS: All strains were resistant to beta-lactams, carbapenems, quinolones and aminoglycosides but susceptible to polymyxins. Marked synergy was not seen with polymyxin in combination with imipenem, rifampicin or azithromycin against any of the strains. Borderline synergy (FICI = 0.5) was seen against one strain belonging to OXA-23 clonal group 2, using the Etest-agar dilution method only. CONCLUSION: In-vitro synergy with polymxyin in combination with imipenem, rifampicin or azithromycin is highly strain and method dependent. As reliable synergy could not be demonstrated against the prevalent UK multi-drug resistant strains, use of such combinations should not be used for empirical treatment of these infections in the UK. The optimal treatment for serious multi-drug A. baumannii infection and the role of combination therapy should be addressed in a prospective clinical trial.

Acinetobacter baumannii↗
PubMed2026

Acinetobacter guillouiae, a lipolytic strain isolated from sludge capable of partially depolymerising polyethylene terephthalate: genomic, proteomic, and biochemical insights.

Acinetobacter guillouiae I-MWF was isolated by incubating amorphous polyethylene terephthalate (PET) film in sludge samples. The strain partially depolymerised PET powder with 11.3% crystallinity, as confirmed by FT-IR, HPLC-UV, and LC-MS analyses. Extracellular enzymes released terephthalic acid (TPA), mono(2-hydroxyethyl) terephthalate (MHET), and bis(2-hydroxyethyl) terephthalate (BHET). Genomic analysis identified 18 putative extracellular hydrolases, including lipases and esterases, each with a conserved catalytic triad. Proteomic profiling revealed expression of two triacylglycerol lipases and two additional lipase-family proteins when the strain was cultivated with PET or a PET-Tween 80 mixture. These enzymes were cloned in Escherichia coli, but most formed insoluble, inactive inclusion bodies, and one was not expressed. Molecular modelling highlighted structural features likely to influence their catalytic interaction with PET. Although the strain partially depolymerised PET powder, it was unable to grow on PET, TPA, or ethylene glycol, indicating that PET depolymerisation occurs as a side activity rather than supporting growth. Instead, A. guillouiae displayed strong lipolytic activity and a clear preference for lipid-based substrates, achieving its highest growth with Tween 80. A lipid transporter was also expressed under these conditions, suggesting adaptation to hydrocarbon-rich environments. These findings indicate that A. guillouiae I-MWF can mediate partial PET depolymerisation without assimilating the resulting monomers, while preferentially growing on lipid-like substrates.

Acinetobacter↗
PubMed1991

Occurrence of L-2,4-diaminobutyrate decarboxylase activity in Acinetobacter.

Three strains of the genus Acinetobacter grown in a polyamine-free synthetic medium contained very high amounts of 1,3-diaminopropane, and there were also high concentrations in the extracellular growth medium. Little, if any, of the usual polyamines, putrescine, spermidine and spermine were found. There was no detectable activity of aminopropyltransferase (greater than 0.2 nmol spermidine formed/mg protein/h), which would be responsible for the formation of spermidine or spermine, expected precursors of 1,3-diaminopropane. These observations suggested the possibility of another mode of 1,3-diaminopropane biogenesis. Decarboxylation activity towards L-2,4-diaminobutyrate leading to the formation of 1,3-diaminopropane was detected in extracts of all three strains examined. The decarboxylase was partially purified from A. calcoaceticus ATCC 23055. The enzyme was active against only L-2,4-diaminobutyrate among the diamino acids tested and required pyridoxal phosphate as a cofactor. Mg2+ activated the enzyme.

Acinetobacter↗
PubMed1990

Native valve endocarditis caused by Acinetobacter calcoaceticus subspecies lwoffi.

A case of native valve endocarditis due to Acinetobacter calcoaceticus in a patient with dental caries is presented. The aortic, mitral and tricuspid valves were affected and showed vegetation by echocardiography in the affected valves. In spite of a good response to antibiotic therapy, multiple embolisms resulted in the patient's death. An autopsy confirmed the vegetation, which was calcified and contained no bacteria.

Acinetobacter Infections↗
PubMed1993

Isolation of Acinetobacter calcoaceticus from the gastrointestinal tracts of SCID mice.

Acinetobacter calcoaceticus colonization was observed in the gastrointestinal tracts of C.-B17-scid/scid (SCID) mice, while it was not observed in C.B17-scid/+ and C.B17-+/+ mice with normal immunity housed under the same conditions. A. calcoaceticus and other viable enteric bacteria were not isolated from any organs other than gastrointestinal tract in SCID mice. The mice colonized with this organism were apparently healthy and no significant visceral lesion was observed.

Acinetobacter calcoaceticus↗
PubMed2006

Production of alpha, omega-alkanediols using Escherichia coli expressing a cytochrome P450 from Acinetobacter sp. OC4.

Our biotransformation using Escherichia coli expressing a cytochrome P450 (CYP) belonging to the CYP153A family from Acinetobacter sp. OC4 produced a great amount of 1-octanol (2,250 mg per liter) from n-octane after 24 h of incubation. This level of production is equivalent to the maximum level previously achieved in biotransformation experiments of alkanes. In addition, the initial production rate of 1-octanol was maintained throughout the entire incubation period. These results indicate that we have achieved the functional and stable expression of a CYP in E. coli for the first time. Further, our biotransformation system showed alpha,omega-diterminal oxidation activity of n-alkanes, and a large amount of 1,8-octanediol (722 mg per liter) was produced from 1-octanol after 24 h of incubation. This is the first report on the bioproduction of alpha,omega-alkanediols from n-alkanes or 1-alkanols.

Acinetobacter↗
PubMed1996

Cloning of catBCIJFD genes for catechol degradation into chromosomal pobA and genetic stability of the recombinant Acinetobacter calcoaceticus.

A possible obstacle in the development of hybrid strains of Acinetobacter calcoaceticus by the introduction of a metabolic pathway into the chromosome is genetic instability of the resulting recombinant strains. Therefore, the possibility that the pobA gene can be used as a chromosomal cloning site where the transposed genes can be maintained and expressed, was explored in this study. For this purpose, two model hybrid strains of A. calcoaceticus were created, in which a DNA fragment carrying catBCIJFD genes for catabolic degradation of catechol was inserted into pobA in opposite directions of each other, and their genetic stabilities were experimentally examined. Our data demonstrated that the stability of the genes neighboring the insertions depends on the orientations of the insertions. Also, the data further indicated that the functional metabolic pathways introduced into pobA can be expressed successfully as far as the insertion is engineered in an appropriate way. Concurrently, it was proposed that the pobA can be used as a chromosomal cloning site, and that introduction of an useful metabolic pathway into pobA may offer considerable promise to the construction of a hybrid strain with improved metabolic capabilities.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1999

Purification and characterization of a novel extracellular lipase catalyzing hydrolysis of oleyl benzoate from Acinetobacter nov. sp. strain KM109.

A new lipase (OBase) which efficiently hydrolyzes oleyl benzoate (OB) was found in the culture supernatant of Acinetobacter nov. sp. strain KM109, a new isolate growing in a minimum medium containing OB as the sole carbon source. OBase was purified to homogeneity with 213-fold purification and 0.8% yield. The molecular weight was estimated to be 62,000 +/- 1,000 by SDS-PAGE under denatured-reduced conditions and to be 50,000 +/- 1,000 by gel-filtration HPLC under native conditions; these findings indicate that OBase is a monomeric enzyme. The optimum temperature and pH of OBase were about 45 degrees C and pH 8. Temperature and pH stabilities were at or lower than 35 degrees C and in a range of pH 6-8, respectively. Purified OBase preferentially hydrolyzed p-nitrophenyl benzoate (pNPB) over p-nitrophenyl acetate (pNPA) or p-nitrophenyl caproate (pNPC) [pNPB/pNPA = 20 and pNPB/pNPC = 5.4], indicating that OBase has a high affinity for benzoyl esters. Partial amino-acid sequences of OBase fragments obtained after lysyl endopeptidase treatment showed no similarity with known proteins.

Acinetobacter↗
PubMed2002

Microbial degradation of lipid by Acinetobacter sp. strain SOD-1.

Acinetobacter sp. strain SOD-1, capable of rapidly degrading salad oil, was isolated from soil. Strain SOD-1 showed good growth and degraded 68.7+/-2.7 and 83.0% of an initial 3000 ppm salad oil suspension in 24 h at 20 degrees C and pH 7.0 and at 35 degrees C and pH 8.0, respectively. The degradation rate depended on pH, temperature, phosphate concentration, and initial cell density.

Acinetobacter↗
PubMed2002

Primary structure and catalytic properties of a cold-active esterase from a psychrotroph, Acinetobacter sp. strain No. 6. isolated from Siberian soil.

We cloned a gene coding for a cold-active esterase from a genomic library of Acinetobacter sp. strain No. 6, a psychrotroph isolated from Siberian soil. The gene, aest, encoded a protein of 301 amino acid residues, the deduced sequence of which had less than 17% identity to sequences of known esterases and lipases. However, the esterase seemed to belong to the alpha/beta hydrolase superfamily, because it contained a sequence, Gly-Xaa-Ser-Xaa-Gly (with Xaa an arbitrary amino acid residue), found in most serine hydrolases of this superfamily. Sequence comparison earlier suggested a weak phylogenetic relationship of gene product AEST to the EST group of the esterase-lipase family, which has been found only in eukaryotes. The aest gene was expressed in Escherichia coli BL21(DE3) cells under the control of the T7 promoter, and the expression product was purified to homogeneity and characterized. It catalyzed the hydrolysis of esters with short-chain acyl groups and had lower activation energy and lower thermostability than do mesophilic enzymes, as expected from the cold-adapted nature of this enzyme.

Acinetobacter↗