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Biomedical subjects

M Maurin

Publications and source records attributed to M Maurin.

47 records · Page 3Linked to original sources
PubMed1994

[A new bacterium: Rochalimaea].

Originally limited to trench fever, infections due to Rochalimaea now comprise manifestations particular to patients with human immunodeficiency virus (bacillary angiomatosis and hepatic peliosis), but also manifestations as diverse as isolated fever, septicaemia, endocarditis, lymphocytic meningitis, or central neurological disorders, in immunodepressed or immunocompetent subjects. The involvement of Rochalimaea in cat-scratch fever remains debated. Microbiological analysis used for diagnosis has been modified to allow isolation of these new bacteria, whose culture is slow and difficult, in the course of the above-cited clinical manifestations, which should further extend the range of Rochalimaea infections.

Alphaproteobacteria↗
PubMed1994

Brain abscess due to Gordona terrae in an immunocompromised child: case report and review of infections caused by G. terrae.

A brain abscess complicated antineoplastic chemotherapy for a primary cerebral rhabdoid tumor in an immunocompromised boy. Culture of purulent exudate obtained by surgical puncture of an intracranial hematoma yielded a gram-positive microorganism initially identified as a Rhodococcus species by conventional biochemical analysis; however, the isolate was subsequently identified as Gordona terrae by ribosomal DNA analysis. To our knowledge, this is the third case of human infection caused by G. terrae and the first case of a brain abscess due to this organism. As this case demonstrates, this species may cause opportunistic invasive infection in severely immunocompromised patients. The identity of clinical isolates believed to be G. terrae should be confirmed by molecular methods until better species-specific phenotypic markers become available.

Actinomycetales↗
PubMed1994

Phagolysosomal alkalinization and intracellular killing of Staphylococcus aureus by amikacin.

The aminoglycosides are ineffective against intracellular Staphylococcus aureus, which resides within lysosomes, despite a strong extracellular bactericidal activity. Since they are slowly concentrated within lysosomes it was hypothesized that acidity within these cell compartments might impair antibiotic activity. The bactericidal activity of amikacin alone and combined with lysosomotropic alkalinizing agents (LAA), which can alkalinize acidic cell compartments, was evaluated. Before antibiotic challenge, some cells were preincubated with amikacin for 3 days to allow intracellular accumulation of drug. No intracellular killing activity was shown when non-preincubated cells were used. Conversely, with preincubated cells, S. aureus was killed within 4 h when LAA were incorporated into the incubation media but not with amikacin alone. Enhanced antimicrobial activity correlated with increase in lysosomal pH. Intracellular accumulation of amikacin was not changed by LAA. These results provide evidence that acidic pH within lysosomes impairs amikacin in killing S. aureus.

Amikacin↗
PubMed1994

Isolation and characterization by immunofluorescence, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western blot, restriction fragment length polymorphism-PCR, 16S rRNA gene sequencing, and pulsed-field gel electrophoresis of Rochalimaea quintana from a patient with bacillary angiomatosis.

Rochalimaea quintana was isolated from the blood of a French human immunodeficiency virus-infected patient with bacillary angiomatosis. The isolate showed the typical growth characteristics of Rochalimaea species and was inert when typical biochemical testing was used. The purpose of the present work was to characterize and compare this new isolate with reference strains of R. quintana, Rochalimaea vinsonii, and Rochalimaea henselae by using immunofluorescence, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot (immunoblot), restriction fragment length polymorphism-PCR of the citrate synthase gene, 16S rRNA gene sequencing, and pulsed-field gel electrophoresis. SDS-PAGE, Western blot, restriction fragment length polymorphism-PCR with TaqI enzyme, and 16S rRNA gene sequencing could differentiate the three Rochalimaea species and allowed characterization of the French isolate as R. quintana. However, identification of the Rochalimaea isolate to the species level was more easily obtained by immunofluorescence with specific murine antisera. Pulsed-field gel electrophoresis allowed differentiation of the French R. quintana isolate from R. quintana Fuller and may serve as an epidemiological tool.

AIDS-Related Opportunistic Infections↗
PubMed1993

Antimicrobial susceptibility of Rochalimaea quintana, Rochalimaea vinsonii, and the newly recognized Rochalimaea henselae.

The susceptibility of an isolate of Rochalimaea quintana, Rochalimaea vinsonii and the newly recognized Rochalimaea henselae to antimicrobial agents was determined by dilution in Mueller-Hinton agar supplemented with 5% sheep blood. Two inocula of 10(2) and 10(4) cfu were used and tests were read after incubation at 5 and 7 days at 37 degrees C in an atmosphere enriched to 5% carbon dioxide. Each isolate was susceptible to amoxycillin, third-generation cephalosporins, tetracyclines, macrolides and rifampicin, with complete inhibition of bacterial growth at concentrations lower than 0.125 mg/L. Co-trimoxazole and aminoglycosides were also active. Conversely, MICs for oxacillin, cephalothin, clindamycin, chloramphenicol and the fluoroquinolones were around the maximum concentrations achievable in serum. Vanocomycin showed moderate activity with MICs of < or = 4 mg/L. These results are consistent with clinical experience in antibiotic treatment of R. henselae infections since failures were reported with first-generation cephalosporins and the isoxazolyl penicillins. However, the frequent relapses that are observed with other beta-lactams, tetracyclines or macrolides do not accord with the in-vitro susceptibility of Rochalimaea spp. Poor bactericidal activity as well as the intracellular growth of the bacteria within infected hosts, may explain such discrepancies.

Anti-Bacterial Agents↗
PubMed1993

In vitro susceptibilities of spotted fever group rickettsiae and Coxiella burnetti to clarithromycin.

The in vitro bacteriostatic activity of clarithromycin, a new macrolide derivative, against Rickettsia rickettsii, Rickettsia conorii, and "Rickettsia israeli" was determined by the plaque assay and the dye uptake assay. Both bacteriostatic and bactericidal activities of clarithromycin against the Nine Mile, Q212, Priscilla, and ME9 strains of Coxiella burnetti were evaluated by using three cell culture systems. Clarithromycin showed improved antibacterial activity compared with that of erythromycin. A bacteriostatic activity was obtained at concentrations below the reported maximum concentration of clarithromycin in human serum (about 4 micrograms/ml) for all tested rickettsiae. MICs ranged from 1 to 2 micrograms/ml for the three Rickettsia species and from 1 to 4 micrograms/ml for the C. burnetti strains. No bactericidal activity against C. burnetti was obtained when clarithromycin was used at 4 micrograms/ml.

Animals↗
PubMed1993

Antibiotic susceptibilities of Afipia felis in axenic medium and in cells.

Afipia felis, one of the putative agents of cat scratch disease (CSD), is a facultative intracellular bacterium. Although CSD is considered not to be susceptible to antibiotic therapy, sporadic case reports indicated that aminoglycosides may be effective. We determined the in vitro antibiotic susceptibilities of three A. felis strains in axenic medium and in a cell model. In axenic medium, A. felis was susceptible to imipenem, aminoglycosides, and rifampin when using either the broth dilution technique or the agar technique. When grown in HeLa cells, A. felis was susceptible to amikacin and tobramycin but was resistant to the other compounds tested. Despite its intracellular location, A. felis can apparently be reached by aminoglycosides. Thus, the in vitro data presented here are in accord with the clinical data obtained in patients suffering CSD.

Anti-Bacterial Agents↗
PubMed1992

Phagolysosomal alkalinization and the bactericidal effect of antibiotics: the Coxiella burnetii paradigm.

Most infections due to intracellular bacteria respond poorly to antibiotic treatment. The chemical conditions within the subcellular site of bacteria may change antibiotic activity. Coxiella burnetii multiplies within phagolysosomes. The antimicrobial activity of antibiotics combined with the lysosomotropic agents amantadine (1 microgram/mL), chloroquine (1 microgram/mL), and ammonium chloride (1 mg/mL), which alkalinized Coxiella burnetii-containing phagolysosomes from pH 4.8 to 5.3, 5.7, and 6.8, respectively, was evaluated. Percentages of residual viable bacteria (RVB) in cell cultures were significantly reduced after exposure to combinations of doxycycline (4 micrograms/mL) with amantadine (RVB = 18.2% +/- 8.7%, P < .05), chloroquine (RVB = 0.64% +/- 0.38%, P < .01), or ammonium chloride (RVB = 0.29% +/- 0.17%, P < .01); the same was seen with pefloxacin (1 microgram/mL) with chloroquine (RVB = 27.6% +/- 10.8%, P < .05) or ammonium chloride (RVB = 3.72% +/- 1.1%, P < .05). Such bactericidal activity correlated with increased phagolysosomal pH, as determined by Pearson's correlation coefficient, suggesting that phagolysosomal alkalinization is critical for the bactericidal effect of antibiotics.

Amantadine↗
PubMed1992

Phagolysosomes of Coxiella burnetii-infected cell lines maintain an acidic pH during persistent infection.

Coxiella burnetii, the agent of Q fever, is an obligate intracellular bacterium that multiples within vacuoles of phagolysosomal origin. Persistently infected cell lines were maintained in continuous culture for months. We studied the pH of the phagolysosomes by using two murine cell lines during early propagation of the bacteria and after establishment of persistent infection. Three strains of C. burnetii were studied because of the purported propensity of each strain to cause acute or chronic disease and to be resistant or susceptible to antibiotics. The pHs were calculated from fluorescence experiments with fluoresceinated dextran as a lysosomal probe. Phagolysosomal vacuoles maintained an acidic pH during a 36-day infection. Minimal variation of the pH occurred over the duration of the experiment with strains that caused either acute or chronic disease. Phagolysosomal pH remained stable for as long as 153 days with the Nine Mile phase II isolate. Thus, neither the course of C. burnetti infection nor the diversity of antibiotic susceptibility of the strains is related to variations in the phagolysosomal pH.

Animals↗
PubMed1981

Mathematical models of the uptake of carbon monoxide on hemoglobin at low carbon monoxide levels.

Coburn's differential equation for the uptake of carbon monoxide by hemoglobin and two particular types of solution of this equation were considered and the solutions verified for a group of healthy adults consisting of 73 nonsmoking pedestrians or car passengers exposed to low levels of carbon monoxide as experienced in the city of Lyon. The CO levels at the breathing level and the walking speed of the subjects was continually measured, and the carboxyhemoglobin levels determined at the beginning and the end of each test journey. The values of all the other relevant parameters were also determined. The half-life of carboxyhemoglobin was studied as a function of the degree of activity, the age, the sex and the height of the subjects. Finally a mathematical model was set up to represent a periodic uptake of CO which made it possible to estimate the variations in the carboxyhemoglobin level for any subject during a period of a day or a week without any need to know the initial level.

Absorption↗