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1.  Successive Emergence of Enterobacter aerogenes Strains Resistant to Imipenem and Colistin in a Patient 
Enterobacter aerogenes is an agent of hospital-acquired infection that exhibits a remarkable resistance to β-lactam antibiotics during therapy. Five successive isolates of E. aerogenes infecting a patient and exhibiting a multiresistance phenotype to β-lactam antibiotics and fluoroquinolones were investigated. Among these clinical strains, four presented resistant phenotypes during successive imipenem and colistin treatments. The involved resistance mechanisms exhibited by the successive isolates were associated with alterations of the outer membrane that caused a porin decrease and lipopolysaccharide modifications.
PMCID: PMC1068582  PMID: 15793111
2.  Aeromonas popoffii Urinary Tract Infection 
Journal of Clinical Microbiology  2004;42(11):5427-5428.
Aeromonas popoffii is a recently described species isolated mainly from freshwater. An isolate of Aeromonas popoffii was found to be responsible for a urinary tract infection in a 13-year-old boy suffering from spina bifida with enterocystoplasty. This is the first reported case of human infection attributed to this species.
PMCID: PMC525237  PMID: 15528763
3.  RamA Is an Alternate Activator of the Multidrug Resistance Cascade in Enterobacter aerogenes 
Multidrug resistance (MDR) in Enterobacter aerogenes can be mediated by induction of MarA, which is triggered by certain antibiotics and phenolic compounds. In this study, we identified the gene encoding RamA, a 113-amino-acid regulatory protein belonging to the AraC-XylS transcriptional activator family, in the Enterobacter aerogenes ATCC 13048 type strain and in a clinical multiresistant isolate. Overexpression of RamA induced an MDR phenotype in drug-susceptible Escherichia coli JM109 and E. aerogenes ATCC 13048, as demonstrated by 2- to 16-fold-increased resistance to β-lactams, tetracycline, chloramphenicol, and quinolones, a decrease in porin production, and increased production of AcrA, a component of the AcrAB-TolC drug efflux pump. We show that RamA enhances the transcription of the marRAB operon but is also able to induce an MDR phenotype in a mar-deleted strain. We demonstrate here that RamA is a transcriptional activator of the Mar regulon and is also a self-governing activator of the MDR cascade.
PMCID: PMC434192  PMID: 15215103
4.  Omp35, a New Enterobacter aerogenes Porin Involved in Selective Susceptibility to Cephalosporins 
In Enterobacter aerogenes, β-lactam resistance often involves a decrease in outer membrane permeability induced by modifications of porin synthesis. In ATCC 15038 strain, we observed a different pattern of porin production associated with a variable antibiotic susceptibility. We purified Omp35, which is expressed under conditions of low osmolality and analyzed its pore-forming properties in artificial membranes. This porin was found to be an OmpF-like protein with high conductance values. It showed a noticeably higher conductance compared to Omp36 and a specific location of WNYT residues in the L3 loop. The importance of the constriction region in the porin function suggests that this organization is involved in the level of susceptibility to negative large cephalosporins such as ceftriaxone by bacteria producing the Omp35 porin subfamily.
PMCID: PMC415628  PMID: 15155215
5.  Corynebacterium freneyi Bacteremia 
Journal of Clinical Microbiology  2003;41(6):2777-2778.
Corynebacterium freneyi is a recently described alpha-glucosidase-positive species of the genus Corynebacterium. To our knowledge, there is no description of human infection due to this species. We report on a case of bacteremia due to C. freneyi following vascular surgery.
PMCID: PMC156481  PMID: 12791929
6.  Eubacterium callanderi Bacteremia: Report of the First Case 
Journal of Clinical Microbiology  2003;41(5):2235-2236.
Eubacterium callanderi is an environmental anaerobic rod-shaped bacterium first isolated in 1998 from an industrial anaerobic digester. We report on the first clinical isolate of E. callanderi, which was recovered from the blood of a patient with a bladder carcinoma. Identification of the organism was made by cell fatty acid chromatographic analysis and 16S rRNA gene sequencing.
PMCID: PMC154684  PMID: 12734289
7.  prbA, a Gene Coding for an Esterase Hydrolyzing Parabens in Enterobacter cloacae and Enterobacter gergoviae Strains 
Journal of Bacteriology  2002;184(18):5011-5017.
The new gene prbA encodes an esterase responsible for the hydrolysis of the ester bond of parabens in Enterobacter cloacae strain EM. This gene is located on the chromosome of strain EM and was cloned by several PCR approaches. The prbA gene codes for an immature protein of 533 amino acids, the first 31 of which represent a proposed signal peptide yielding a mature protein of a putative molecular mass of 54.6 kDa. This enzyme presents analogies with other type B carboxylesterases, mainly of eukaryotic origin. The cloning and expression of the prbA gene in a strain of Escherichia coli previously unable to hydrolyze parabens resulted in the acquisition of a hydrolytic capacity comparable to the original activity of strain EM, along with an increased resistance of the transformed strain to methyl paraben. The presence of homologues of prbA was tested in additional ubiquitous bacteria, which may be causative factors in opportunistic infections, including Enterobacter gergoviae, Enterobacter aerogenes, Pseudomonas agglomerans, E. coli, Pseudomonas aeruginosa, and Burkholderia cepacia. Among the 41 total strains tested, 2 strains of E. gergoviae and 1 strain of Burkholderia cepacia were able to degrade almost completely 800 mg of methyl paraben liter−1. Two strains of E. gergoviae, named G1 and G12, contained a gene that showed high homology to the prbA gene of E. cloacae and demonstrated comparable paraben esterase activities. The significant geographical distance between the locations of the isolated E. cloacae and E. gergoviae strains suggests the possibility of an efficient transfer mechanism of the prbA gene, conferring additional resistance to parabens in ubiquitous bacteria that represent a common source of opportunistic infections.
PMCID: PMC135325  PMID: 12193616
8.  mar Operon Involved in Multidrug Resistance of Enterobacter aerogenes 
We determined the sequence of the entire marRAB operon in Enterobacter aerogenes. It is functionally and structurally analogous to the Escherichia coli operon. The overexpression of E. aerogenes MarA induces a multidrug resistance phenotype in a susceptible strain, demonstrated by a noticeable resistance to various antibiotics, a decrease in immunodetected porins, and active efflux of norfloxacin.
PMCID: PMC127096  PMID: 11897595
9.  16S Ribosomal DNA Sequence Analysis of a Large Collection of Environmental and Clinical Unidentifiable Bacterial Isolates 
Journal of Clinical Microbiology  2000;38(10):3623-3630.
Some bacteria are difficult to identify with phenotypic identification schemes commonly used outside reference laboratories. 16S ribosomal DNA (rDNA)-based identification of bacteria potentially offers a useful alternative when phenotypic characterization methods fail. However, as yet, the usefulness of 16S rDNA sequence analysis in the identification of conventionally unidentifiable isolates has not been evaluated with a large collection of isolates. In this study, we evaluated the utility of 16S rDNA sequencing as a means to identify a collection of 177 such isolates obtained from environmental, veterinary, and clinical sources. For 159 isolates (89.8%) there was at least one sequence in GenBank that yielded a similarity score of ≥97%, and for 139 isolates (78.5%) there was at least one sequence in GenBank that yielded a similarity score of ≥99%. These similarity score values were used to defined identification at the genus and species levels, respectively. For isolates identified to the species level, conventional identification failed to produce accurate results because of inappropriate biochemical profile determination in 76 isolates (58.7%), Gram staining in 16 isolates (11.6%), oxidase and catalase activity determination in 5 isolates (3.6%) and growth requirement determination in 2 isolates (1.5%). Eighteen isolates (10.2%) remained unidentifiable by 16S rDNA sequence analysis but were probably prototype isolates of new species. These isolates originated mainly from environmental sources (P = 0.07). The 16S rDNA approach failed to identify Enterobacter and Pantoea isolates to the species level (P = 0.04; odds ratio = 0.32 [95% confidence interval, 0.10 to 1.14]). Elsewhere, the usefulness of 16S rDNA sequencing was compromised by the presence of 16S rDNA sequences with >1% undetermined positions in the databases. Unlike phenotypic identification, which can be modified by the variability of expression of characters, 16S rDNA sequencing provides unambiguous data even for rare isolates, which are reproducible in and between laboratories. The increase in accurate new 16S rDNA sequences and the development of alternative genes for molecular identification of certain taxa should further improve the usefulness of molecular identification of bacteria.
PMCID: PMC87447  PMID: 11015374
10.  Characterization of Plasmid-Borne and Chromosome-Encoded Traits of Agrobacterium Biovar 1, 2, and 3 Strains from France 
We collected 111 Agrobacterium isolates from galls of various origins (most of them from France) and analyzed both their plasmid-borne and chromosome-encoded traits. Phenotypic analysis of these strains allowed their classification in three phena which exactly matched the delineation of biovars 1, 2, and 3. A fourth phenon was identified which comprises three atypical strains. The phenotypic analysis has also allowed us to identify 12 additional characteristics which could be used to identify the three biovars of Agrobacterium. Our results also suggest that biovar 1 and 2 represent distinct species. Analysis of plasmid-borne traits confirmed that tartrate utilization is a common feature of biovar 3 strains (now named Agrobacterium vitis) and of Agrobacterium grapevine strains in general. Among pathogenic strains of Agrobacterium, several exhibited unusual opine synthesis and degradation patterns, and one strain of biovar 3 induced tumors containing vitopine and a novel opine-like molecule derived from putrescine. We have named this compound ridéopine.
PMCID: PMC101418  PMID: 10788345
11.  Imipenem Resistance of Enterobacter aerogenes Mediated by Outer Membrane Permeability 
Journal of Clinical Microbiology  2000;38(3):1048-1052.
Multidrug-resistant Enterobacter aerogenes strains are increasingly isolated in Europe and especially in France. Treatment leads to imipenem resistance, because of a lack of porin. We studied the evolution of resistance in 29 strains isolated from four patients during their clinical course. These strains belonged to the prevalent epidemiological type observed in France in previous studies (C. Bosi, et al., J. Clin. Microbiol. 37:2165–2169, 1999; A. Davin-Regli et al., J. Clin. Microbiol. 34:1474–1480, 1996). They also harbored a TEM-24 extended-spectrum β-lactamase-coding gene. Thirteen strains were susceptible to gentamicin and resistant to imipenem and cefepime. All of the patients showed E. aerogenes strains with this resistance after an imipenem treatment. One patient showed resistance to imipenem after a treatment with cefpirome. Twelve of these 13 strains showed a lack of porin. Cessation of treatment with imipenem for three patients was followed by reversion of susceptibility to this antibiotic and the reappearance of porins, except in one case. For one patient, we observed three times in the same day the coexistence of resistant strains lacking porin and susceptible strains possessing porin. The emergence of multidrug-resistant E. aerogenes strains is very disquieting. In our study, infection by E. aerogenes increased the severity of the patients' illnesses, causing a 100% fatality rate.
PMCID: PMC86335  PMID: 10698994
12.  Molecular Identification of a Nocardiopsis dassonvillei Blood Isolate 
Journal of Clinical Microbiology  1999;37(10):3366-3368.
Nocardiopsis dassonvillei is an environmental aerobic actinomycete seldom isolated in cutaneous and pulmonary infections. We herein report the first N. dassonvillei blood isolate in a patient hospitalized for cholangitis. Although morphological characteristics and biochemical tests allowed a presumptive identification of this isolate, cell wall fatty acid chromatographic analysis confirmed identification at the genus level, and 16S rRNA gene sequencing achieved definite identification. This study illustrates the usefulness of 16S rRNA gene sequencing as a routine method for the identification of actinomycetes.
PMCID: PMC85569  PMID: 10488208
13.  Most Enterobacter aerogenes Strains in France Belong to a Prevalent Clone 
Journal of Clinical Microbiology  1999;37(7):2165-2169.
The aim of this study was to determine the distribution in France of the Enterobacter aerogenes prevalent clone isolated in the hospitals of the Marseille area (A. Davin-Regli, D. Monnet, P. Saux, C. Bosi, R. Charrel, A. Barthelemy, and C. Bollet, J. Clin. Microbiol. 34:1474–1480, 1996). A total of 123 E. aerogenes isolates were collected from 23 hospital laboratories and analyzed by random amplification of polymorphic DNA and enterobacterial repetitive intergenic consensus-PCR to determine their epidemiological relatedness. Molecular typing revealed that 21 of the 23 laboratories had isolated this prevalent clone harboring the plasmid encoding for extended-spectrum β-lactamase of the TEM-24 type. Most isolates were susceptible only to imipenem and gentamicin. Their dissemination seems to be clonal and was probably the result of the general use of broad-spectrum cephalosporins and quinolones. Four isolates showed an alteration of their outer membrane proteins, causing decrease of susceptibility to third-generation cephalosporins and imipenem and leading to the critical situation of having no alternative therapeutic. The large dissemination of the E. aerogenes prevalent clone probably results from its good adaptation to the antibiotics administered in France and the hospital environment, particularly in intensive care units.
PMCID: PMC85109  PMID: 10364580

Results 1-13 (13)