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Biomedical subjects

M F Michel

Publications and source records attributed to M F Michel.

At least 37 records · Page 2Linked to original sources
PubMed1992

Factors influencing the infectivity of Chlamydia pneumoniae elementary bodies on HL cells.

The influence of variations in the pH, NaCl concentration, temperature, and concentrations of calcium and magnesium ions on the survival of Chlamydia pneumoniae elementary bodies (EBs) outside the host cells was investigated. The survival was determined after various incubation periods by counting the inclusion-forming units after C. pneumoniae was cultured for 72 h on monolayers of HL cells. The normal physiological conditions were restored prior to infecting the HL cells with C. pneumoniae. Declines in the infectivities of C. pneumoniae EBs were observed at pH values of lower than 5 and higher than 8 or at NaCl concentrations of less than 80 mM. The viability of C. pneumoniae EBs in SPG medium decreased as the temperature and/or incubation period increased. Incubation temperatures of up to 20 degrees C and incubation periods of up to 48 h did not affect the viability of C. pneumoniae. One hundred percent of the C. pneumoniae EBs were infective after 1 h of incubation at 35 degrees C, whereas 90, 50, and 40% survived after incubations of 8, 24, and 48 h, respectively. The viability of C. pneumoniae was unaffected within the investigated range of Ca2+ and Mg2+ ion concentrations in the medium. The presence of 10% fetal calf serum in the incubation medium had a stabilizing effect on the viability of C. pneumoniae. This effect became more pronounced as the incubation period increased.

Calcium↗
PubMed1991

An alternative approach for gene transfer in trees using wild-type Agrobacterium strains.

Micropropagated shoots of three forest tree species, poplar (Populus tremula x P. alba), wild cherry (Prunus avium L.) and walnut (Juglans nigra x J. regia), were inoculated each with six different wild-type Agrobacterium strains. Poplar and wild cherry developed tumors that grew hormone-independently, whereas on walnut, gall formation was weak. On poplar and wild cherry, tumors induced by nopaline strains developed spontaneously shoots that had a normal phenotype and did not carry oncogenic T-DNA. From these observations, we have established a co-inoculation method to transform plants, using poplar as an experimental model. The method is based on inoculation of stem internodes with an Agrobacterium suspension containing both an oncogenic strain that induces shoot differentiation and a disarmed strain that provides the suitable genes in a binary vector. We used the vector pBI121 carrying neo (kanamycin resistance) and uidA (beta-glucuronidase) genes to facilitate early selection and screening. Poplar plants derived from kanamycin-resistant shoots that did not carry oncogenic T-DNA, were shown to contain and to express neo and uidA genes. These results suggest that wild-type Agrobacterium strains that induce shoot formation directly from tumors can be used as a general tool for gene transfer, avoiding difficult regeneration procedures.

Culture Techniques↗
PubMed1991

Growth characteristics and metastatic potential of seven intestinal carcinoma lines serially passaged in syngeneic rats.

Transplantable tumour lines were obtained from one duodenal carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine in the Lewis rat and from six colonic carcinomas induced by 1,2 dimethylhydrazine in BDIX or Fisher rats. The tumours were serially transplanted by the subcutaneous route into homologous syngeneic rats. The seven tumours differ from one another in their histological structure, five of them being well or moderately differentiated adenocarcinomas, and in their capacity to produce neutral or acidic mucins. The seven tumours also differ in their growth rate. The seven lines produced metastases; the metastatic potential and the location of the metastases differed from one line to another. The seven lines kept their original differentiation characteristics through multiple passages, representing several years of transplantation into syngeneic hosts. These tumours represent a useful and diversified model of metastatic intestinal carcinoma, available for basic research and therapeutic trials.

Animals↗
PubMed1991

Distribution, antibiotic susceptibility and tolerance of bacterial isolates in culture-positive cases of endocarditis in The Netherlands.

During a two-year period data were collected nationwide in The Netherlands on 438 episodes of bacterial endocarditis (BE) in 432 patients. Of the strains isolated in these patients 419 were available for analysis. Of these, 326 were isolated in native valve endocarditis (NVE) and 93 in prosthetic valve endocarditis (PVE). Viridans streptococci, staphylococci and enterococci together constituted 87% of the isolates. More than 46% of the viridans streptococci consisted of Streptococcus sanguis. Enterococcus faecalis and Staphylococcus aureus were the predominant species in the late form of PVE. The majority of the viridans streptococci and haemolytic streptococci were highly susceptible to penicillin. Five of 35 strains of coagulase negative staphylococci were resistant to methicillin. Eleven percent of a random sample of the streptococci collected were tolerant to penicillin. After repeated exposure to a concentration gradient of an appropriate beta-lactam antibiotic, this figure increased to 49%. Of the staphylococci, 5-6% of the strains were tolerant before induction and 16-20% after induction. Of the Enterococcus strains (n = 40), 12.5% showed high-level resistance to one or more aminoglycoside.

Drug Resistance, Microbial↗
PubMed1991

Impact of the duration of infection on the activity of ceftazidime, gentamicin and ciprofloxacin in Klebsiella pneumoniae pneumonia and septicemia in leukopenic rats.

An experimental Klebsiella pneumoniae pneumonia and septicemia in leukopenic rats was used to study the impact of the duration of infection on the bactericidal activity of ceftazidime, gentamicin and ciprofloxacin. It appeared that the number of bacteria persisting after a single intravenous injection progressively increased with delay of antibiotic administration up to 3 h after bacterial inoculation with each of the drugs tested. This effect was most pronounced for ciprofloxacin. An inoculum effect could not explain this decrease in bacterial killing. It was also observed that a single injection with a particular dose of each of the respective drugs did not kill all the Klebsiella pneumoniae organisms in the lung. Persisting bacteria did not represent a preexisting less susceptible subpopulation selected after antibiotic administration. In further experiments the impact of delay of the start of treatment on the efficacy of ceftazidime or ciprofloxacin after administration for a period of four days with intramuscular injections at 6 h intervals was investigated. Treatment was started at 5, 12 or 24 h after bacterial inoculation. The therapeutic efficacy of both drugs decreased with the increase of duration of infection, which may be at least in part due to the progressive number of bacteria persisting after antibiotic administration. These data underline the need to start antimicrobial treatment as soon as possible.

Animals↗
PubMed1991

Role of tolerance in cloxacillin treatment of experimental Staphylococcus aureus endocarditis.

The role of Staphylococcus aureus tolerance was investigated in endocarditis in rats. The efficacies of cloxacillin, gentamicin, and a combination of the two were compared for animals infected with a tolerant strain, its kill-sensitive variant, or a nonisogenic nontolerant strain of S. aureus. Cloxacillin was significantly less effective for treating the tolerant than for the nontolerant strains. The addition of gentamicin to cloxacillin reduced bacterial numbers in endocardial vegetations for the tolerant strain comparable to the reduction by cloxacillin alone for the nontolerant strains, but had no additional effect for the nontolerant strains. Isolates from animals infected with the tolerant or nontolerant strains during antibiotic treatment remained tolerant or nontolerant. These results show that the in vitro phenomenon of tolerance is relevant in vivo.

Animals↗
PubMed1991

Pharmacokinetics of meropenem in serum and suction blister fluid during continuous and intermittent infusion.

The pharmacokinetics and penetration into suction blister fluid of meropenem was investigated after intermittent (10 mg/kg/6 h) and during continuous infusion (10 mg/kg/6 h) in eight healthy male volunteers in a crossover fashion. Concentrations in serum, urine and blister fluid were determined by a HPLC method. The pharmacokinetic parameters in serum (+/- S.D.) T1/2 beta, AUC and clearance after the third dose of intermittent infusion were 62.7 (11.4) min, 43.5 (7.1) mg.h/L and 292.1 (36.8) mL/min respectively. The penetration in blister fluid was rapid and good, with a AUC ratio blister fluid/serum of 84.7 (11.4)%. During continuous infusion, from 12 to 18 h after the start of the infusion, the mean concentration in serum was 6.3 (0.7, S.D.) mg/L and in blister fluid 5.4 (0.7, S.D.) mg/L. The clearance was 338.3 (45.6) mL/min for serum. Urinary recovery was 61.6 (8.7)% after intermittent and 61.9 (6.9)% after continuous infusion.

Adult↗
PubMed1991

Performance of a nonisotopic DNA probe for detection of Chlamydia trachomatis in urogenital specimens.

The Gen-Probe PACE 2 assay (GP), a nonisotopic DNA probe, was evaluated by using cell culture as the method of reference. Specimens were collected from 260 men and 482 women visiting the outpatient department for sexually transmitted diseases at the University Hospital in Rotterdam, The Netherlands. The prevalences of Chlamydia culture-positive men and women were 13.2 and 8.6%, respectively. Sensitivity values for the male and female patients were 70.6 and 92.7%, respectively. Specificity values for these groups were 98.2 and 97.7%, respectively. Sensitivity was significantly lower when the number of inclusions in cell culture was low. Samples which showed a discordance between cell culture and GP results were retested by the polymerase chain reaction. If the results of the polymerase chain reaction were considered as the points of reference, the sensitivity and specificity of both GP and cell culture could be calculated. The performance of GP for females was comparable to that of cell culture. In males, the sensitivity of GP was considerably lower than that of cell culture (77.2 versus 91.4%), while specificity was somewhat higher (99.6 versus 99.1%). Compared with cell culture, the GP is a relatively simple and rapid test that is suitable for diagnosing Chlamydia infections in urogenital specimens.

Base Sequence↗
PubMed1990

Detection of an antibody response in immunocompetent patients with systemic candidiasis or Candida albicans colonisation.

Tests to detect circulating antibodies to Candida albicans antigens were performed in sera from 27 immunocompetent patients, 15 of whom had deep-seated candidiasis and 12 of whom were colonised by Candida albicans. For the diagnosis of deep-seated candidiasis in patients with either deep-seated candidiasis or Candida albicans colonisation, counterimmunoelectrophoresis had a sensitivity of 87% and a specificity of 75%. Using immunoblotting it could be shown that antibodies to 35K, 47K, 68K and 88K antigens of Candida albicans occurred more frequently in patients with deep-seated candidiasis than in colonised patients. The presence of dense bands in immunoblots representing antibodies against the 47K and/or 68K antigen served to discriminate significantly between deep-seated and superficial candidiasis (p less than 0.05).

Antibodies, Fungal↗
PubMed1990

Comparison of clinical Acinetobacter strains using a carbon source growth assay.

A quantitative carbon source growth assay, comprising ten carbon sources, was used to compare acinetobacter strains from three hospitals. The strains had been obtained during episodes of increased prevalence of isolations and were, for each hospital, assumed to be epidemiologically related. This assumption was supported by the electrophoretic protein profiles of the strains. Univariate analysis of growth data showed significant differences between strains from the three hospitals. Moreover, cluster analysis revealed that the major pattern in the data was related to the epidemiological origin of the strains. Exceptions to the epidemic-related pattern were observed. Thus, apart from epidemiological factors, other factors might contribute to carbon source growth profiles of the strains. It is concluded that the carbon growth assay may be useful to distinguish roughly between acinetobacter strains from different sites of origin. Further studies are required to analyse additional factors which influence carbon source growth of strains.

Acinetobacter↗
PubMed1990

Pefloxacin compared with cefotaxime for treating men with uncomplicated gonococcal urethritis.

In a randomized comparative study, 83 male patients suffering from acute uncomplicated gonococcal urethritis were treated with a single dose of either 0.8 g pefloxacin, given orally, or 1.0 g cefotaxime, given intramuscularly. The cure rates were 100% in both treatment groups four to seven days and 21 to 31 days, respectively, after therapy. The MICs of the isolated Neisseria gonorrhoeae ranged from 0.008 to 0.06 mg/l for pefloxacin and from 0.0005 to 0.03 mg/l for cefotaxime. Postgonococcal urethritis was found in 9% of the patients treated with pefloxacin and in 20% of the patients treated with cefotaxime. Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum were isolated from 15%, 7% and 22% of the patients, respectively, before therapy and from 22%, 11% and 20% of the patients, respectively, 21 to 31 days after therapy. Both antibiotics had no effect on the presence of these microorganisms. No side effects were recorded in either groups of patients except that 46% of the patients treated with cefotaxime reported mild pain at the injection site. In conclusion, pefloxacin and cefotaxime are safe and effective agents in the treatment of uncomplicated gonococcal urethritis in men.

Administration, Oral↗
PubMed1990

Ecology of Pseudomonas aeruginosa in patients with cystic fibrosis.

The occurrence of various Pseudomonas aeruginosa strains in the sputum of 15 patients with cystic fibrosis (CF) was monitored over periods ranging from 2 to 60 months. Isolates of P. aeruginosa were typed by four different techniques, namely serotyping, active and passive pyocin typing, and phage typing. The maximum number of different serotypes found in the patients was three (one serotype in nine patients; two serotypes in five patients; three serotypes in one patient). Pyocin and phage typing showed no marked differences between strains of the same serotype in individual patients. Exacerbations of chronic respiratory infection were not associated with changes in the sputum flora, the composition of P. aeruginosa strains in which remains constant over long periods in patients with CF.

Adolescent↗
PubMed1990

Pharmacokinetics of ceftazidime in serum and suction blister fluid during continuous and intermittent infusions in healthy volunteers.

The pharmacokinetics of ceftazidime were investigated during intermittent (II) and continuous (CI) infusion in eight healthy male volunteers in a crossover fashion. The total daily dose was 75 mg/kg of body weight per 24 h in both regimens, given in three doses of 25 mg/kg/8 h (II) or 60 mg/kg/24 h with 15 mg/kg as a loading dose (CI). After the third dose (II) and during CI, serum and blister fluid samples were taken. Seven new blisters were raised for each timed sample by a suction blister technique. Blisters took 90 min to form. Samples were then taken from four blisters (A samples) and 1 h later were taken from the remaining three (B samples). The concentration of ceftazidime was determined using a high-performance liquid chromatography method. After II, the concentrations in serum immediately after infusion (t = 30 min) and 8 h after the start of the infusion were 137.9 (standard deviation [SD], 27.5) and 4.0 (SD, 0.7) micrograms/ml, respectively. The half-life at alpha phase (t1/2 alpha) was 9.6 min (SD, 4.6), t1/2 beta was 94.8 min (SD, 5.4), area under the concentration-time curve (AUC) was 285.4 micrograms.h/ml (SD, 22.7), total body clearance was 0.115 liter/h.kg (SD, 0.022), and volume of distribution at steady state was 0.178 liter/kg (SD, 0.023). The blister fluid (A) samples showed a decline in concentration parallel to that of the concentrations in serum during the elimination phase with a ratio of 1:1. The t1/2 of the A samples was 96.4 min (SD, 3.2). The concentration of ceftazidime in the B blister fluid samples was significantly higher (27%) than in the A samples over time. This shows that blisters may behave as a separate compartment and establishes the need to raise new blisters for each timed sample. The mean AUC/h during continuous infusion was 21.3 micrograms . h/ml (SD, 3.0). The total body clearance was 0.113 liter/h . kg (SD, 0.018), the urinary clearance was 0.105 liter/h . kg (SD, 0.012), and the ceftazidime/creatinine clearance ratio was 0.885. The mean AUC of blister fluid per hour was 84.5% (18.0 micrograms . h/liter; SD, 3.6) compared with that of serum. The A samples did not differ significantly from the B samples. The implications of continuous infusion of beta-lactams for treatment of serious infections are discussed.

Adult↗
PubMed1990

Different doses of cefetamet pivoxil (Ro 15-8075) in the treatment of acute uncomplicated gonococcal urethritis in men.

In an open, dose-finding study, a 100% cure rate was observed in patients suffering from uncomplicated gonococcal urethritis who were treated with a single oral dose of either 1.2 g (n = 10), 0.8 g (n = 11), or 0.4 g (n = 10) of cefetamet pivoxil. The MICs of cefetamet for all gonococcal strains ranged from 0.001 to 0.12 micrograms/ml, and the MIC for 90% of the strains tested was 0.008 micrograms/ml. Cefetamet pivoxil was ineffective against Chlamydia trachomatis in 3 of 31 patients. Side effects were minor.

Administration, Oral↗
PubMed1990

Identification of different agrobacterium strains isolated from the same forest nursery.

Several Agrobacterium strains isolated from the same forest nursery from 1982 to 1988 were compared by serological, biochemical, and DNA-DNA hybridization methods. Similarities among strains belonging to biovar 2 were observed by indirect immunofluorescence, whereas biovar 1 strains showed serological heterogeneity. Electrophoretic analysis of bacterial envelope-associated proteins showed that few bands appeared in the strains belonging to biovar 1, whereas many proteins appeared in the case of biovar 2 strains. Chromosomal DNA was analyzed with six random C58 chromosomal fragments. None of the six probes hybridized to the DNA of the two biovar 2 strains. One of the probes gave the same hybridization pattern with all biovar 1 strains, whereas the other probes yielded different patterns. The vir regions were closely related in the different pathogenic strains. The T-DNA and replication regions were less conserved and showed some variations among the strains.

Journal Article↗
PubMed1990

Screening for cervical Chlamydia trachomatis infections in two Dutch populations.

Endocervical cultures for Chlamydia trachomatis and Neisseria gonorrhoeae were taken from 492 women attending an outpatient clinic for sexually transmitted diseases (group I) and 560 women seeking legal abortion (group II). Possible risk factors for C trachomatis infection were evaluated by multivariate analysis. The prevalence rates for C trachomatis and N gonorrhoeae were 7.3% and 2.5% in group I and 9.4% and 0.4% in group II. From multivariate analysis it was found that age (p less than 0.01), number of sexual partners (p less than 0.01), abnormal vaginal discharge (p less than 0.01), and endocervical mucopus (p = 0.02) were independently associated with chlamydial infection in group I. In the abortion clinic age (p = 0.03) and endocervical mucopus (p = 0.03) were the only significant independent predictors of C trachomatis. In all women vaginal discharge was collected for Gram staining. A significant higher number of polymorphonuclear cells was seen in the smears of C trachomatis positive women (group I: p = 0.04; group II: p = 0.03). In group II there was also a significant association between C trachomatis and Gardnerella type bacterial flora (p = 0.02) and the presence of comma-shaped rods (p = 0.04). Screening for C trachomatis infection may help to decrease the incidence of (post-abortal) pelvic inflammatory disease. Because screening in abortion clinics is not always possible, decreasing the incidence of postabortal pelvic inflammatory disease could be achieved by using prophylactic antibiotics. Selective use of prophylaxis in high risk patients can minimise costs and the incidence of side effects.

Adult↗