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Biomedical subjects

D J Krogstad

Publications and source records attributed to D J Krogstad.

At least 73 records · Page 4Linked to original sources
PubMed1984

Laboratory evaluation of five assay methods for vancomycin: bioassay, high-pressure liquid chromatography, fluorescence polarization immunoassay, radioimmunoassay, and fluorescence immunoassay.

We compared the precision and accuracy of five methods used to measure the concentration of vancomycin in serum: bioassay, high-pressure liquid chromatography, fluorescence polarization immunoassay (FPIA [TDX; Abbott Laboratories, North Chicago, Ill.]), radioimmunoassay (RIA), and fluorescence immunoassay. Based on an analysis of seven standards and of 106 patient samples, all five methods were accurate, and four (bioassay, high-pressure liquid chromatography, FPIA, and RIA) were also precise. The FPIA was the most precise and the fluorescence immunoassay was the least precise of the methods tested; intrarun coefficients of variation for these two methods were 0.9 to 3.0% versus 8.9 to 14.5%, and interrun coefficients of variation were 2.8 to 8.1% versus 12.2 to 16.2%, respectively. The RIA was inconvenient because it required an extra dilution of the specimen being tested and an additional (64 micrograms/ml) vancomycin standard for specimens with 32 to 64 micrograms of vancomycin per ml. Based on its rapid turnaround time and the stability of its standard curve, we believe that the FPIA is the best method currently available to quantitate vancomycin in the clinical laboratory.

Biological Assay↗
PubMed1983

Treatment of chloroquine-resistant malaria during pregnancy.

A pregnant 36-year-old Vietnamese refugee with chloroquine-resistant Plasmodium falciparum infection was treated with pyrimethamine and a sulfonamide. This treatment produced rapid clearance of the patient's parasitemia and was associated with a resumption of normal fetal and uterine growth. Because the other drugs effective against chloroquine-resistant P falciparum may produce uterine stimulation (quinine sulfate) or damage the fetal skeleton (tetracyclines), the pyrimethamine-sulfonamide combination (with folinic acid supplementation) may be the best available choice for the treatment and prophylaxis of chloroquine-resistant P falciparum infection in pregnancy, despite its theoretical risk of teratogenicity.

Adult↗
PubMed1983

Spectrophotometric assessment of dose-response curves for single antimicrobial agents and antimicrobial combinations.

The activity of single antimicrobial agents and antimicrobial combinations was examined by measuring their effects on the growth rate constant of a test strain of Escherichia coli. This spectrophotometric method provides a kinetic view of antimicrobial action and is sufficiently precise to define dose-response curves, in contrast to standard methods such as broth or agar dilution testing, which are static and measure only all-or-none responses. The results demonstrate that dose-response curves for single antimicrobial agents are logarithmic (rather than linear) and that the effects of antimicrobial combinations may be exquisitely concentration dependent. Although the results for some antimicrobial combinations were similar with the spectrophotometric and checkerboard methods, other combinations produced different results in the two systems. Additional studies will be necessary to determine whether one or the other of these methods more accurately predicts clinical outcome.

Anti-Bacterial Agents↗
PubMed1983

Susceptibility testing of Entamoeba histolytica.

The growth of Entamoeba histolytica in microtiter plates in vitro in a variety of environments with reduced oxygen tensions is reported. With 3% O2, 3% CO2, and 94% N2, the parasite growth in microtiter plates was identical to that in screw-capped culture tubes, as measured by [3H]thymidine incorporation and by quantitative parasite counts. There were no significant differences between the drug concentrations necessary to inhibit parasite growth by 50% based on [3H]thymidine incorporation vs those defined by quantitative parasite counts for the 15 antimicrobial agents tested (including seven drugs used for the treatment of amebiasis). This technique provides a reproducible method to quantitate the activity of potential antiamebic agents in vitro. The isotopic method should be of particular value in defining the metabolism of the parasite and effects of antimicrobial agents on it, whereas the morphologic method may be more valuable for workers with limited resources available to them.

Amebicides↗
PubMed1983

Oxygen enhances the antimalarial activity of the imidazoles.

We have previously reported the antimalarial activity of imidazoles and amphotericin B against chloroquine-resistant Plasmodium falciparum. We now report the enhancement of imidazole activity in an atmosphere with 17-18% oxygen (the candle jar) vs. 3% or 0.3% oxygen. Based on both morphologic and radiometric testing, smaller amounts of the imidazoles were required to inhibit parasite growth by 50% in the candle jar vs. 3% or 0.3% oxygen. The use of older (more oxidant-sensitive) red cells also enhanced the antimalarial activity of ketoconazole. Neither increased concentrations of oxygen nor the use of older red cells affected the activity of amphotericin B. These results suggest that the imidazoles may exert their antimalarial effect by increasing the oxidant stress on the red cell-parasite complex.

Amphotericin B↗
PubMed1982

Reinsertability after breast prosthesis pocket infection: an experimental study.

We report the development of an animal model for the study of S. aureus infection in silicone gel-filled prosthesis pockets. The purpose of this study was to determine (1) whether successful reinsertion of a prosthesis into a contaminated pocket requires a finite recovery period between implant removal and reinsertion, and (2) whether parenteral antibiotic treatment affects the success of reinsertion. All infected pockets were lavaged with saline and none were drained, either after wound closure or after implant reinsertion. The results indicate that a delay of 2 or more hours between lavage and reinsertion protects against implant exposure. Therapeutic parenteral antibiotic treatment neither prevented implant exposure nor altered the effect of temporal delay on reinsertion. These studies coupled with recent clinical reports suggest that women who develop breast pocket infection need not wait months for restoration of breast symmetry.

Animals↗
PubMed1982

Lysis of Plasmodium falciparum by ferriprotoporphyrin IX and a chloroquine-ferriprotoporphyrin IX complex.

Ferriprotoporphyrin IX (FP) and a chloroquine-FP complex lysed isolated Plasmodium falciparum parasites as judged by decreases in the turbidity of parasite suspensions and by ultrastructural changes. Exposure of parasite suspensions to 50 microM FP or to a complex formed from 50 microM FP and 20 MicroM chloroquine reduced the number of identifiable parasites and caused swelling and loss of internal detail in those that were identifiable. The amount of lysis was dose-dependent over the range of 10 to 50 microM FP. Formation of a chloroquine-FP complex reduced, but did not eliminate, the toxicity of FP. Since there is evidence indicating that a chloroquine-FP complex forms when chloroquine-susceptible parasites are exposed to chloroquine, we suggest that accumulation of this complex may account for the chemotherapeutic effect of chloroquine against P. falciparum.

Chloroquine↗
PubMed1982

Heparin interferes with the radioenzymatic and homogeneous enzyme immunoassays for aminoglycosides.

Heparin interferes with measurement of aminoglycosides in serum by biological, radioenzymatic, and homogeneous enzyme immunoassay techniques, but not with radioimmunoassay. At concentrations greater than or equal to 10(5) and greater than or equal to 3 X 10(6) USP units/L, respectively, it interferes with the radioenzymatic assay by inhibiting the gentamicin 3-acetyltransferase (EC 2.3.1.60) and kanamycin 6'-acetyltransferase (EC 2.3.1.55) enzymes used in the assay. It interferes with the homogeneous enzyme immunoassays for gentamicin and tobramycin (at concentrations greater than or equal to 10(5) and greater than or equal to 10(4) USP units/L, respectively), but not with the commercially available homogeneous enzyme immunoassays for other drugs. Heparin interference with the homogeneous enzyme immunoassay for aminoglycosides requires both the heparin polyanion and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) bound to a cationic aminoglycoside. This interference can be reproduced with dextran sulfate (but not dextran), and does not occur with free enzyme (glucose-6-phosphate dehydrogenase) alone. We describe how heparin interferes with these two assays and demonstrate interference at heparin concentrations that may be present in intravenous infusions or in seriously underfilled blood-collection tubes.

Amikacin↗
PubMed1981

Sodium polyanethol sulfonate inactivation of aminoglycosides.

Sodium polyanethol sulfonate and another polyanion (dextran sulfate) both inhibited aminoglycoside activity in vitro. This effect was not produced by an otherwise similar neutral carbohydrate (dextran) or by neutral detergents (Brij-35, Triton X-100) but was antagonized by an anion-exchange resin (Dowex 1X8-50). We conclude that the inactivation of aminoglycosides by sodium polyanethol sulfonate results from its polyanionic nature and is unrelated to its detergent properties.

Aminoglycosides↗
PubMed1981

Preliminary identification of mycobacteria isolated from clinical specimens.

From March 1979 to June 1980, we preliminary identified mycobacteria at the time of their initial isolation by colonial morphology, pigmentation, and growth rate. The definitive identifications were predicted accurately for 92% of the mycobacteria isolated from 108 patients. For laboratories that isolate relatively few different species of mycobacteria, the advantages of this approach are its simplicity and the speed with which presumptive identifications can be made available for clinical use.

Bacteriological Techniques↗
PubMed1981

Antibiotic-induced lysis of enterococci.

Enterococci are resistant to penicillin killing in vivo and in vitro. Because some bacteria resistant to penicillin killing have reduced autolytic activity, we examined the lysis of clinical enterococcal isolates suspended in buffer (spontaneous lysis), and compared it with their susceptibility to antibiotic-induced lysis and killing. We found significant correlations between spontaneous and antibiotic-induced lysis, using five antibiotics that inhibit cell wall synthesis (penicillin, cephalothin, bacitracin, cycloserine, and vancomycin). Among isolates, strains more rapidly lysed by one antibiotic were more rapidly lysed by the other antibiotics, and more susceptible to spontaneous lysis. In studies involving a single strain grown in different media, spontaneous lysis also correlated closely with antibiotic-induced lysis. These results are consistent with a common mechanism for spontaneous and antibiotic-induced lysis, such as the autolytic enzyme system. Human serum was one of the least permissive media tested for enterococcal growth and antibiotic-induced lysis and killing. We suggest that the inhibitory effect of human serum on growth and the activation of the enterococcal autolytic enzyme system may be a critical factor in the resistance of enterococcal endocarditis to treatment with penicillin alone.

Anti-Bacterial Agents↗
PubMed1981

Vancomycin therapy in patients with impaired renal function: a nomogram for dosage.

The relation between vancomycin clearance and renal function was studied in 22 patients with various degrees of renal functional impairment and in four normal volunteers. Clearance of vancomycin and creatinine were highly correlated (r = 0.92) among 17 persons not on dialysis. In five dialysis patients vancomycin clearance averaged 0.086 mL/min . kg of body weight (+/- SEM = 0.025). These relations enabled us to construct a nomogram for vancomycin dosage adjustment (based on a mean steady-state serum vancomycin concentration of 15 micrograms/mL) in patients with various degrees of renal functional impairment.

Adolescent↗
PubMed1980

Single-dose kinetics of intravenous vancomycin.

The pharmacokinetic properties of intravenously administered vancomycin were studied in four healthy volunteers. Reversible adverse effects (flushing, tachycardia, pruritus) occurred in two subjects who received high-dose rapid intravenous infusions. Distribution of vancomycin proceeded as a biphasic process in all four subjects. The initial distribution half-life (t1/2 alpha) was less than 8 minutes in all cases, with intermediate half-lives (t1/2 pi) varying from 0.43 to 1.48 hour and elimination half-lives (t1/2 beta) varying from 4.7 to 11.2 hours. Vancomycin clearance was less than creatinine clearance, probably because of serum protein binding, which was determined to be 55 per cent.

Adult↗