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Biomedical subjects

M F Michel

Publications and source records attributed to M F Michel.

At least 109 records · Page 6Linked to original sources
PubMed1984

Responses of tolerant and nontolerant Staphylococcus aureus strains to methicillin treatment in an experimental infection in mice.

Staphylococcus aureus strains can be divided into tolerant and nontolerant strains on the basis of their survival in vitro in the presence of high concentrations of methicillin (greater than or equal to 64 micrograms/ml). A strain is defined as tolerant if more than 2% of the inoculum survives under these conditions. The response of five susceptible and five tolerant S. aureus strains to treatment with methicillin was studied in an experimental thigh infection in mice. Animals were treated with one and two injections of methicillin (2.5 mg per mouse). At the end of treatment, the number of CFUs in the thigh muscles infected with the susceptible strains was found to be significantly lower than that in the thigh muscles infected with the tolerant

Animals↗
PubMed1984

Survival of Chlamydia trachomatis in different transport media and at different temperatures: diagnostic implications.

We compared the survival of a laboratory strain of Chlamydia trachomatis serovar L-2 in different media and at different temperatures (room temperature, 4 degrees C, and -70 degrees C). At these temperatures the best storage medium was 2SP (0.2 mol/l sucrose in 0.02 mol/l phosphate buffer supplemented with 10% fetal calf serum). We used material obtained from patients to study the sensitivity of the culture method as a function of sample storage time and temperature. Compared with results on direct inoculation, material stored in 2SP for 48 hours gave 11% fewer positive cultures at 4 degrees C and 14% fewer at room temperature. Of samples which gave negative results on direct inoculation, 4% were positive after storage at 4 degrees C for 48 hours and 2% after storage at -70 degrees C for a week. As expected, the number of inclusion forming units in the original material proved to be important for the percentage of positive cultures among the stored samples.

Bacteriological Techniques↗
PubMed1984

Clinical application of amikacin dosage based upon lean body mass in patients with different renal function.

To determine an adequate dosage of amikacin, a pharmacokinetic model was used based on lean body mass (LBM), age and serum creatinine. Amikacin was administered during a mean period of 7 days to patients with normal (group I, n = 15, CCr greater than 60 ml/min), impaired stable (serum creatinine within a range of 50 mumol/l), (group II, n = 10) and unstable (group III, n = 8) renal function. The mean trough and peak blood levels were less than 2 and 24, 4.5 and 25 and 7 and 26 micrograms/ml in groups I, II and III, respectively. In group II and III a maximum trough level of 10 instead of 5 micrograms/ml was permitted to prevent a prolonged period of low subtherapeutic levels. With this modification the regimen in both groups appeared satisfactory. The pharmacokinetic model allows an accurate dosage regimen in all groups and can easily be programmed into a pocket calculator.

Adolescent↗
PubMed1984

Rifampicin and rifapentine in treatment of experimental listeriosis in normal mice and athymic (nude) mice.

Rifampicin and rifapentine were used in the treatment of Listeria monocytogenes infections in normal mice and congenitally athymic (nude) mice. Results were compared with untreated controls and with the results obtained from a previous study of ampicillin in which this model was used. Low doses of rifampicin or rifapentine were adequate to cure normal mice. The efficacy of these antibiotic treatment schedules was lost in nude mice. Prolonged antibiotic treatment schedules with increased dosages were also unsuccessful. These studies show that rifampicin and rifapentine , two antimicrobial agents being capable of destroying intracellular bacteria, were not effective in curing the Listeria infection in mice with impaired host defenses.

Animals↗
PubMed1983

Resistance of Escherichia coli in faeces and the use of antimicrobial agents in the treatment of hospital patients.

Resistance of faecal Escherichia coli to ampicillin, tetracycline, sulphamethoxazole and gentamicin was studied in patients admitted to seven different departments in two hospitals. The resistance of ampicillin, tetracycline and sulphamethoxazole in the seven patient groups was 27-57%, 26-56% and 35-63%, respectively. Resistance to gentamicin was found in only one department. An E. coli flora predominantly resistant to ampicillin, tetracycline or sulphamethoxazole (greater than 50% of the E. coli strains in a faecal sample resistant) was found in 10-38%, 4-30% and 21-35% of the samples. A cross-sectional study focusing on the influence of the use of antimicrobial agents on the occurrence of resistant strains revealed a positive correlation between the annual turnover of broad-spectrum penicillins in various departments and the occurrence of predominantly ampicillin-resistant E. coli strains in these departments.

Ampicillin↗
PubMed1983

Faecal carriage of aerobic gram-negative bacilli and drug resistance of Escherichia coli in different age-groups in Dutch urban communities.

Faecal carriage rates for aerobic gram-negative bacilli and for antibiotic-resistant Escherichia coli were determined in samples of the Dutch urban population. Of the 741 people studied, 64 were under 1 year old (infants), 53 were 1-5 years old, and there were approximately 200 in each of the age-ranges 6-17 years, 18-49 years and 50-80 years. Carriage rates of E. coli were similar (87-93%) in all age groups, but Klebsiella and Enterobacter species were found more often in specimens from infants and young children than in those from older people. E. coli strains resistant to tetracycline, ampicillin, or sulphamethoxazole or to any one or more of them were detected in 42%, 26%, 46% and 66% respectively of the specimens found to contain E. coli. The corresponding figures for the finding of E. coli populations that were predominantly resistant to tetracycline, ampicillin or sulphamethoxazole were 12%, 6% and 20%. The frequency of resistance to any of these drugs was not related to age or sex of the subjects. All E. coli isolates were sensitive to gentamicin. Among the 577 subjects aged 6-80 years from whose samples E. coli was isolated were 19 who had taken antibacterial drugs in the previous 30 days and 11 who were involved in cattle farming; carriage rates for tetracycline-resistant and sulphonamide-resistant E. coli were significantly higher among these 30 than in the other 547.

Adolescent↗
PubMed1983

Quantitative study of the aerobic and anaerobic faecal flora in neonatal necrotising enterocolitis.

Faeces from 24 neonates with proved necrotising enterocolitis (NEC), from 12 with clinically suspected NEC, and from 41 control infants were quantitatively cultured under aerobic and anaerobic conditions. An important difference in colonisation with Klebsiella was found between the NEC groups and the control group. Although the cause of NEC is unknown, colonisation with Klebsiella seems to increase the risk.

Aerobiosis↗
PubMed1983

Gonococcal serology. A comparison of three different tests.

Three serological tests for the detection of gonococcal antibodies were compared: an enzyme-linked immunosorbent assay (ELISA), an indirect haemagglutination reaction (IHA), and a gonococcal complement-fixation test (GCFT). The ELISA was performed with gonococcal pili of a Rotterdam strain (1443) as antigen, the IHA with pilus antigen of an American strain (2686, Buchanan), and the GCFT with whole gonococci of a single strain (46695, Oliver) as antigen. The tests were performed on sera from the same groups of Dutch patients; samples of sera were taken at the first examination and generally 11-22 days later. The ELISA and the IHA were more sensitive than the GCFT. The specificity of the tests was equal in low-risk groups, but the GCFT was slightly more specific in high-risk groups. The ELISA and the IHA did not differ in sensitivity and specificity. The agreement between the ELISA and IHA for patients with uncomplicated gonorrhoea was low (chi = 0.44), but the agreement between the GCFT and the two pilus assays was less (chi = 0.26 and 0.20). The sensitivities were highest for sera from patients with oropharyngeal gonorrhoea or with gonococcal complications; again the ELISA and the IHA were more sensitive than the GCFT.

Adult↗
PubMed1983

Antibodies to gonococcal pili in women with asymptomatic gonorrhoea. Diagnostic value of the ELISA for testing women attending an STD clinic.

The diagnostic efficacy of an enzyme-linked immunosorbent assay (ELISA) using gonococcal pili 6650 as antigen was studied in asymptomatic women attending an STD clinic. Of the 182 women studied, gonorrhoea was diagnosed in 29%. The value of the ELISA was calculated on the basis of four arbitrary cut-off points in the test. The best predictive values for a positive result (PV(+)) were obtained at an absorbance value of A greater than or equal to 1.15 and A greater than or equal to 1.30 and that for a negative result at A greater than or equal to 0.85. When patients with a history of gonorrhoea were excluded, the PV(+) rose only at A greater than or equal to 1.15 (not at A greater than or equal to 1.30) and the PV(-) rose slightly. To be of use in the diagnosis of gonorrhoea in asymptomatic patients the ELISA should be used as follows: the result is positive at A greater than or equal to 1.15 and negative at A less than 0.85, the PV(+) then being 0.52 and the PV(-) 0.85. Whenever sera give a result between A = 0.85 and A = 1.15, the test should be repeated.

Antibodies, Bacterial↗
PubMed1983

Enzyme-linked immunosorbent assay for detecting gonococcal antibodies using two antigenically different gonococcal pili as antigen.

Antibodies to pilar antigens of two gonococcal strains isolated in Rotterdam (6650 and 1443) were detected using enzyme-linked immunosorbent assays (ELISA). Paired sera (the first sample taken at the first examination (D1) and the second 11-22 days later (D2)) from women with and without gonorrhoea attending a sexually transmitted disease (STD) clinic were studied. The sensitivity of the ELISA using gonococcal pili 6650 as antigen (ELISA 6650) was significantly higher than that using gonococcal pili 1443 as antigen (ELISA 1443). The specificity of the two tests differed little. On D1 the sensitivity in women with uncomplicated gonorrhoea was 69% in the ELISA 6650 and 45% in the ELISA 1443; the corresponding values in asymptomatic infected women were 75% and 57% respectively. The agreement (both in positive and in negative results) between the two tests was less than might have been expected (kappa = 0.41).

Antibodies, Bacterial↗
PubMed1982

Intrarenal distribution of ampicillin in the healthy and the infected rat kidney: a comparison of methods.

The ampicillin concentration in the cortex of the normal and the infected rat kidney was determined by means of three different methods: tissue homogenate analysis, renal lymph analysis, and autoradiography. Both tissue homogenate analysis and autoradiography revealed that the cortical ampicillin concentration was about five times as high as the serum concentration. Renal lymph analysis disclosed that the ampicillin concentration in this fluid amounted to about 93% of the serum concentration. The discrepancy between these results can be explained on the basis of the binding of ampicillin to cellular components in the cortex. The results of the study of ampicillin distribution in infected rat kidneys with the aid of tissue homogenate analysis and autoradiography indicate that the ampicillin concentration was lower in the affected than in the intact tissue. Renal lymph analysis showed that the ampicillin concentration in the lymph was not affected by the presence of the infection. Quantitative autoradiography demonstrated that the ampicillin concentration in the cortical foci of infection was of the same order of magnitude as the serum concentration. For this kind of study autoradiography together with lymph analysis are recommended.

Ampicillin↗
PubMed1982

Demonstration of antigenic heterogeneity of Neisseria gonorrhoeae pili antigens using human sera in the test system.

Antigenic heterogeneity of gonococcal pili using human sera in the test system was demonstrated by means of indirect haemagglutination (IHA) inhibition studies. The reactivities of sera from 104 females with current gonococcal infection were compared by the IHA test using different pili preparations as antigens. Sera and gonococcal strains were collected from 365 patients. Pili were purified from strains infecting patients who met the following three requirements: 1) no history of previous gonococcal infection(s), 2) an infection that had lasted a week or more, 3) a seronegative result when tested by the IHA test using pili from Buchanan's strain 2686 as antigen. Each patient's serum was tested against pili produced by the gonococcal strain infecting this particular patient. A seropositive reaction obtained by using pili antigen from the strain infecting the seronegative (strain 2686) patient indicates an antigenically heterogeneous pili preparation. Two such strains, antigenically different from one another and from strain 2686, were found among 22 pili preparations investigated.

Animals↗
PubMed1982

Factors influencing detection of tolerance in Staphylococcus aureus.

The phenomenon of tolerance to cloxacillin and methicillin was studied in Staphylococcus aureus. It was demonstrated that the minimal bactericidal concentrations showed marked differences, depending on the method of detection used. These differences resulted from carry-over of the antibiotic to the subculture plates. When carry-over of the antibiotic was prevented by the addition of beta-lactamase to the nutrient medium, the antibiotics were no longer bactericidal. At a certain antibiotic concentration and at higher concentrations, however, each strain showed a certain survival percentage after 24 h. The tolerance percentage was determined for 15 strains. The values found for the individual strains ranged from less than 0.1 to 11% for cloxacillin and methicillin. since these percentages were reproducible within narrow limits, they could be regarded as a characteristic of the strains. The tolerance percentage was independent of the growth phase of the initial cultures.

Anti-Bacterial Agents↗
PubMed1982

Ampicillin susceptibility and ampicillin-induced killing rate of Escherichia coli.

The killing rate induced by ampicillin was determined in 20 strains of Escherichia coli. The apparent generation rate constant for each E. coli showed a characteristic concentration-dependent course. This course can be mathematically described and is determined by four parameters. Three of these parameters determine the speed of the process, and the fourth parameter determines a minimal concentration. The susceptibility of the strains, measured as the minimal inhibitory concentration by an agar dilution method, correlated with the minimal concentration and with a minimal inhibitory concentration calculated from the curve, but not with the rate-determining parameters.

Ampicillin↗