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Biomedical subjects

R Bonnet

Publications and source records attributed to R Bonnet.

At least 19 recordsLinked to original sources
PubMed2006

Pseudomonas aeruginosa and Pseudomonas putida outbreak associated with contaminated water outlets in an oncohaematology paediatric unit.

This paper describes an outbreak of Pseudomonas aeruginosa and Pseudomonas putida that occurred in an oncohaematology paediatric unit between January and April 2005. Eight children had nosocomial infections due to P. aeruginosa (N=5) or P. putida (N=3), which were recovered from central venous catheter blood cultures (N=4), the catheter exit site alone (N=2), or the catheter exit site and the catheter tip (N=2). Subsequent investigation showed that contaminated water outlets represented the possible source of spread. Studies of nursing and environmental cleaning practices revealed two modes of catheter contamination. A reduction in the size of the catheter dressing at the exit site gave less protective cover during showers, and a detergent-disinfectant diluted with tap water had contaminated perfusion bottles. Repetitive intergenic consensus polymerase chain reaction indicated two discrete patterns for P. aeruginosa and one for P. putida. The water network was chlorinated, and disposable seven-day filters were fitted on all taps and showers. Due to the deleterious effects of chlorination on the water network and the cost of the weekly filter change, a water loop producing microbiologically controlled water was installed. In addition, the concentration of the detergent-disinfectant was increased and refillable sprayers were replaced with ready-to-use detergent-disinfectant solution for high-risk areas. Following these measures, no Pseudomonas spp. have since been isolated in clinical or environmental samples from the ward.

Adolescent↗
PubMed2006

Outbreak of colonization and infection with vancomycin-resistant Enterococcus faecium in a French university hospital.

An outbreak of infection with vancomycin-resistant Enterococcus faecium occurred at Hotel-Dieu Hospital (Clermont-Ferrand, France). A case-control study was performed in the infectious diseases and hematology units of the hospital. Urinary catheter use (odds ratio [OR], 12 [95% confidence interval {CI}, 1.5-90]; P<.02), prior exposure to a third-generation cephalosporin (OR, 22 [95% CI, 3-152]; P=.002), and prior exposure to antianaerobials (OR, 11 [95% CI, 1.5-88]; P<.02) were independently predictive of vancomycin-resistant Enterococcus faecium carriage.

Disease Outbreaks↗
PubMed2006

2,9-Dimethyl-beta-carbolinium, a neurotoxin occurring in human brain, is a potent inducer of apoptosis as 1-methyl-4-phenylpyridinium.

The causes of neurodegeneration are not well understood. However, the role of environmental and endogenous toxins is receiving much attention. In this study, we compared the synthetic neurotoxin 1-methyl-4-phenyl-pyridinium with beta-carbolines occurring in human brain. Methylation of both nitrogens is necessary to convert a beta-carboline into a potent inhibitor of mitochondrial complex I. The respective beta-carboline, 2,9-dimethyl-beta-carbolinium ion is neurotoxic in rats. To investigate the underlying mechanisms, we incubated mouse neuroblastoma 2A cells with 2,9-dimethyl-beta-carbolinium ion, and compared the findings with effects of norharman, the precursor beta-carboline of methylated derivatives, and with 1-methyl-4-phenyl-pyridinium. 2,9-Dimethyl-beta-carbolinium ion caused a significant increase of reactive oxygen species (higher efficiency than 1-methyl-4-phenyl-pyridinium) and of mitochondrial membrane potential within the first minutes. After 60 min, the membrane potential dissipated. Concomitantly, the levels of glutathione increased in 2,9-dimethyl-beta-carbolinium ion but not in 1-methyl-4-phenyl-pyridinium treated cells. After 24 h effector caspases 3 and 7 were activated and the number of apoptotic cells increased as revealed by fluorescence-activated cell sorting cytometry. When incubated longer (48 h), cells underwent late apoptosis/secondary necrosis as shown by fluorescence-activated cell sorting analysis and confirmed qualitatively by an electron microscopy study. The effects of 2,9-dimethyl-beta-carbolinium ion on apoptotic changes were similar to those induced by 1-methyl-4-phenyl-pyridinium(,) while norharman showed only a weak potency at the very high doses. To investigate whether 2,9-dimethyl-beta-carbolinium ion is neurotoxic under in vivo conditions and whether only dopaminergic neurones are affected we conducted a dose-response study. Three weeks after injection of 2,9-dimethyl-beta-carbolinium ion in the substantia nigra we found a dose-dependent decrease of dopamine and its metabolites in the striatum of rats. The levels of 5-hydroxytryptamine were diminished although the decrease was less. The levels of noradrenaline increased after some doses. The findings strongly suggest an important role of endogenous beta-carbolines in neurodegeneration with apoptosis as the predominant mechanism.

1-Methyl-4-phenylpyridinium↗
PubMed2006

Occurrence of qnrA-positive clinical isolates in French teaching hospitals during 2002-2005.

Bacteria harbouring the novel qnrA plasmid-mediated mechanism of quinolone resistance have been described in different countries, but the frequency of their occurrence has not been investigated. In total, 1,468 clinical isolates of Enterobacteriaceae with quinolone resistance or extended-spectrum beta-lactamase (ESBL) phenotypes were collected from eight teaching hospitals in France during 2002-2005 and screened for qnrA. Overall, 28 isolates (22 Enterobacter cloacae, three Klebsiella pneumoniae, one Citrobacter freundii, one Klebsiella oxytoca and one Proteus mirabilis) were positive for qnrA, representing 1.9% of all isolates, 3.3% of ESBL-producing isolates (22% of the E. cloacae isolates) and 0% of non-ESBL-producing isolates. The prevalence of qnrA among consecutive ESBL-producing isolates in 2004 from the eight hospitals was 2.8% (18/639). Of the qnrA-positive isolates, 100% were intermediately-resistant or resistant to nalidixic acid, and 75% to ciprofloxacin. Twenty-one of the 22 qnrA-positive E. cloacae isolates were obtained from two hospitals in the Paris area, and molecular typing and plasmid content analysis showed clonal relationships for five, three and two isolates, respectively. The qnrA genetic environment was similar to that of the In36 integron. The remaining two isolates had qnrA variants (30 and 29 nucleotide differences, respectively, compared with the original sequence) and an unknown genetic environment. The ESBL gene associated with qnrA was bla(SHV-12) in most of the isolates, but bla(PER-1) and bla(SHV-2a) were found in two isolates. In France, it appears that qnrA-positive isolates are predominantly E. cloacae isolates producing SHV-12, and may be associated with the dissemination of an In36-like integron.

Bacterial Proteins↗
PubMed2006

Prediction of the evolution of ceftazidime resistance in extended-spectrum beta-lactamase CTX-M-9.

A random mutagenesis technique was used to predict the evolutionary potential of beta-lactamase CTX-M-9 toward the acquisition of improved catalytic activity against ceftazidime. Thirty CTX-M mutants were obtained during three rounds of mutagenesis. These mutants conferred 1- to 128-fold-higher MICs of ceftazidime than the parental enzyme CTX-M-9. The CTX-M mutants contained one to six amino acid substitutions. Mutants harbored the substitutions Asp240Gly and Pro167Ser, which were previously observed in clinical CTX-M enzymes. Additional substitutions, notably Arg164His, Asp179Gly, and Arg276Ser, were observed near the active site. The kinetic constants of the three most active mutants revealed two distinct ways of improving catalytic efficiency against ceftazidime. One enzyme had a 17-fold-higher k(cat) value than CTX-M-9 against ceftazidime. The other two had 75- to 300-fold-lower Km values than CTX-M-9 against ceftazidime. The current emergence of CTX-M beta-lactamases with improved activity against ceftazidime may therefore be the beginning of an evolutionary process which might subsequently generate a great diversity of CTX-M-type ceftazidimases.

Ceftazidime↗
PubMed2005

[VCA agar (bioMérieux) for selective isolation of vancomycin-resistant Enterococci (VRE) from fecal specimens].

Screening for Vancomycin Resistant Enterococci (VRE) is recommended for preventing nosocomial infections with VRE. The aim of this study was to assess the performance of VCA3 agar (bioMérieux) in VRE isolation from fecal specimens. 220 specimens were cultured on VCA3 agar, which contains vancomycin and in parallel, on CAP agar (Oxoid), which is vancomycin-free. 36 vancomycin resistant enterococci were isolated: 24 isolates of Enterococcus faecium expressed a high-level resistance to vancomycin and 12 isolates of E. gallinarum/casseliflavus exhibited resistance at low-level. The sensitivity of VCA3 appeared greater than that of CAP for VRE isolation: 92% (22/24) vs 79% (19/24) for E. faecium (NS, P>0.05) ; 83% (10/12) vs 50% (6/12) for E. gallinarum/casselliflavus (NS, P>0.05). As expected, initial cultures of multiple gram positive organisms were far more frequent on CAP agar than on VCA3 agar. The isolation rate of vancomycin susceptible gram positive strains was impressively lower on VCA3 medium than on CAP medium. VCA3 agar avoided therefore additional subcultures, useless identification and susceptibility tests. In conclusion, VCA3 medium could be useful for the direct, rapid and selective isolation of VRE from fecal specimens.

Cross Infection↗
PubMed2005

[Correlation of histologic results with PET findings for tumor regression and survival in locally advanced non-small cell lung cancer after neoadjuvant treatment].

UNLABELLED: CT cannot provide useful information in a timely manner after neoadjuvant treatment. To evaluate the role of (18)F FDG PET after neoadjuvant chemoradiation for early therapy response and its effect on survival as compared to histopathologic tumor response, findings in 32 patients were analyzed prospectively in an ongoing multicenter trial (LUCAS-MD). INCLUSION CRITERIA: histologically confirmed NSCLC stage IIIA/IIIB. Neoadjuvant treatment: 2-3 cycles with paclitaxel/carboplatin and a block of chemoradiation followed by surgery. Pretherapeutic staging: PET scan in addition to a spiral CT and/or MRI. Second PET scan after completion of neoadjuvant therapy prior to surgery. Documentation of lymph node involvement. Assessment of SUV and the metabolic tumor index for primary tumor and metastatic lymph nodes. Image fusion of PET with CT data followed by molecular radiation treatment planning. Evaluation of histologic regression grade and correlation with PET for primary tumor and each lymph node location. All patients (10/32) with complete response in lymph node metastases detected by PET prior to surgery, had no vital tumor cells (i.e. histologic regression grade/RG III, sensitivity 100%). In primary tumors showing complete response, the RG was IIb or III, in one patient IIa (false negative in PET). False positive findings in PET are due to inflammation (5 patients, histologically confirmed). Univariate analyses: actuarial tumor-specific survival for complete metabolic remission vs. incomplete remission after 24 months: 76 vs. 20% (p=0,0079); for RG III/IIb vs. RG IIa/I after 24 months: 63 vs. 36% (p=0,0123).(18)F FDG PET precedes CT in measuring the tumor response and may predict (long term) therapeutic outcome in stage III NSCLC. Histologic regression grade correlates well with metabolic remission as detected by PET.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Unexpected enzyme TEM-126: role of mutation Asp179Glu.

The clinical isolate Escherichia coli CF884 exhibited low-level resistance to ceftazidime (4 mug/ml) by a positive double-disk synergy test and apparent susceptibility to cefuroxime, cefotaxime, cefepime, cefpirome, and aztreonam. The enzyme implicated in this phenotype was a novel 180-kb plasmid-encoded TEM-type extended-spectrum beta-lactamase designated TEM-126 which harbors the mutations Asp179Glu and Met182Thr. TEM-126 exhibited significant hydrolytic activity (k(cat), 2 s(-1)) and a K(m) value of 82 muM against ceftazidime. Molecular dynamics simulations suggested that the substitution Asp179Glu induces subtle conformational changes to the omega loop which may favor the insertion of ceftazidime in the binding site and the correct positioning of the crucial residue Glu166. Overall, these results highlight the remarkable plasticity of TEM enzymes, which can expand their activity against ceftazidime by the addition of one carbon atom in the side chain of residue 179.

Amino Acid Sequence↗
PubMed2005

TEM-109 (CMT-5), a natural complex mutant of TEM-1 beta-lactamase combining the amino acid substitutions of TEM-6 and TEM-33 (IRT-5).

Escherichia coli CF349 exhibited a complex beta-lactam resistance phenotype, including resistance to amoxicillin and ticarcillin alone and in combination with clavulanate and to some extended-spectrum cephalosporins. The double-disk synergy test was positive. CF349 harbored an 85-kb conjugative plasmid which encoded a beta-lactamase of pI 5.9. The corresponding bla gene was identified by PCR and sequencing as a bla(TEM) gene. The deduced protein sequence revealed a new complex mutant of TEM-1 beta-lactamase designated TEM-109 (CMT-5). TEM-109 contained both the substitutions Glu104Lys and Arg164His of the expanded-spectrum beta-lactamase (ESBL) TEM-6 and Met69Leu of the inhibitor-resistant TEM-33 (IRT-5). TEM-109 exhibited hydrolytic activity against ceftazidime similar to that of TEM-6 (k(cat), 56 s(-1) and 105 s(-1), respectively; K(m) values, 226 and 247 microM, respectively). The 50% inhibitory concentrations of clavulanate and tazobactam (0.13 microM and 0.27 microM, respectively) were 5- to 10-fold higher for TEM-109 than for TEM-6 (0.01 and 0.06 microM, respectively) but were almost 10-fold lower than those for TEM-33. The characterization of this novel CMT, which exhibits a low level of resistance to inhibitors, highlights the emergence of this new ESBL type.

Amino Acid Substitution↗
PubMed2004

Frequency and diversity of Class A extended-spectrum beta-lactamases in hospitals of the Auvergne, France: a 2 year prospective study.

OBJECTIVES: To evaluate the frequency and diversity of extended-spectrum beta-lactamases (ESBLs) produced by Enterobacteriaceae and Pseudomonas aeruginosa in one French region. METHODS: During 2001-2002, all the non-duplicate isolates of P. aeruginosa resistant to ceftazidime and of Enterobacteriaceae intermediate or resistant to ceftazidime and/or cefotaxime and/or aminoglycosides with an AAC(6') I phenotype were collected in nine hospitals of the area. ESBL isoelectric points were determined, bla genes were amplified and sequenced and epidemic isolates were genotyped with ERIC2-PCR. RESULTS: ESBLs were observed in 297 Enterobacteriaceae (0.8%). The most frequent were TEM-3 like (n=152; 51.2%) and TEM-24 (n=115; 38.7%). Four new enzymes were observed, TEM-112 (pI 5.4), TEM-113 (pI 6.3), TEM-114 (pI 5.9) and TEM-126 (pI 5.4). Other TEMs were TEM-8, TEM-12, TEM-16, TEM-19, TEM-20, TEM-21, TEM-29 and TEM-71. The other ESBLs were SHV-4, SHV-5 and SHV-12, CTX-M-1, CTX-M-3, CTX-M-14 and CTX-M-15. In 37 P. aeruginosa (0.7%) only one ESBL was observed, PER-1. Five epidemic strains were detected, Serratia marcescens TEM-3 and four observed in several hospitals, Enterobacter aerogenes TEM-24, Citrobacter koseri TEM-3, Proteus mirabilis TEM-3 and P. aeruginosa PER-1. CONCLUSION: ESBL frequency was lower than in 1998, and CTX-M-type frequency higher (2.1% of ESBLs in 2001, 4.9% in 2002). This long-term survey detected new sporadic enzymes (TEM-112, TEM-113, TEM-114 and TEM-126) and interhospital epidemic strains while avoiding any overestimation of ESBL frequency that may otherwise have occurred because of acute epidemics.

Amino Acid Substitution↗
PubMed2004

The strong inhibition of triosephosphate isomerase by the natural beta-carbolines may explain their neurotoxic actions.

The natural beta-carbolines (BC) closely resemble the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in structure. The N-methylated beta-carbolinium ions (BC+) are potent inhibitors of mitochondrial respiration and are nigrostriatal neurotoxins. Utilizing [3H]BC, we have identified several proteins to which BC binds with high affinity (e.g. the chaperone member glucose regulated protein 78, the enzyme carboxylesterase, the cytochrome P450 2E1, the enzyme monoamine oxidase B and a small G-protein of the Rho subfamily). In the present study we isolated a protein from bovine brain to which [3H]BC binds with high affinity and identified it being the enzyme triosephosphate isomerase (TPI; EC 5.3.1.1.). 2,9-Dimethyl-BC+ was the most potent inhibitor of TPI, clearly more potent than the known inhibitors. TPI deficiency is a rare disorder in humans characterized by a severe progressive extrapyramidal course. Thus, TPI inhibition could contribute to neurodegeneration observed after injection of BCs into substantia nigra. Furthermore, the findings fit into the hypothesis of BCs as endogenous toxins responsible for neurodegeneration.

Animals↗
PubMed2004

[Respiratory therapist: introduction of a new profession].

Respiratory therapists are healthcare professionals taking care of patients with pulmonary disorders. They are an allied health specialty, practicing under medical direction. The professionalism of nurses and therapists must grow up to act successfully in new fields of medicine, where evidence-based independent action is necessary. Specialized therapists can help us coordinate separated processes (diagnoses, therapy and nursing). The profession "Respiratory Therapist" was created in the United States 50 years ago. We intend to introduce this profession also in Germany. We follow many other countries who have already taken this step. We hope that we can reach yet a higher quality of patient care.

Evidence-Based Medicine↗
PubMed2003

Effect of D240G substitution in a novel ESBL CTX-M-27.

Escherichia coli clinical strain Gre-1 collected in 2000 from a French hospital harboured a novel CTX-M-encoding gene, designated blaCTX-M-27. CTX-M-27 differed from CTX-M-14 only by the substitution D240G and was the third CTX-M enzyme harbouring this mutation after CTX-M-15 and CTX-M-16. The Gly-240-harbouring enzyme CTX-M-27 conferred to E. coli higher MICs of ceftazidime (MIC, 8 versus 1 mg/L) than did the Asp-240-harbouring CTX-M-14 enzyme. Comparison of CTX-M-14 and CTX-M-27 showed that residue Gly-240 decreased Km for ceftazidime (205 versus 940 microM), but decreased hydrolytic activity against good substrates, such as cefotaxime (kcat, 113 versus 415 s-1), probably owing to the alteration of beta3 strand positioning during the catalytic process.

Amino Acid Substitution↗
PubMed2003

Effects of Ser130Gly and Asp240Lys substitutions in extended-spectrum beta-lactamase CTX-M-9.

In CTX-M-9 extended-spectrum beta-lactamases (ESBLs), an S130G mutation induced a 40- to 650-fold increase in 50% inhibitory concentrations but decreased hydrolytic activity against cefotaxime. A D240K mutation did not modify enzymatic efficiency against ceftazidime. Residue K240 could interact with Q270 and therefore not with ceftazidime, in contrast with what was observed with certain TEM/SHV-type ESBLs.

Amino Acid Substitution↗
PubMed2002

CTX-M-1, CTX-M-3, and CTX-M-14 beta-lactamases from Enterobacteriaceae isolated in France.

Six clinical CTX-M-producing isolates of the family Enterobacteriaceae were detected between 1999 and 2000 in different French hospitals. Two strains produced CTX-M-1 and CTX-M-3 and four strains produced CTX-M-14, a mutant Ala-231-->Val of CTX-M-9. A putative transposable element, ISEcp-1, was located 43 bp upstream of all the bla(CTX-M) genes. Two CTX-M-14-encoding plasmids exhibited similar restriction patterns. The CTX-M-1- and CTX-M-3-encoding plasmids were related to the CTX-M-1- and CTX-M-3-encoding plasmids previously reported in 1990 in France and in 1998 in Poland, respectively.

DNA Transposable Elements↗
PubMed2002

TEM derivative-producing Enterobacter aerogenes strains: dissemination of a prevalent clone.

TEM-24 (CAZ-6) extended-spectrum beta-lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in Klebsiella pneumoniae (bla(TEM-24)) and Enterobacter aerogenes (bla(TEM-24b)), and since 1994, a TEM-24-producing E. aerogenes clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing E. aerogenes strains, 84 E. aerogenes strains (non-TEM/SHV-producing strains, TEM-1- or -2-producing strains, and different ESBL-producing strains), isolated from 1988 to 1999 in Clermont-Ferrand (n = 59) and in 11 other French hospitals in 1998 (n = 25), were studied. A clonal strain was found for TEM-24- but also for TEM-3- and TEM-1- or 2-producing isolates. This study shows that there is a clonal strain dependent on acquisition of the TEM-type enzyme (TEM-24 and other TEM types).

Bacterial Proteins↗