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Biomedical subjects

F Wallet

Publications and source records attributed to F Wallet.

At least 19 recordsLinked to original sources
PubMed2001

Assessing the risk of primary amoebic meningoencephalitis from swimming in the presence of environmental Naegleria fowleri.

Free-living Naegleria fowleri amoebae cause primary amoebic meningoencephalitis (PAM). Because of the apparent conflict between their ubiquity and the rarity of cases observed, we sought to develop a model characterizing the risk of PAM after swimming as a function of the concentration of N. fowleri. The probability of death from PAM as a function of the number of amoebae inhaled is modeled according to results obtained from animals infected with amoeba strains. The calculation of the probability of inhaling one or more amoebae while swimming is based on a double hypothesis: that the distribution of amoebae in the water follows a Poisson distribution and that the mean quantity of water inhaled while swimming is 10 ml. The risk of PAM for a given concentration of amoebae is then obtained by summing the following products: the probability of inhaling n amoebae x the probability of PAM associated with inhaling these n amoebae. We chose the lognormal model to assess the risk of PAM because it yielded the best analysis of the studentized residuals. Nonetheless, the levels of risk thereby obtained cannot be applied to humans without correction, because they are substantially greater than those indicated by available epidemiologic data. The curve was thus adjusted by a factor calculated with the least-squares method. This provides the PAM risk in humans as a function of the N. fowleri concentration in the river. For example, the risk is 8.5 x 10(-8) at a concentration of 10 N. fowleri amoebae per liter.

Amebiasis↗
PubMed2000

Peritonitis due to Staphylococcus sciuri in a patient on continuous ambulatory peritoneal dialysis.

Among the coagulase-negative staphylococci, Staphylococcus sciuri has rarely been described as the aetiology of continuous ambulatory peritoneal dialysis (CAPD) peritonitis. It has been reported in 1 case of endocarditis and has been isolated from peritoneal dialysis fluid in 2 patients. The case reported here describes CAPD peritonitis due to S. sciuri shortly after a previous episode due to S. aureus, showing the necessity to identify coagulase-negative staphylococci to find new species that cause CAPD peritonitis.

Adult↗
PubMed2000

Molecular identification of Pasteurella dagmatis peritonitis in a patient undergoing peritoneal dialysis.

Pasteurella dagmatis was identified as the etiologic agent of peritonitis in a continuous ambulatory peritoneal dialysis patient by utilizing a molecular kit in our hospital's clinical laboratory. This method would appear a useful approach to identify a species of Pasteurella not included in the existing database of commercial identification kits when discrepancies exist between phenotypic tests.

Adult↗
PubMed2000

Morphological evidence for a subpopulation selection effect by estrogen and antiestrogen treatments in the heterogeneous MCF-7 cell line.

Recently, we developed a method to quantitatively study tumour cell heterogeneity in terms of both nuclear size and estrogen receptor (ER) content by image cytometry. The method, previously used to analyse the proliferation of the breast cancer cell line MCF-7, was applied here to analyse the growth of this cell line under estradiol (E2), hydroxytamoxifen (OH-TAM), and both E2 and OH-TAM treatments. The method extracts characteristic parameters of single nuclei and features that measure the global and local organisation of the cells in their growing phase. Modifications of the heterogeneity of the cell line are emphasised through phenotypic changes and modifications of the spatial organisation of the cells. The hormone (E2) generates a very fast growth of cells with small nuclei that became ER negative in the long term. The antihormone (OH-TAM) produces a gradual selection of ER negative or poorly positive cells with large nuclei. These modifications are reversed when E2 and OH-TAM are simultaneously used. Moreover, estradiol induces a permissive context of proliferation, whereas hydroxytamoxifen acts only on some subpopulations. The combination of cell count, cytomorphology, and cell organisation revealed the magnitude of the potential of structuration of hormones or antihormones on in vitro growing cells.

Breast Neoplasms↗
PubMed1999

Opioid agonists modify breast cancer cell proliferation by blocking cells to the G2/M phase of the cycle: involvement of cytoskeletal elements.

Opioids decrease cell proliferation in different systems including breast, prostate, lung, kidney, and intestine, through an interaction with opioid as well as other membrane-receptor systems (somatostatin, cholinergic), through an unidentified mechanism. Recently, we have reported an interaction of taxol with opioid membrane sites (BBRC 235, 201-204, 1997), and an involvement of opioids to the modification of actin cytoskeleton in renal OK cells (J Cell Biochem. [19981 70:60-69), indicating a possible action of the opioid effect. In the present work, we have examined the effect of two general opioid agonists (ethylketocyclazocine and etorphine) on the cell cycle, in human breast cancer T47D cells, as well as a possible modification of the cellular cytoskeleton under their action, in order to explain the antiproliferative effect of these agents. These two opioids produce a dose-dependent and reversible decrease of the proliferation of T47D cells, with a maximum attained at 10(-8) M. The addition of 10(-8) M of either opioid produced a significant increase of the number of cells arrested in the G2/M phase. Confocal laser microscopy revealed a modification of the actin and tubulin microfilaments, with a clear redistribution at the periphery of the cell, reversed by the addition of the general opioid antagonist diprenorphine. Furthermore, differences between the two opioids were obvious, attributed to the different receptor affinity of each agent. The observed redistribution of actin and tubulin cytoskeletal elements gives therefore a possible answer of the antiproliferative action of opioids. The modification of the cytoskeleton, directly involved to cell division, might provoke a "mechanical" obstacle, which could be the reason of the antiproliferative effect of these agonists. Furthermore, the observed tubulin-opioid interaction by opioids provides a possible explanation of the arrest at the G2/M phase of T47D cells under opioid treatment. Nevertheless, although the observed interaction of opioids with cytoskeletal elements gives a plausible answer of the antiproliferative effects of the agents, this might not be the only action of these agents in cell proliferation. Other, direct or indirect, genomic actions, which which remains to be elucidated, might be taken into consideration.

Actins↗
PubMed1999

PCR detection of aminoglycoside resistance genes: a rapid molecular typing method for Acinetobacter baumannii.

Aminoglycoside resistance is common among strains of Acinetobacter baumannii responsible for nosocomial infections, and inactivation of these antibiotics by enzymatic modification is the main mechanism. Different types of aminoglycoside acetyltransferases (AAC), nucleotidyltransferases (ANT), and phosphotransferases (APH) are synthesized by clinical isolates, and several enzymes can be produced by a single strain. Using a multiplex PCR procedure carried out on bacterial thermolysates, we analyzed the aminoglycoside resistance gene content of strains belonging to eight clusters identified by pulsed-field gel electrophoresis. In a single reaction were combined three primer pairs in order to amplify the genes coding for AAC(6')-Ih, AAC(3)-I, and AAC(3)-II, three primer pairs for the genes coding for ANT(2'')-I, APH(3')-VI, and rRNA 16S as internal control, and finally two primer pairs for the genes coding for AAC(6')-Ib and APH(3')-I. According to the aminoglycoside resistance gene patterns, the strains of the eight clusters were distributed into seven classes. This simple and rapid (< 8 h) fingerprinting technique could be a useful tool for the epidemiological investigation of A. baumannii nosocomial infections.

Acetyltransferases↗
PubMed1999

Characterization of an animal model of ventilator-acquired pneumonia.

To develop an experimental model of ventilator-acquired pneumonia (VAP), we investigated whether healthy piglets could develop endogenously acquired pulmonary infection as a result of prolonged mechanical ventilation (MV). Thirty-three piglets underwent MV with anesthesia, analgesia, and paralysis produced by continuous infusion of midazolam, fentanyl, and pancuronium bromide. Ten animals received antibioprophylaxis with ceftriaxone (ATB group) and 23 received no antibiotics (control group). Eighteen control animals and 9 ceftriaxone-treated animals completed the 4-day study protocol. The presence of pneumonia on day 4 was ascertained by multiple pulmonary biopsy specimens, processed for microscopic examination and quantitative cultures. The anesthetic regimen provided satisfactory electrolyte balance and cardiovascular stability. Under these circumstances, 17 of 18 animals and 4 of 9 animals developed VAP in the control and the ATB groups, respectively. Lesions of different grades of severity were unevenly distributed through both lungs with a predominance and a higher severity in dependent lung segments. Noninfectious lesions frequently associated with VAP in humans were not observed. Pneumonia was usually polymicrobial with a predominance of Gram-negative organisms. Most of the causative organisms originated from the oropharynx. Histologic lesions and lung bacterial concentrations were less in the ATB group than in control animals. We then investigated the effects of intrabronchial challenge with bacterial pathogens in the absence of MV. Intrabronchial bacterial inoculation resulted in the development of pneumonia that spontaneously resolved even when using very highly titrated inocula. Therefore, MV seems to be the main predisposing factor in the development of pneumonia in this model. This model that resembles human VAP in its histologic, bacteriologic, and pathogenic aspects may be useful to further study pathogenesis, diagnosis, prevention, and therapy of VAP.

Animals↗
PubMed1998

Influence of pulmonary bacteriology and histology on the yield of diagnostic procedures in ventilator-acquired pneumonia.

We investigated the influence of pulmonary bacteriology and histology on the yield of diagnostic procedures in a clinically relevant model of ventilator-acquired pneumonia (VAP). Twenty-seven piglets entered a 4-d protocol of ventilatory support under general anesthesia. Endotracheal aspirates (EA), protected specimen brush (PSB), and bronchoalveolar lavage (BAL) were obtained on Day 4. PSB and BAL were performed under bronchoscopic guidance in dependent and nondependent lung segments. Immediately thereafter sternotomy allowed bilateral lung biopsies including the segments studied by bronchoscopic techniques. All respiratory specimens were then processed for microscopic examination and quantitative cultures (QC). In this model where many of the confounding factors often present in human studies were absent, we found that (1) although the local bacterial burden tended to correlate with the presence and the severity of histologic lesions, no definite bacteriologic cutoff could differentiate the histologic presence or absence of pneumonia; (2) histologic lesions of pneumonia and parenchymal bacterial burden were unevenly distributed through the lungs; (3) this heterogeneity in bacterial distribution also held true for single bacterial species; (4) using discriminative values of >= 10(3) cfu/ml, >= 10(4) cfu/ml, and >= 10(5) cfu/ml to define positive PSB, BAL, and EA cultures, respectively, these techniques identified the histologic presence of pneumonia with a sensitivity of 69%, 78%, and 100%, respectively; (5) the specificity of these techniques in recognizing VAP was less than 50%; (6) with these discriminative values, less than 50% of PSB and BAL specimens correctly identified the causative organisms, whereas 94% of EA specimens correctly established the microbiologic diagnosis of pneumonia. We believe that the peculiar histologic and bacteriologic features of VAP may account for the difficulties of PSB and BAL, which combine QC with the use of discriminative thresholds, to reliably recognize pneumonia and to identify the causative organisms. For clinical practice, no technique confidently helps in recognizing pneumonia in mechanically ventilated patients. With regard to bacterial diagnosis, use of quantitative cultures of EA seems to be the best technique to identify the causative organisms in patients suffering VAP.

Animals↗
PubMed1997

Multifactorial comparative study of spatial point pattern analysis methods.

A way of studying cooperative behaviour of biological entities (proteins, cells, etc.) is by using topographical analysis: the quantification of the spatial patterns formed by the entities considered as points. Five methods of topographical analysis were compared in terms of discriminant power, stability of parameters, methodological bias and algorithms. We tested five methods (nearest neighbour distribution, radial distribution, Voronoï paving, quadrat count, minimal spanning tree graph) which generated nine parameters on four simulated models (random point process, hardcore model and two cluster models) and on experimental cellular models. The method which offers the best discrimination power and stability seems to be the minimal spanning tree graph edge length distribution.

Animals↗
PubMed1997

Effect of vancomycin and teicoplanin alone or in combination with fusidic acid or amikacin against methicillin-resistant staphylococci.

The action of two glycopeptides (vancomycin and teicoplanin) alone or in combination with amikacin or fusidic acid has been studied against 10 non-repetitive strains of methicillin-resistant Staphylococcus. The plotted killing curves show that the combination of vancomycin or teicoplanin plus fusidic acid always exhibited an antagonist effect at 24 h for the 10 strains. The combination vancomycin or teicoplanin plus amikacin shows the same effect at 24 h as vancomycin or teicoplanin alone. Thus, the combination glycopeptide plus amikacin does not alter the activity of the glycopeptide but does increase the spectrum of activity of the combination versus Gram-negative nosocomial bacteria (Pseudomonas aeruginosa, Acinetobacter sp). The vancomycin or teicoplanin plus fusidic acid combination may be responsible for bacteriological failure against methicillin-resistant Staphylococcus.

Amikacin↗
PubMed1997

Rothia dentocariosa: two new cases of pneumonia revealing lung cancer.

Pneumonia due to Rothia dentocariosa is extremely rare: only 1 case of pneumonia due to this pathogen has been reported in an immunocompromised patient with acute myelocytic leukemia. In this report, 2 new cases of Rothia dentocariosa pneumonia are described in 2 patients with lung cancer. This opportunistic pulmonary agent, belonging to the oro-pharyngeal flora, is also known to cause endocarditis in patients with underlying cardiac pathology.

Actinomycetales Infections↗
PubMed1997

[Fibroscopic bronchoscopy in intensive care].

The field of application for fibreoptic bronchoscopy (FB) in the intensive care unit has been extended since the generalised introduction of fibroscopes of 4.9 mm in diameter (previously called paediatric fibroscopes). Paediatric and neonatal intensive care units have benefited from the availability in the market of these small endoscopes for 3.5 and 2.2 mm. The protected brush and alveolar lavage (LBA) enables a specific diagnosis to be made in bacterial pneumonia acquired during ventilation. The sensitivity of these techniques however is insufficient to be able to recommend their use as routine. Inversely, the FB with LBA remains a fundamental feature in the diagnosis of opportunistic infections in pneumonia. For the treatment of atelectasis, FB is overall not superior to physiotherapy. Aspiration with a fibroscope can however be recommended straight away in cases of alteration in blood gasses if cough is ineffective or if the atelectasis complicates endobronchial bleeding. The FB enables problems with difficult intubation to be resolved or for the positioning of probes. The conditions under which this is performed are more delicate than in routine anaesthesia (in cases of urgency, hypoxia). In the case of respiratory burns, tracheobronchial fracture and post intubation stenosis, FB enables both the diagnosis to be established and the level at which the lesion occurs. In paediatric intensive care, a fibroscope of 3.5 mm is used for performing LBA (opportunistic pneumonias), difficult intubation (facial dysmorphia), endoscopic diagnoses, in particular where there is a suspicion of an endobronchial foreign body, the assessment of unexplained dyspnoea (tracheal stenosis by vascular ring) and obstructive lesions. In neonatal intensive care, a fibroscope of 2.2 mm is used for difficult intubation and the localisation of lesions induced by ventilation.

Adult↗
PubMed1997

[Contribution of the topographical analysis to quantitative microscopy in cultured cell systems: application to the evaluation of hormone therapy].

Quantitative microscopy by image analysis allows not only to measure various parameters on each cell but also to consider the global population as a whole. In the hypothesis that cell position is reflecting the relational and dynamical structure of the system, spatial arrangement analysis may help to show up intercellular communication (interactions and control systems via contact or diffusible factors). We describe a topographical analysis method used to study these neighbour relationships, and thus the sociological behaviour of the cells. It is applied to the study of the effect of estrogenic and antiestrogenic treatments on a breast cancer cell line (MCF-7). It shows up that estrogens increase proliferation and induce an unusual topographical behaviour, notably in cell cycle phases: cells in S phases are very randomly distributed. It points out the role of estrogens on the cells neighbour relationships inducing the way to a permissive proliferation context. This effect is reversed by antiestrogenic treatment after a few days. Antiestrogenic treatment alone increases the proliferation constraint.

Breast Neoplasms↗
PubMed1996

Toward a new method to in situ study of apoptosis and its relations with cell cycle.

Apoptosis or programmed cell death plays a key role in many biological processes particularly in oncology. The detection of apoptotic cells is crucial for the study of the phenomenon itself and its relation with the proliferative cell cycle. A new method to detect apoptosis in situ in Feulgen stained cells was developed, based on multiparametric analysis (factorial and decisional analysis), using 15 densitometric and textural parameters measured on a SAMBA 200 cell image processor. Six reference files corresponding to G1, S, and G2 phases and to apoptotic cells derived from these cell cycle phases were constructed. The projection of these files in the factorial principal plane formed distinct clusters. Using the decisional discriminant analysis, it was possible to ascertain the state (apoptosis or proliferative) and the phase for each cell of a population. The correct classification rate of this analysis was 0.9962. Determining the cell cycle phase from which each apoptotic cell comes, we are able to study the relation between apoptosis and the proliferative cell cycle. Moreover, the detection in situ allows us to study cell-cell interactions.

Apoptosis↗
PubMed1996

Choice of a routine method for detecting methicillin-resistance in staphylococci.

Four methods were compared for their abilities to detect methicillin-resistance of Staphylococcus strains using mecA gene PCR analysis in 6 h as the gold standard. 57 Staphylococcus aureus and 100 coagulase negative staphylococci (CNS) were evaluated by the oxacillin disc diffusion method (Kirby-Bauer), the automated API (ATB-plus) system (bioMérieux, La Balme les Grottes, France) in 24 h, the rapid BBL Crystal MRSA ID system (Becton Dickinson, Cockeysville, Md.), the oxillin MICs using the NCCLS agar dilution method in 24 h, and the mecA gene PCR analysis. For S. aureus, the correlation was excellent between the BBL Crystal MRSA ID system and mecA gene PCR analysis (positive predictive value = 100%; negative predictive value = 97%) and oxacillin MIC (positive predictive value = 96%; negative predictive value = 96%). The correlation between BBL Crystal MRSA ID and mecA gene PCR was not reliable for CNS (negative predictive value = 68%). For CNS, the slower routine susceptibility methods to identify intrinsic methicillin-resistance were better: API ATB Staph has a positive predictive value = 94% and a negative predictive value = 82%, and the disc diffusion test has a positive predictive value = 95% and a negative predictive value = 74%. However, BBL Crystal MRSA ID was as reliable as some of the other methods tested for CNS after 6 h incubation when the inoculum was increased: positive predictive value = 94% and a negative predictive value = 77%. These results emphasize that genotypic detection of methicillin-resistance will undoubtedly become important to detect rapidly methicillin-resistance, especially for CNS.

Bacterial Proteins↗
PubMed1996

Relationship between microbiologic and histologic features in bacterial pneumonia.

To investigate the relationship between the lung damage resulting from pneumonia and the local bacterial burden, we conducted a study comparing histologic and bacteriologic findings in pigs infected with bacterial pneumonia while free of antibiotic therapy and previous or concomitant lung disease. Seventy-eight lung specimens were obtained from 17 animals. The main findings are the following: (1) histologic lesions of pneumonia as well as parenchymal bacterial burden were unevenly distributed within the lungs and even within the lung segments; (2) specimens showing histologic evidence of pneumonia had significantly higher bacterial counts than specimens with bronchial infection and specimens with neither bronchial nor lung infection; (3) there was no significant difference in bacterial counts between lesions defined as pneumonia, confluent pneumonia and abscessed pneumonia; (4) we could not define a clearcut threshold for quantitative cultures to discriminate the presence or absence of pneumonia. This study providing experimental insights into the relationship between microbiologic and histologic features in bacterial pneumonia confirms previous findings in humans. Although, for investigational purpose, lung cultures can be helpful in determining the bacterial etiology of pneumonia, these data do not support the use of quantitative cultures for establishing a definite diagnosis of pneumonia.

Animals↗
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↗