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Biomedical subjects

R E Bryant

Publications and source records attributed to R E Bryant.

At least 19 recordsLinked to original sources
PubMed1992

Beta-lactam enhancement of aminoglycoside activity under conditions of reduced pH and oxygen tension that may exist in infected tissues.

Aminoglycoside activity is suppressed under conditions of low pH and oxygen tension that are likely to occur in infected tissues; the suppressive effects of these conditions are additive. Under aerobic conditions, the MIC of amikacin for 10 isolates of Escherichia coli was 4.8 +/- 0.7 micrograms/ml at pH 7.2 and increased to 40.0 +/- 8.2 micrograms/ml at pH 6.0. Under anaerobic conditions, the MIC of amikacin for E. coli was 30.0 +/- 1.5 micrograms/ml at pH 7.2 and greater than 50.0 micrograms/ml at pH 6.0. In vitro and in vivo studies of amikacin activity in an acidic and hypoxic milieu containing beta-lactamase demonstrated substantially enhanced bactericidal activity when amikacin and beta-lactams were used together. Under conditions of reduced pH and oxygen tension, cefotaxime enhanced [3H]-tobramycin uptake by E. coli 14-fold and [3H]amikacin uptake 7-fold and appeared to overcome the suppressive effect of those conditions on uptake of aminoglycosides by bacteria.

Abscess↗
PubMed1989

Effect of the abscess environment on the antimicrobial activity of ciprofloxacin.

The present studies were conducted to identify factors in human purulent material that might limit or enhance the activity of ciprofloxacin against bacteria causing suppurative infection. Ciprofloxacin, imipenem, and ampicillin were tested with regard to binding or inactivation by pus. The bactericidal activity of ciprofloxacin and imipenem were tested against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, or Staphylococcus aureus in human pus with a pH of 6.0 incubated at 37 degrees C under aerobic or anaerobic conditions. The effect of single or combination drug therapy with 20 mg/kg of ciprofloxacin, imipenem, or rifampin given every 12 hours was tested against E. coli or P. aeruginosa in polymicrobic murine abscesses that had been produced by subcutaneous injection of either of those organisms mixed with Bacteroides fragilis and autoclaved human stool. Antibiotic levels and the number of bacteria surviving in pus were quantitated. Therapy of subcutaneous abscesses was delayed 72 hours to test drug efficacy against organisms in well-established infections. Levels of ampicillin, imipenem, or ciprofloxacin were reduced from 10 micrograms/ml to 3.1 +/- 4.0, 2.7 +/- 3, or 5.8 +/- 2 micrograms/ml, respectively, after incubation in eight pus specimens for 24 hours at 37 degrees C. Ampicillin levels were reduced to less than 1 microgram/ml in four pus specimens containing beta-lactamase. Imipenem levels were undetectable in two specimens and were 0.2 micrograms/ml in one specimen. Ciprofloxacin binding to pus supernate or sediment appeared to be explained by its binding to the deoxyribonucleic acid (DNA) present in pus. Activity of 5 micrograms/ml of ciprofloxacin against four E. coli or K. pneumoniae strains in pus in vitro was greater than that of twofold higher concentrations of imipenem. The bactericidal activity of ciprofloxacin and imipenem were comparable but substantially reduced against S. aureus and P. aeruginosa in pus. Ciprofloxacin alone or regimens combining ciprofloxacin with rifampin or rifampin plus imipenem reduced the number of E. coli in polymicrobic subcutaneous abscesses but had little effect on P. aeruginosa in polymicrobic abscesses. The anaerobic abscess milieu appeared to inhibit the growth of P. aeruginosa. Ciprofloxacin activity in abscess fluid did not appear to be adversely affected by acid pH, aerobic or anaerobic conditions of incubation, the abscess constituents, or the binding of ciprofloxacin to the DNA in pus. Ciprofloxacin was bound to DNA of bacterial or human origin. Binding by pus was reversible, and binding to DNA extracts of pus was blocked by pretreatment of extracts with deoxyribonuclease but not by pretreatment with ribonuclease.(ABSTRACT TRUNCATED AT 400 WORDS)

Abscess↗
PubMed1988

Chronic hyperdynamic sepsis in the rat: I. Characterization of the animal model.

We describe a new rat model of chronic hyperdynamic sepsis. After control values for weight gain, and food and water intake of each animal were obtained over a 5-day period, male Sprague-Dawley rats weighing 370-425 g were anesthetized, catheterized to allow chronic cardiac-output measurements, and a sterile subcutaneous cavity was formed over the flank area. The animals were allowed a 3-4 day postoperative recovery period. Body weight, food and water intake, and cardiac output were measured daily. Frequent blood samples were withdrawn for bacterial cultures and white cell counts (WBC). On the third and, in some cases, the fourth postoperative day, the subcutaneous cavity was inoculated with 10(9) colony-forming units of Escherichia coli and Bacteroides fragilis. The resulting sepsis was characterized by loss of body weight in spite of normal food and water intake, increased cardiac output, increased WBC, intermittent bacteremia, decreased muscle mass, and decreased cross-sectional area of skeletal muscle myofibrils. Two levels of septic response emerged--moderate and severe. Based on the above-mentioned measurements, it was possible to categorize all long-term septic animals into these two groups. Both groups exhibited cardiac-output, body-weight, and WBC data significantly different from sham controls. Repeated inoculations of the subcutaneous abscess initiated on the third postoperative day resulted in moderate sepsis with no long-term mortality, severe sepsis with 23% mortality over a 3-week period, or a 100% mortality within 4 days, depending on the virulence of the E. coli organisms used. The new model is ideally suited for pathophysiologic studies of sustained, hyperdynamic sepsis.

Animals↗
PubMed1987

Effect of abscess milieu on bactericidal activity of LY146032 against staphylococci.

The antistaphylococcal activity of LY146032 was tested in human pus in vitro and in a murine abscess model in vivo. The drug was not degraded by pus containing beta-lactamase and had equally good or better activity than nafcillin or vancomycin against Staphylococcus aureus or Staphylococcus epidermidis in vitro and in vivo. Its activity was slightly enhanced when used in combination with rifampin and tobramycin.

Abscess↗
PubMed1987

Oral ciprofloxacin in refractory gram-negative bacillary infections.

The 13 patients included in this series: had chronic Gram-negative bacillary infections that were refractory to prior antibiotic therapy; were unable or unwilling to receive intravenous antibiotics; and had altered host defenses or environmental factors that contributed to persistent infection. Five patients had chronic polymicrobic Gram-negative osteomyelitis, three had urinary tract infections caused by Pseudomonas aeruginosa, two had Pseudomonas skin infections and three had respiratory tract infections with Gram-negative bacilli. The overall bacteriological cure rate for Gram-negative bacilli was four of five osteomyelitis, all three urinary tract infections, both skin infections and one out of three respiratory infections. Secondary infections occurred in two patients with bone infections, one with prostatitis and one with deep seated cellulitis and myonecrosis. Two patients with end-stage lung disease had emergence of resistant strains during therapy. Ciprofloxacin was well tolerated and effective in most of the ambulatory patients with refractory Gram-negative bacillary infection. It appears to be especially promising for Pseudomonas infections of the bone, urinary tract and soft tissue.

Adult↗
PubMed1985

Prosthetic valve endocarditis caused by Staphylococcus epidermidis. Development of rifampin resistance during vancomycin and rifampin therapy.

Development of rifampin-resistant Staphylococcus epidermidis was documented in three patients receiving vancomycin and rifampin therapy for prosthetic valve endocarditis. The minimum inhibitory concentrations and minimum bactericidal concentrations of rifampin for the original three isolates were 0.4 micrograms/mL or less. Organisms cultured during relapse or prosthetic valve replacement had minimum inhibitory concentrations of rifampin that were 12.5, 50, and greater than 100 micrograms/mL, respectively. Surgical intervention was necessary in all patients. One died, and one required a second prosthetic valve placement. The patients were treated with vancomycin plus aminoglycoside following identification of rifampin resistance. These observations suggest that vancomycin and rifampin may not be adequate therapy for prosthetic valve endocarditis caused by S epidermidis.

Drug Resistance, Microbial↗
PubMed1983

Endotoxin contamination of enzyme conjugates used in enzyme-linked immunosorbent assays.

The specificity of the enzyme-linked immunosorbent assay(s) is thought to depend on the specificity of the antibody used in the assay system. Therefore, the association of broadly reactive antigens like endotoxin with enzyme conjugates or other enzyme-linked immunosorbent assay reagents has the potential of altering the specificity of reactions in the enzyme-linked immunosorbent assay. Using the Limulus amoebocyte lysate assay, we demonstrated that commercially prepared conjugates of goat anti-human immunoglobulin G peroxidase, goat anti-rabbit immunoglobulin G alkaline phosphatase, rabbit anti-human immunoglobulin G, and other enzyme conjugates contained endotoxin. Furthermore, the staphylococcal protein A, horseradish peroxidase, and bovine alkaline phosphatase used to prepare enzyme conjugates also contained endotoxin. Commercially obtained bovine alkaline phosphatase contained as much as 1.0 microgram of endotoxin per ml of enzyme solution. Both commercially prepared enzyme conjugates and those prepared by us contained endotoxin as determined by their absorption to immobilized monoclonal antibody to lipid A or to immobilized Limulus amoebocyte lysate. The results of this study further suggest that the endotoxin was associated with the enzyme component of the conjugate. In a competitive inhibition enzyme immunoassay, 10 micrograms of lipid A per ml inhibited binding of the enzyme conjugate to adsorbed Limulus amoebocyte lysate, thereby confirming that endotoxin mediated the binding of the conjugate in that system. The potential significance of endotoxin bound to enzyme conjugates may be far reaching because of the ubiquity of endotoxin in conjugates and the prevalence of antibodies to endotoxin in mammalian serum.

Alkaline Phosphatase↗
PubMed1982

Depletion and recovery of ATP in V79 cells with exposure to inhibitors of glycolysis and oxidative phosphorylation.

Cells of the cultured hamster cell line V79 were labeled with tritiated adenosine and incubated for up to 30 min in the presence of inhibitors of glycolysis and oxidative phosphorylation. These inhibitors were (a) 5 mM KCN plus 5 mM iodoacetate, (b) 5 mM KCN plus 5 mM KF, and (c) 15 mM KCN plus 15 mM KF. The fate of the tritium label was examined during incubation with inhibitors and also during subsequent incubation in growth medium in the absence of inhibitors. The tritiated ATP pool was found to decrease in cells incubated in the presence of any of the inhibitor combinations, but only in the presence of 15 mM KCN plus 15 mM KF was this pool decreased below the level of detection. After cells were incubated with KCN plus KF, a high level of ATP was recovered when the inhibitors were removed. Cells incubated with KCN plus iodoacetate retained depletion levels of ATP. Plating efficiency and trypan blue staining showed that KCN-KF treated cells retained viability, whereas KCN-iodoacetate treated cells did not. Cells were examined for ability to take up tritiated uridine before, during, and after depletion of ATP by incubation in the presence of 15 mM KCN plus 15 mM KF. These cells were found to have a variation in uridine uptake that was related directly to intracellular ATP level. Cells in which the ATP was very low exhibited little or no uridine uptake, whereas cells in which the ATP level was near normal exhibited normal uridine uptake.

Adenosine Triphosphate↗
PubMed1982

Chemoprophylaxis in cardiac and orthopedic surgery: comparison of cephalothin and cephapirin.

In a retrospective sequential study we determined the rate of infection occurring despite cephalothin or cephapirin chemoprophylaxis in orthopedic and cardiac surgery done from 1973 to 1977. The incidence of infection after prosthetic hip placement or open reduction of hip fracture was 3.4% and 1.0% in patients receiving cephalothin or cephapirin, respectively. The infection rate after prosthetic heart valve implantation was 3.5% in those receiving cephalothin and 1.6% in those receiving cephapirin. There was no significant difference in infection rate, duration of fever greater than or equal to 38.0 C, or length of postoperative hospitalization. The efficacy of selected antistaphylococcal antibiotics in preventing colonization of human fibrin clots by staphylococci was studied. Although cephapirin was effective at lower concentration, the activity of cephalothin and cephapirin was comparable. Cephalothin and cephapirin have equivalent chemoprophylactic activity by clinical and microbiological criteria, permitting cost to be used as a basis for choosing between these antibiotics.

Cardiac Surgical Procedures↗
PubMed1981

Acid-base changes and acetate metabolism during routine and high-efficiency hemodialysis in children.

Changes in acid-base status and plasma acetate concentrations were studied in eight children during 11 hemodialysis sessions. During dialysis, the blood bicarbonate concentration fell (20.5 +/- 0.7 to 19.6 +/- 0.8 mEq/liter), the Pco2 fell (33.4 +/- 0.8 to 27.5 +/- 1.4 mm Hg), and the pH rose (7.42 +/- 0.01 to 7.48 +/- 0.02). During the hour after dialysis, the bicarbonate concentration rose to normal (23.4 +/- 0.7 mEq/liter), the PCO2 rose (32.8 +/- 0.8 mm Hg), and the pH remained unchanged. The half-life of plasma acetate, measured after dialysis, was 8.7 min. During five "high-efficiency" dialysis sessions (urea clearance, greater than 3.0 ml/min/kg), blood bicarbonate concentration fell 3.2 mEq/liter, PCO2 fell 8.7 mm Hg, and plasma acetate rose to 7.51 mmoles/liter, whereas during six "routine efficiency" dialysis sessions (urea clearance. 1.5 to 3.0 ml/min/kg), blood bicarbonate rose 1.0 mEq/liter, PCO2 fell 36 mm Hg, and plasma acetate rose to 3.52 mmoles/liter. At 1 hour after the end of dialysis, blood bicarbonate, PCO2, and plasma acetate concentrations were similar in the two groups. Clinical problems occurred more frequently in the high-efficiency group during dialysis although the difference was not significant. The data indicate that (1) dialysis with acetate buffer effectively corrects predialysis metabolic acidosis, (2) although children have a high rate of acetate metabolism, during high-efficiency dialysis this rate is exceeded by the influx of acetate, and acid-base abnormalities occur. These abnormalities are transient but may cause clinical problems.

Acetates↗
PubMed1980

beta-Lactamase activity in human pus.

Pus was obtained from patients with polymicrobial intraabdominal abscesses or polymicrobial empyema. Physical and chemical characteristics of 12 specimens were examined, and bacterial isolates were enumerated. Pus supernatant of six specimens rapidly inactivated penicillin, cephalothin, and cefazolin. Carbenicillin and ticarcillin were similarly degraded by supernatant of certain pus specimens. Cefoxitin, chloramphenicol, and clindamycin were not appreciably inactivated by pus supernatant. Degradation of penicillin and cephalosporin congeners in pus was due to the presence of beta-lactamase, as shown by chemical interaction with nitrocefin, chromatography, and inhibition by the beta-lactamase inhibitor clavulanic acid. Pus supernatant containing beta-lactamase activity reduced the bactericidal activity of carbenicillin against Bacteroides fragilis in whole pus in an abscess model in vitro. Bactericidal activity of clindamycin or cefoxitin was not impaired in pus containing beta-lactamase.

Bacteroides fragilis↗
PubMed1980

Herpes simplex type 1 hepatitis in renal transplantation.

Herpes simplex is a rare but usually fatal cause of acute hepatitis in adults. Most previously reported cases have occurred in debilitated or immunosuppressed patients. We report two additional fatal cases that occurred in renal transplant recipients. In case 1, there is evidence that the allograft may have been the initial nidus of infection. In case 2, dissemination from a genital infection occurred and failed to respond to vidarabine therapy that was started early in the clinical course. We also review the literature concerning previously reported cases of herpes hepatitis.

Adult↗
PubMed1977

Properties of an altered RNA polymerase II activity from an alpha-amanitin-resistant mouse cell line.

alpha-Amanitin-resistant clones were selected in the mouse lymphoblastoid cell line L5178Y. One resistant clone, named A169b, was recloned and the properties of its DNA-dependent RNA polymerases were examined. The RNA polymerase II activity from A169b differs from the parental cell line in that approximately half the activity is resistant to 0.5 microgram/mL alpha-amanitin, while the parental enzyme is 50% inhibited at 0.005 microgram/mL. The enzymes from A169b and the parental line were purified free of polymerase III and their properties compared. The two preparations were identical in their apparent affinities for the four nucleoside triphosphates, in their salt and divalent cation preferences, and in their preference for denatured over native DNA. They differed in their response to alpha-amanitin. The apparent K1 for the parental enzyme was 3.5 X 10(-9) M; plots of 1/V vs. alpha-amanitin concentration gave a biphasic curve with A169b enzyme. The two apparent K1 values were 4.1 X 10(-9) and 2.1 X 10(-6) M. In addition, the enzyme from A169b showed a twofold higher activity on poly [d(AT)] as template, compared to native DNA, than that of the parental enzyme. Other template preferences may be affected, but differences were marginal. These results indicate that mutation to alpha-amanitin resistance may alter other enzymatic parameters; such mutations may be helpful in elucidating structure-function relationships in these complex enzymes.

Amanitins↗
PubMed1977

Unsuccessful treatment of staphylococcal endocarditis with cefazolin.

Two patients with staphylococcal endocarditis were treated unsuccessfully with cefazolin sodium. One patient relapsed after 52 days of therapy. The second patient had concomitant central nervous system infection and failed to respond to cefazolin therapy. Both patients recovered with methicillin sodium or nafcillin sodium therapy. Other studies report unsuccessful therapy of staphylococcal endocarditis with cefazolin.

Adult↗
PubMed1977

Comparison of pharmacological and antimicrobial properties of cefadroxil and cephalexin.

Pharmacological and antimicrobial properties of cefadroxil, a new cephalosporin antibiotic, were compared with cephalexin. Absorption and excretion were studied in 20 healthy men. Peak concentrations of the drugs in serum were similar after ingestion of single 500-mg tablets. The concentration of cefadroxil in serum was more sustained than that of cephalexin. Levels of cefadroxil in serum after a dose of 1,000 mg were approximately twice those after a 500-mg dose through 6 h. Each drug administered in a dose of 500 mg every 6 h for 24 h resulted in concentrations in serum that were similar to a single dose without accumulation. Ninety-three percent of the cefadroxil and 85% of the cephalexin were excreted in urine after ingestions of single 500-mg tablets. The urine concentration of cefadroxil was more sustained than cephalexin. Minimal inhibitory and minimal bactericidal concentrations for clinical isolates were comparable with each drug. Cefadroxil compares favorably with cephalexin in this study. Sustained levels of cefadroxil in serum and urine suggest that this drug may be given at less frequent intervals than cephalexin.

Adult↗
PubMed1975

Gram-negative bacillary endocarditis. Interpretation of the serum bactericial test.

Although the serum bactericidal test is commonly used in the management of infective endocarditis, little has been written about its validity or limitations. We report three cases of gram-negative bacillary endocarditis (Pseudomonas aeruginosa, Vibrio fetus and Serratia marcescens) encountered in 1 year at a Veterans Administration hospital. Serum bactericidal titers were considered necessary to identify inadequate antibiotic regimens or to avoid unnecessary drug toxicity. The limitations of the test, particularly those pertaining to gram-negative infections, are reviewed. Misleading results during treatment with aminoglycoside antibiotics could be due to the tendency of serum to become alkaline on standing. A detailed study of the interaction of the complement-dependent bactericidal system of serum with eight antibiotics is presented. In the context of the serum bactericidal test, the interaction was additive or synergistic in 15 of 16 determinations, indicating the need to include a control study of serum sensitivity of the infecting microorganism in each case.

Adult↗