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At least 811 records · Page 45Linked to original sources
PubMed2003

A low molecular weight enterotoxic hemolysin from clinical Enterobacter cloacae.

Seven of 50 Enterobacter cloacae strains from clinical isolates produced small turbid zones of hemolysis in horse and sheep blood agar plates, and the culture supernatants were also positive for hemolytic activity. The hemolysin was partially purified from the culture supernatant of E. cloacae by ultrafiltration (PM-10 membrane) and extraction with acetone. Semipurified hemolysin was stable to heating (100 degrees C, 30 min) and was soluble in organic solvents (acetone, ethanol, and methanol). The toxin showed no loss of biological activity after treatment with trypsin and was stable to acid treatment at pH 2.0 but not at a pH greater than 7.0. In the rat intestinal loop assay, the hemolysin caused hemorrhagic fluid accumulation and severe histological alterations. These findings indicate that this hemolysin may be a putative virulence factor in E. cloacae infections.

Agar↗
PubMed2006

Effect of some environmental parameters on fermentative hydrogen production by Enterobacter cloacae DM11.

Fermentative hydrogen production was carried out by Enterobacter cloacae DM11, using glucose as the substrate. The effects of initial substrate concentration, initial medium pH, and temperature were investigated. Results showed that at an initial glucose concentration of 1.0% (m/v), the molar yield of hydrogen was 3.31 mol (mol glucose)(-1). However, at higher initial glucose concentration, both the rate and cumulative volume of hydrogen production decreased. The pH of 6.5 +/- 0.2 at a temperature of 37 degrees C was found most suitable with respect to maximum rate of production of hydrogen in batch fermentation. Activation enthalpies of fermentation and that of thermal deactivation of the present process were estimated following a modified Arrhenius equation. The values were 47.34 and 118.67 kJ mol(-1) K(-1), respectively. The effect of the addition of Fe(2+) on hydrogen production was also studied. It revealed that the presence of iron (Fe(2+)) in the media up to a concentration of 20 mg L(-1) had a marginal enhancing effect on total hydrogen production. A simple model developed from the modified Gompertz equation was applied to estimate the hydrogen production potential, production rate, and lag-phase time in a batch process, based on the cumulative hydrogen production curves, using the software program Curve Expert 1.3.

Enterobacter cloacae↗
PubMed1983

Combined defibrinated human blood and antimicrobial drug activities against Enterobacter cloacae.

The combinations of 11 antimicrobial drugs and fresh human defibrinated blood were examined for potential additive effects against several isolates of Enterobacter cloacae recovered from patients with bacteremia or meningitis. Aminoglycosides (amikacin, gentamicin, netilmicin) proved most efficacious, followed by cephalosporins (lamoxactam, cefotaxime, ceftizoxime) and ureidopenicillins (mezlocillin, piperacillin). Nalidixic acid, nitrofurantoin, and cotrimoxazole yielded indifferent effects. The E. cloacae isolates displayed low virulence for outbred NMRI mice.

Animals↗
PubMed1984

Characterization of two clinical, multiple-drug-resistant isolates of Enterobacter cloacae.

Two multiple drug resistant Enterobacter cloacae isolates (Nos. 460 and 493) varied phenotypically in bacteriocin susceptibility in the absence of significant O antigen variation. Both isolates were susceptible to chloramphenicol, nitrofurantoin, polymyxin B, nalidixic acid, norfloxacin, and enoxacin only. One isolate carried a non-conjugative resistance (R) plasmid, whereas the other isolate contained a conjugative, 'curable' R plasmid and a cryptic plasmid. Both wild-type isolates constitutively produced a chromosomal cephalosporinase (nitrocefin hydrolysis); 'cured' variants of E. cloacae isolate No. 493, which had become susceptible for lamoxactam, produced a cefazolin-inducible beta-lactamase. The two E. cloacae isolates, including their 'cured' variants, were of low-grade virulence for outbred NMRI mice. Both isolates differed somewhat in susceptibility to defibrinated human blood. Inhibitory (0.25 microgram/ml), but not subinhibitory (0.125 microgram/ml) concentrations of norfloxacin and enoxacin combined with human blood yielded additive effects against both E. cloacae isolates.

Adult↗
PubMed1987

Selection frequency of resistant variants by various beta-lactam antibiotics in clinical Enterobacter cloacae isolates.

The frequency of selection of resistant variants by 10 different broad-spectrum beta-lactam derivatives was evaluated for 10 clinical Enterobacter cloacae isolates. With respect to most penams or cephems, resistant variants could be selected up to 8- or 32-fold the MIC, respectively. However, with cefpirome as the selecting agent resistant variants were obtained only at twice the MIC, whereas resistant variants were barely detectable with temocillin and not detectable in any case with imipenem. The variants exhibited cross-resistance between penams and cephems including aztreonam, but not to temocillin and imipenem regardless of the beta-lactamase amount produced. Enzyme production of the variants ranged from 0.2 U to 19.0 U beta-lactamase/mg protein of the cell-free supernatants. Moreover, analysis of the outer membrane protein composition did not reveal marked alterations between wild strains and the corresponding variants. It is evident that 'overproduction of the chromosomal beta-lactamase' cannot explain entirely phenotypic resistance to broad-spectrum beta-lactam compounds, but a lack of porin production, i.e., major outer membrane proteins, cannot provide an explanation for the above findings.

Anti-Bacterial Agents↗
PubMed1991

Carbapenem resistance in Enterobacter aerogenes is due to lipopolysaccharide alterations.

The extensive characterization of 2 clinical Enterobacter aerogenes isolates resistant to all beta-lactam antibiotics including imipenem revealed that imipenem resistance could not be attributed to overproduction of the chromosomal beta-lactamase; moreover, it was lost after subcultivation and can be thus considered as unstable. The comparison of sensitive and resistant clones revealed that the beta-lactamase in the resistant clones was less inducible in the resistant clones and moreover, there was an altered 2-keto-3-deoxyoctonate/carbohydrate ratio in the resistant clones as compared to the imipenem-sensitive clones, thus suggesting alterations in the lipopolysaccharide (LPS). Neither enzymatic degradation of both imipenem and meropenem nor alterations of the outer membrane proteins could be observed. These findings make it apparent that this type of resistance is likely due to an impaired uptake of the agents due to LPS alterations.

Bacterial Outer Membrane Proteins↗
PubMed1991

Variation in induction of chromosomal beta-lactamase expression in strains of Enterobacter cloacae.

Eight strains of Enterobacter cloacae with varying patterns of susceptibility to beta-lactam antibiotics were studied to compare the inducibility and expression of their beta-lactamase genes. These strains included two isolates from one patient, which differed in their susceptibility to cefamandole. A resistant strain constitutively produced large amounts of beta-lactamase; a sensitive strain produced an inducible beta-lactamase. Study of induction and growth characteristics of all strains revealed that the induction and the expression of inducible beta-lactamase genes may vary considerably among strains of E. cloacae.

Adult↗
PubMed1992

Exposure effects of netilmicin on Enterobacter cloacae clinical isolates.

The effects of netilmicin exposure on two aminoglycoside (AMG)-resistant and two AMG-susceptible Enterobacter cloacae isolates were studied. It was found that 1 h incubation of bacterial suspensions with netilmicin at 16 mg/l reduces the amounts of lipopolysaccharides present on the bacterial surface. Also, netilmicin pretreatment increased both the susceptibility to normal human serum and the adhesion to human epithelial cells of all four E. cloacae strains examined.

Bacterial Adhesion↗
PubMedDate not supplied

Effect of beta-lactamase expression on susceptibility of local isolates of Enterobacter cloacae, Serratia marcescens and Pseudomonas aeruginosa to beta-lactam antibiotics.

During surveillance studies, a total of 66 strains of gram-negative bacilli (28 Enterobacter cloacae, 20 Serratia marcescens and 18 Pseudomonas aeruginosa) with a reduced susceptibility to third-generation cephalosporins, aztreonam and amikacin were isolated from documented infections. All isolates were highly susceptible to imipenem and sparfloxacin. beta-Lactamase activity was demonstrated in all isolates of E. cloacae and S. marcescens, and in 77% of P. aeruginosa isolates. Inducible beta-lactamase activity was detected in 80, 65 and 40% of E. cloacae, S. marcescens and P. aeruginosa isolates, respectively, when cefoxitin was used as an inducer. More inducible beta-lactamase producers were observed when imipenem was used as an inducer. Isolates of E. cloacae, and to a lesser extent S. marcescens, expressed a wide spectrum of beta-lactamase activities. There was a good correlation between baseline beta-lactamase activity and the respective MIC of ceftazidime, cefotaxime and ceftriaxone, and to a lesser extent aztreonam in E. cloacae and S. marcescens isolates. Only one isolate of E. cloacae demonstrated an extended beta-lactamase activity. The data suggest that the resistance of E. cloacae and S. marcescens isolates to beta-lactam antibiotics is largely dependent upon hyperproduction of beta-lactamase.

Anti-Bacterial Agents↗
PubMed1991

Enterobacter cloacae bacteremia in children: a review of 30 cases in 12 years.

A review was performed of the 30 cases of pediatric Enterobacter cloacae (EBC) bacteremia which occurred at our institution during a 12-year period. These 30 cases represented 88% of all cases in which EBC was isolated by blood culture (four other instances were considered contaminants); the rate of isolation of this organism relative to all positive blood cultures was 0.6%. There were 14 patients less than 12 months of age, with 10 less than 2 months of age. Infection was nosocomially-acquired in 17 cases. At the time the positive blood culture was obtained, 5 patients were afebrile, and 8 patients (five immunocompromised) had been receiving parenteral antibiotic therapy to which the organism exhibited in-vitro sensitivity for at least 24 hours. EBC was a constituent of polymicrobial bacteremia in 6 cases; in 5 instances the associated organisms were also gram-negative bacteria. There were a total of 33 underlying medical conditions or foci of infection associated with EBC bacteremia identified in 27 patients, the most common of which were immune-deficiency state (17) and gastrointestinal tract lesions (6). There were 3 patients who died. EBC bacteremia is a relatively rare pediatric infection. It is commonly nosocomially-acquired, and afflicts children who are younger-aged or compromised by underlying medical problems.

Anti-Bacterial Agents↗
PubMed1999

Extended-spectrum beta-lactamase producing strains of Enterobacter cloacae transferring resistance to cefotaxime and ceftazidime.

Transferability of ceftazidime resistance and of extended-spectrum beta-lactamase (ESBL) production was recorded in three strains of Enterobacter cloacae from Frankfurt University Clinics. All three strains were resistant to rifampicin, carbenicillin, cephaloridine, cefotaxime, ceftazidime, aztreonam, imipenem and meropenem. They transferred directly determinants of resistance to carbenicillin and cephaloridine to Escherichia coli K-12 No. 185 nal+ recipient strain. All transconjugant colonies also contained determinants of resistance to cefotaxime, ceftazidime and aztreonam. In the second cycle of transfers, determinants of resistance to carbenicillin, cephaloridine, cefotaxime, ceftazidime and aztreonam were transferred en bloc to the recipient Escherichia coli K-12 No. 3110 rif+ indicating that the "transfer factor" (tra+) mediating the process of conjugational transfer had also been co-transferred. Double-disk diffusion test showed the same pattern of production of ESBLs both in original strains and in transconjugants. Transfer of cefotaxime, ceftazidime and aztreonam was accompanied by the transfer of ESBL production.

Cefotaxime↗
PubMed2004

Extended-Spectrum beta-lactamase (ESBL) producing Enterobacter aerogenes phenotypically misidentified as Klebsiella pneumoniae or K. terrigena.

BACKGROUND: Enterobacter aerogenes and Klebsiella pneumoniae are common isolates in clinical microbiology and important as producers of extended spectrum beta-lactamases (ESBL). The discrimination between both species, which is routinely based on biochemical characteristics, is generally accepted to be straightforward. Here we report that genotypically unrelated strains of E. aerogenes can be misidentified as K. pneumoniae by routine laboratories using standard biochemical identification and using identification automates. RESULTS: Ten clinical isolates, identified as K. pneumoniae or K. terrigena with the routinely used biochemical tests and with API-20E, were identified as E. aerogenes by tDNA-PCR - an identification that was confirmed by 16S rRNA gene sequencing for five of these isolates. Misidentification also occurred when using the automated identification systems Vitek 2 and Phoenix, and was due to delayed positivity for ornithine decarboxylase and motility. Subculture and prolonged incubation resulted in positive results for ornithine decarboxylase and for motility. It could be shown by RAPD-analysis that the E. aerogenes strains belonged to different genotypes. CONCLUSIONS: Clinical E. aerogenes isolates can be easily misidentified as Klebsiella due to delayed positivity for ornithine decarboxylase and motility. The phenomenon may be widespread, since it was shown to occur among genotypically unrelated strains from different hospitals and different isolation dates. A useful clue for correct identification is the presence of an inducible beta-lactamase, which is highly unusual for K. pneumoniae. In several instances, the use of genotypic techniques like tDNA-PCR may circumvent problems of phenotypic identification.

Bacterial Typing Techniques↗
PubMed2000

Cloning and characterization of the ddc homolog encoding L-2,4-diaminobutyrate decarboxylase in Enterobacter aerogenes.

L-2,4-diaminobutyrate decarboxylase (DABA DC) catalyzes the formation of 1,3-diaminopropane (DAP) from DABA. In the present study, the ddc gene encoding DABA DC from Enterobacter aerogenes ATCC 13048 was cloned and characterized. Determination of the nucleotide sequence revealed an open reading frame of 1470 bp encoding a 53659-Da protein of 490 amino acids, whose deduced NH2-terminal sequence was identical to that of purified DABA DC from E. aerogenes. The deduced amino acid sequence was highly similar to those of Acinetobacter baumannii and Haemophilus influenzae DABA DCs encoded by the ddc genes. The lysine-307 of the E. aerogenes DABA DC was identified as the pyridoxal 5'-phosphate binding residue by site-directed mutagenesis. Furthermore, PCR analysis revealed the distribution of E. aerogenes ddc homologs in some other species of Enterobacteriaceae. Such a relatively wide occurrence of the ddc homologs implies biological significance of DABA DC and its product DAP.

Amino Acid Sequence↗
PubMed1992

Continuous chitosan hydrolyzate production by immobilized chitosanolytic enzyme from Enterobacter sp. G-1.

Chitosanolytic enzymes from Enterobacter sp. G-1 were immobilized on various carriers to continuously hydrolyze chitosan. Four different carriers were tested: FE-3901 (strong basic anion exchange resin, ionic binding), glutaraldehyde-treated FE-4612 (weak basic anion exchange resin, cross-linking), Chitopearl (chitosan beads), and alginate calcium. Glutaraldehyde-treated FE-4612 and Chitopearl immobilized more protein than the others. The enzyme immobilized on FE-3901 had the greatest activity. The activity of enzyme immobilized on FE-3901 decreased rapidly when exposed to a continuous flow of 1% chitosan. The enzyme immobilized with Chitopearl retained more than 50% of its original activity after 17 days, and the activity was fully restored by re-immobilization.

Anion Exchange Resins↗
PubMed1994

Molecular cloning and nucleotide sequence of the beta-galactosidase gene from Enterobacter cloacae GAO.

The gene encoding a beta-galactosidase from Enterobacter cloacae GAO was cloned and expressed in Escherichia coli. The nucleotide sequence of the insert of a positive clone had an open reading frame of 3084 bp that encoded a polypeptide of 1028 amino acid residues with a calculated molecular mass of 116,677 daltons. The amino acid sequence of beta-galactosidase deduced from the nucleotide sequence, especially the sequence around the putative active site and of the fourteen regions, showed significant homology to beta-galactosidases of other microorganisms, E. coli, Klebsiella pneumoniae, Lactobacillus bulgaricus, and Clostridium acetobutylicum.

Amino Acid Sequence↗
PubMed1995

Enzymatic synthesis of L-tryptophan by Enterobacter aerogenes tryptophanase highly expressed in Escherichia coli, and some properties of the purified enzyme.

We constructed two plasmids that have a strong tac promoter and a structural gene for tryptophanase of Enterobacter aerogenes SM-18 (pKT901EA) or Escherichia coli K-12 (pKT951EC). The tryptophanase activity of E. coli JM109 transformed with pKT901EA (JM109/pKT901EA) was inducible with isopropyl-beta-D-thiogalactopyranoside, and 3.6 times higher than that of E. aerogenes SM-18. Cells of JM109/pKT901EA induced for tryptophanase synthesized L-tryptophan from indole, ammonia, and pyruvate more efficiently than E. aerogenes SM-18. Although JM109/pKT951EC expressed a similar level of tryptophanase activity to that of JM109/pKT901EA, the synthesis of L-tryptophan by the cells of JM109/pKT951EC did not proceed well compared with JM109/pKT901EA. Tryptophanases from E. aerogenes and E. coli K-12 were purified, and their properties were investigated. The purified E. aerogenes tryptophanase showed higher stability against heat inactivation than E. coli tryptophanase.

Enterobacter↗
PubMed1995

Purification and characterization of extracellular alginate lyase from Enterobacter cloacae M-1.

An alginate lyase from the culture supernatant of Enterobacter cloacae M-1 was purified by ammonium sulfate precipitation, cation-exchange chromatography (SP-Toyopearl), and gel filtration (Ultrogel AcA44). The final preparation thus obtained showed a single band on SDS-PAGE. The purified enzyme had the molecular weight of 38,000 and 32,000 by SDS-PAGE and gel filtration, respectively. The pI of the enzyme was 8.9. The optimum pH and temperature for the enzyme reaction were around 7.8 and 30 degrees C, respectively. The enzyme was unstable on heating. EDTA completely inhibited the enzyme activity, but the activity was completely restored by the treatment with CaCl2. The enzyme was specific for poly-guluronate and produced several kinds of unsaturated oligomers from the gluluronate. This suggested that the enzyme could be classified as an endo poly-guluronate lyase.

Amino Acid Sequence↗