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Biomedical subjects

I Mortensen

Publications and source records attributed to I Mortensen.

At least 19 recordsLinked to original sources
PubMed1997

Evaluation of different methods for the detection of methicillin resistance in coagulase-negative staphylococci.

The efficacy of 19 agar diffusion methods for the detection of methicillin resistance among coagulase-negative staphylococci (CoNS) within 24 h was evaluated. A total of 359 CoNS isolates were tested, of which 204 were Staphylococcus epidermidis. In 164 isolates, the presence of mecA was investigated; 61 strains were mecA-positive and 103 were mecA-negative by Southern blot analysis. Based on the best agreement shown with the mecA determination (94%) among four agar dilution assays for determining methicillin MIC, an assay with Columbia agar supplemented with NaCl and incubation with a heavy bacterial inoculum of 10(5)-10(6) cfu/spot was used as the reference MIC method. The best agar diffusion results were obtained with a 1 microg oxacillin disc on Columbia agar with 4.5% NaCl supplement. With this method, 99% of S. epidermidis and 94% of non-S. epidermidis were in agreement with the MIC determination. However, Columbia (without NaCl), Mueller-Hinton and Isosensitest agars were almost as useful when a 1 microg oxacillin disc was used. The zone breakpoints for S. epidermidis were, in general, considerably larger than those for other CoNS species and, consequently, differentiation according to species is recommended. Furthermore, resistance to other antibiotics, such as gentamicin and erythromycin, makes methicillin resistance highly likely.

Bacterial Proteins↗
PubMed1996

In vitro susceptibility of 124 Xanthomonas maltophilia (Stenotrophomonas maltophilia) isolates: comparison of the agar dilution method with the E-test and two agar diffusion methods.

The in vitro susceptibility of 124 Xanthomonas maltophilia isolates was tested by four methods: Agar dilution (reference method), E-test, a disk diffusion and a tablet diffusion method. Trimethoprim-sulfamethoxazole had the highest activity against X. maltophilia, followed by a combination of aztreonam-clavulanic acid at different ratios, the ratio 1:1 being the most active with a susceptibility rate of 85% as compared to 2% for aztreonam alone. Addition of the beta-lactamase inhibitor tazobactam to piperacillin enhanced the rate of susceptible isolates from 31% to 53%, Relatively few isolates were susceptible to ciprofloxacin (27%) and gentamicin (9%). Generally, the disk diffusion method had a considerably higher frequency of "very major" discrepancies when compared with the agar dilution method than with the other methods. The susceptibility of X. maltophilia to trimethoprim-sulfamethoxazole and ciprofloxacin could reliably be determined by all the diffusion methods tested, but otherwise the agar dilution method is to be preferred. A standardized and reliable diffusion method for susceptibility testing of X. maltophilia remains to be found. Trimethoprim-sulfamethoxazole must be considered the drug of choice in the treatment of severe X. maltophilia infections. The combination aztreonam-clavulanic acid is promising, but must be proved in a clinical setting.

Anti-Bacterial Agents↗
PubMed1992

The antibacterial effect of some neuroleptics on strains isolated from patients with meningitis.

Eighty-two strains of bacteria (Neisseria meningitidis, Haemophilus influenzae, Enterobacteriaceae, Streptococcus pneumoniae, group B streptococci and Listeria monocytogenes) were examined for their in vitro susceptibility to eight drugs, seven neuroleptics (perphenazine, fluphenazine, cis(Z)-clopenthixol, haloperidol, clozapine, clebopride and SCH 23390), and the neuroleptically inactive trans(E)-clopenthixol. The phenothiazines and the thioxanthenes were, on the whole, the most active drugs when measured, the IC50(50) for each group of bacteria being 7.4 to 84 mg/l (with the exception of the activity against the enterobacteriaceae). The antibacterial potency of clozapine, which has an atypical neuroleptic profile, was between 50 and 140 mg/l. Haloperidol also showed an antibacterial activity in the concentration range 35-140 mg/l. The selective D1 antagonist, SCH 23390 and the selective D2 antagonist, clebopride, inhibited only few of the bacteria in the concentration range investigated.

Antipsychotic Agents↗
PubMed1991

Antibiotic susceptibility of invasive Haemophilus influenzae type b isolates in Denmark in 1988 and 1989.

A system for surveillance of invasive Haemophilus influenzae type b infections in Denmark yielded 135 strains isolated from blood or cerebrospinal fluid from August 1988 through December 1989. The susceptibility of the strains to 7 antibiotics was investigated by an agar dilution method. Ceftriaxone was found to be the most active drug followed by cefotaxime, ceftazidime, rifampicin, ampicillin, cefuroxime, and chloramphenicol. Except for ampicillin the MICs for the individual antibiotics were similar. Seven strains (5.2%), which all produced beta-lactamase, were resistant to ampicillin. Since H. influenzae type b meningitis in otherwise healthy individuals almost exclusively occurs in children aged 2 months to 4 years, a third generation cephalosporin such as ceftriaxone or cefotaxime may be considered the drug of choice for initial therapy of meningitis in this age group.

Ampicillin Resistance↗
PubMed1991

Mechanism of aminoglycoside resistance in Danish Staphylococcus aureus strains during the years 1979-1987.

A total of 49 gentamicin-resistant strains of Staphylococcus aureus isolated from blood (n = 26) or from other sites (n = 23) during the years 1979 to 1987 were evaluated for the presence of aminoglycoside-inactivating enzymes on the basis of minimum inhibitory concentrations measured by agar dilution as well as inhibition zone diameters determined by disc diffusion. Enzymatic activity was caused by AAC (6')III/APH (2") in 45 strains, and by AAC (6')III/APH (2") + APH (3') in four strains. No changes in the distribution of enzymatic activity were observed during the eight years.

Aminoglycosides↗
PubMed1988

In-vitro activity and beta-lactamase stability of methicillin, isoxazolyl penicillins and cephalothin against coagulase-negative staphylococci.

Forty-nine clinical strains of coagulase-negative staphylococci were investigated for susceptibility to methicillin, oxacillin, cloxacillin, dicloxacillin, flucloxacillin and cephalothin. The highest level of resistance was found to methicillin and the lowest to cephalothin. The resistance-level of the isoxazolyl penicillins showed a high degree of uniformity. However more strains were resistant to cloxacillin and oxacillin than to dicloxacillin and flucloxacillin. Only a weak correlation was found between beta-lactamase production, and resistance to the six antibiotics. Methicillin was the most stable. The inactivation of cephalothin differed from that of the other antibiotics.

Cephalothin↗
PubMed1987

Antibacterial effect of four phenothiazines.

Various types of phenothiazines were examined for antibacterial effect on 61 Gram-positive and Gram-negative bacterial strains in vitro. The investigated phenothiazines were two neuroleptic drugs, fluphenazine and chlorpromazine, and two antihistaminic drugs, alimemazine and promethazine. All four drugs have antibacterial effects in vitro, the phenothiazines being more potent against the Gram-positive microorganisms. The antibacterial potency of the drugs was measured as IC50: Fluphenazine 29 microM (15 micrograms/ml), alimemzaine 49 microM (37 micrograms/ml), promethazine 88 microM (28 micrograms/ml) and chlorpromazine 92 microM (29 micrograms/ml). The antibacterial potency of the drugs was linked neither to the neuroleptic nor the antihistaminic potency of the drugs, which is in agreement with results of earlier stereoisomeric investigations. Thus, the known phenothiazines may represent a pool of potentially new antimicrobial drugs. A therapeutic application of these results, however, requires additional in vitro an in vivo testing in an animal model. The bacterial model might be of value as a model system in the study of the interaction of neuropharmacological agents and other membrane active compounds on biological membranes.

Anti-Bacterial Agents↗
PubMed1987

The antibacterial activity of the psychopharmacological agent clopenthixol and its two main metabolites.

The antibacterial effect of the stereo-isomeric compounds cis(Z)- and trans(E)-clopenthixol and the two main metabolites of clopenthixol in man, N-dealkyl-clopenthixol and clopenthixol sulfoxide, was examined in 24 Gram-positive and 37 Gram-negative bacterial strains in vitro. The antibacterial potency of the drugs towards the Gram-positive strains, measured as IC50, was: N-dealkyl-clopenthixol, 6.2 microM (3.7 micrograms/ml), trans(E)-clopenthixol, 16 microM (7.6 micrograms/ml) and cis(Z)-clopenthixol, 37 microM (17.5 micrograms/ml), and clopenthixol sulfoxide was inactive in the investigated area. Against the Gram-negative strains the drugs are less potent. A therapeutic application of these results, especially in the case of trans(E)-clopenthixol, which possesses no neuroleptic activity, requires in vivo testing in an animal model. However, the in vitro model employed might also be useful in the study of such agents and other membrane-active compounds with regard to their interaction with biological membranes.

Anti-Bacterial Agents↗
PubMed1986

Susceptibility testing with disc diffusion for new cephalosporins: pre-diffusion revisited.

The purpose of the present study was to investigate the effect of 20-hour pre-diffusion, i.e. placing the antibiotic-containing discs on the agar for 20 hours prior to inoculation, as compared to direct diffusion, i.e. placing the discs on the agar immediately after inoculation, for the newer 3. generation cephalosporins as represented by ceftazidime and ceftriaxone. Regression lines (zone sizes vs. inhibitory concentrations, as measured by plate-dilution) were constructed for three groups of bacteria chosen because of their differences in growth characteristics on agar: E. coli (n = 50), Enterobacter sp. (n = 35), and streptococci (n = 51). The results for both cephalosporins were: 20-hour pre-diffusion produced larger zones than direct diffusion, regression studies for 20-hour pre-diffusion as compared to direct diffusion resulted in greater variation in zone sizes, numerically lower slopes, lower residual variances and higher correlation coefficients, and regression lines were significantly different for the 3 groups of bacteria with direct diffusion but not so with 20-hour pre-diffusion. Considering the interpretation of zone sizes with disc diffusion for the cephalosporins tested, 20-hour pre-diffusion was superior to direct diffusion.

Ceftazidime↗
PubMed1986

The antibiotic effect of the anti-depressive drug femoxetine and its stereo-isomeric analogs on diarrhoea producing enterobacteriaceae.

The present investigation has been undertaken to illustrate the antibacterial effect on 20 diarrhoea producing enterobacteriaceae of an anti-depressive drug available as femoxetine and its three analogs. It has been shown that the stereo-isomeric trans forms of femoxetine are more than twice as active as the cis forms and inhibited all the strains below 400 microgram/ml (1.2 mM). The two cis compounds only inhibited 11 and 9 of the 20 strains respectively in the investigated area 100 microgram/ml - 800 microgram/ml (0.3 mM - 2.4 mM). Our investigations point out that the bacterial cell has a target for psychopharmacologically active agents. Thus the known psychopharmaca and their stereo-isomeric analogs may represent a pool of potentially new antimicrobial drugs. Furthermore the bacterial model may be useful as a model system in the study of the interaction of neuropharmacological agents and other membrane active compounds with biological membranes.

Anti-Bacterial Agents↗
PubMed1985

Antibacterial activity in vitro and regression studies for ceftazidime and ceftriaxone.

The antibacterial activity in vitro of ceftazidime and ceftriaxone was investigated against 575 recent clinical isolates. Both cephalosporins displayed excellent activity against most of the pathogens tested, in particular Gram-negative bacteria, including Pseudomonas aeruginosa. Apart from the Pseudomonas group, Acinetobacter calcoaceticus and Campylobacter jejuni ceftriaxone was slightly to moderately more active than ceftazidime overall. Ceftriaxone was moderately active against Streptococcus faecalis. Regression lines for the two antibiotics were almost identical. Corresponding to differences in susceptibility, the zone sizes differed for the two drugs with respect to certain bacterial groups, e.g. Pseudomonas sp. and enterococci. Therefore, the two cephalosporins cannot substitute for each other in disc susceptibility testing. Breakpoints for disc tests around 8-16 micrograms/ml, as suggested in the literature, appear too high considering the beneficial pharmacokinetic properties of the two drugs.

Acinetobacter↗
PubMed1982

Membrane stabilizers inhibit potassium efflux from Staphylococcus aureus strain No. U2275.

The effect of different categories of membrane stabilizers on K+ loss and growth has been characterized in a culture of Staphylococcus aureus. Chlorpromazine, thiopental and tetracaine at low concentrations produced a marked inhibition of K+ loss and an equivalent increase in the K+ contents of S. aureus. Whereas the inhibitory effect of chlorpromazine on K+ loss was observed at lower than bacteriostatic concentrations of the drug, thiopental had no effect on growth in the concentration range where K+ loss was maximally inhibited. It is concluded that the bacteriostatic action of chlorpromazine is probably not related to its membrane stabilizing effect only.

Cell Membrane↗
PubMed1982

Experimental endocarditis in rabbits. 5. Results of long-term penicillin or streptomycin treatment of streptococcus faecalis endocarditis and the effect of long-term exposure of healthy rabbits to the same drugs.

A previously described model of experimental Streptococcus faecalis endocarditis in rabbits without an indwelling catheter during the infectious processes was used to study the effect of long-term treatment with antibiotics. Groups of animals infected with six different strains were treated for four weeks and the following parameters were determined: survival rate, bacterial concentration in blood and vegetations, signs at autopsy indicating congestive heart failure. Before the therapeutic experiments, the tolerance of the rabbit to long-term exposure of the drugs penicillin and streptomycin was considered in a group of non-infected animals. Two out of 20 rabbits died with enteritis during the penicillin exposure, and a general weight reduction was observed. Streptomycin was apparently completely harmless. There was no therapeutic effect of streptomycin on S. faecalis endocarditis due to strains all designated resistant to streptomycin by MIC, except in rabbits infected with a strain, which showed partial susceptibility to the drug by IC50. Regardless of the therapeutic effect, evidence was obtained for rapid development of increased resistance of the infecting strains towards streptomycin. After long-term treatment with penicillin in either low or high dose some of the animals survived and the valves were sterilized in 37% of the animals after low-dose and in 39% after high-dose. It was observed that congestive heart failure occurred with the greatest frequency and intensity after infection with proteolytic strains.

Animals↗
PubMed1981

Trichloroethylene: effects on body and organ weights in mice, rats and gerbils.

The influence of continuous inhalation of 150 ppm trichloroethylene (TCE) on body, liver, spleen, and kidney weights in rats, mice, and mongolian gerbils was tested. An age dependent decrease in body weight gain was observed in female rats exposed to TCE. All 3 species showed liver enlargement caused by the exposure. The effect was much more pronounced in mice, in which the increase was 60--80%, than in rats and gerbils where it was only 20--30%. After the end of the TCE-exposure the liver weights of the mice decreased rapidly. After 5 days of rehabilitation the weight was only 10--20% higher than that of the controls. This difference persisted for at least 25 days. The spleen weight appeared unaffected or somewhat smaller in TCE-exposed animals of all species. An increased kidney weight (15%) was observe din TCE-exposed gerbils. This effect was less pronounced in mice and rats. Effects on the liver have earlier been seen only after exposure to concentrations much higher than that used in the present study. This difference in results is proposed to be due to the different schedules used for the exposure.

Animals↗
PubMed1981

Stereo-isomeric dissociation of the antibacterial and the neuroleptic effect of clopenthixol.

Measurement of the IC50 of cis(Z)-clopenthixol and trans(E)-clopenthixol on 188 bacterial strains from human clinical specimens shows that the antibacterial activity of clopenthixol is exerted by both isomerical components and trans(E)-clopenthixol is the most active antibiotic of the two drugs against the sensitive strains. It is known that the trans(E)-clopenthixol isomere is without neuroleptic effect. The possibility of creating new antibiotics by e.g. steric alteration of neuroleptical agents is stressed. These drugs have different antibiotic patterns from those of classical antibiotics. It seems particularly promising that Pseudomonas aeruginosa is sensitive to these drugs.

Anti-Bacterial Agents↗
PubMed1980

In vitro comparison of gentamicin and netilmicin including a regression line for netilmicin.

The results of two different in vitro investigations are presented: a comparison between gentamicin and netilmicin and a presentation of a regression line for netilmicin. The first investigation comprises 335 bacterial strains. The method used is a plate dilution technique and the susceptibility of the strains is given as IC50 values, i.e. 50% inhibiting concentrations. The conclusion of the study is that netilmicin offers no advantage over gentamicin. In the second investigation a regression line is presented giving the relation between IC50 values for netilmicin and the size of the inhibition zone, based upon 109 bacterial strains. For the disc diffusion method a 20-hour prediffusion technique is used. The disc content is 15 micrograms netilmicin base. The results are discussed and a grouping as to susceptibility is proposed based on the IC50 values found and the blood level obtained after scheduled dose of netilmicin.

Dose-Response Relationship, Drug↗