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11.  In vitro susceptibility of Campylobacter fetus subsp. jejuni to N-formimidoyl thienamycin, rosaramicin, cefoperazone, and other antimicrobial agents. 
The activities of 11 antimicrobial agents against 36 strains of Campylobacter fetus subsp. jejuni were studied by a broth microdilution method. All strains were susceptible to 7 of the 11 antimicrobial agents. Of the newer agents tested N-formimidoyl thienamycin (MK0787) and rosaramicin had very good activity, whereas cefotaxime, moxalactam, and cefoperazone had poorer activity.
PMCID: PMC181813  PMID: 6459767
12.  Effects of amphotericin B on hepatitis B virus. 
We investigated the effects of amphotericin B (AmB) on the ultrastructure and biochemistry of hepatitis B virus (HBV) and hepatitis B surface antigen (HBsAg) particles. These effects were compared with those reported for AmB and other polyene antibiotics on other lipid-enveloped viruses and artificial membranes. Treatment of HBV particles with concentrations of AmB ranging from 5 to 250 microgram/ml resulted in (i) an increase in HBV deoxyribonucleic acid polymerase activity as the concentration of Amb increased; (ii) changes in the electron microscopic appearance of HBV ranging from increased penetration of negative stain into the lipid envelope to disruption of the virus; and (iii) an increase in density form 1.165 to 1.225 g/ml. In addition, AmB treatment of HBsAg particles resulted in disruption into a nonparticulate HBsAg-reactive fraction and an HBsAg-AmB complex fraction with no HBsAg immunoreactivity.
PMCID: PMC181806  PMID: 7325646
13.  Comparative evaluation of three methods for measuring gentamicin and tobramycin in serum. 
Three procedures (radioimmunoassay, fluorescence immunoassay, and enzyme immunoassay) for the determination of gentamicin and tobramycin levels were compared. These systems were evaluated on the basis of accuracy, reproducibility, specificity, and cost. All three systems showed a high degree of accuracy and precision. The fluorescence immunoassay gave significantly lower values for gentamicin and tobramycin at levels below 5 microgram/ml. Of the three systems, the radioimmunoassay was the least expensive, provided that a minimum of 10 analyses were performed daily; single tests required more technical time and were more costly. Costs of single tests by fluorescence immunoassay and enzyme immunoassay systems were similar. The enzyme immunoassay system performed equally well for both gentamicin and tobramycin in giving rapid and accurate results.
PMCID: PMC181805  PMID: 7034643
14.  Antibiotic action of pyocyanin. 
Biologically produced pyocyanin was purified, and the nature of its antibacterial action was determined for several bacteria. The pigment was shown to be bactericidal for all susceptible organisms. The bactericidal effect was dependent upon pyocyanin concentration and resulted in decreases in viability ranging from 1 to 8 log viable cells ml-1. The gram-positive bacteria were more susceptible as a group to the antibiotic action than were the gram-negative bacteria. All apyocyanogenic pseudomonads tested were totally resistant to the pigment, suggesting that resistance may be a characteristic of the genus. Pseudomonas aeruginosa, the producer organism, was also essentially unaffected by high concentrations of pyocyanin. Facultative anaerobes were twofold or more times resistant to the action of the pigment under fermentative conditions; however, the antibiotic action did not require oxygen since denitrifying bacteria were more susceptible during anaerobic respiration than during aerobic respiration.
PMCID: PMC181804  PMID: 6798928
15.  Amoxicillin-clavulanic acid in treatment of urinary tract infection due to gram-negative bacteria resistant to penicillin. 
Twenty-two adult patients with urinary tract infections caused by penicillin-resistant bacteria completed treatment with amoxicillin alone or amoxicillin plus clavulanic acid in a randomized double-blind clinical trial. Of the 13 patients treated with amoxicillin plus clavulanic acid, the absence of bacteriuria within 7 days of therapy was observed in 85%, as compared with only 25% of the 8 patients receiving amoxicillin only. There were no significant side effects nor any clinical, biochemical, or hematological abnormalities related to either treatment. It was concluded that the combination of clavulanic acid and amoxicillin could be useful in the treatment of uncomplicated urinary tract infection caused by penicillin-resistant bacteria.
PMCID: PMC181801  PMID: 7034642
16.  Influence of serum protein binding and mode of administration on penetration of five cephalosporins into subcutaneous tissue fluid in humans. 
The penetration of five cephalosporins into interstitial fluid was investigated by a new method employing cotton threads implanted subcutaneously. Penetration after short bolus injections, calculated as area under interstitial fluid level curve divided by area under serum level curve x 100, was 47.0% for cephradine, 30.6% for cefuroxime, 26.7% for cefotaxime, 24.6% for cefoxitin, and 9.6% for cefoperazone. There was an inverse correlation between the degree of penetration and serum protein binding with r = -0.97. The area under interstitial fluid level curves was the same whether the drugs were administered as short bolus injections or short time infusions.
PMCID: PMC181798  PMID: 7325644
17.  Cefoxitin pharmacokinetics: relation to three different renal clearance studies in patients with various degrees of renal insufficiency. 
The pharmacokinetics of cefoxitin were examined in 4 healthy volunteers, 6 patients with normal renal function (inulin clearance, greater than 80 ml/min per 1.73 m2), and 35 patients with various degrees of renal insufficiency (inulin clearance, 80 to less than 5 ml/min per 1.73 m2). A single dose of 30 mg of cefoxitin per kg of body weight was injected intravenously over 3 min. Antibiotic concentrations in plasma were determined by the agar diffusion technique. The cefoxitin half-life increased progressively from 39 min in subjects with normal renal function to 23.5 h in oligoanuric patients. Correspondingly, total body clearance decreased from 340 to 13 ml/min per 1.73 m2. In addition to the study of cefoxitin kinetics, in 29 of the 41 patients, three different renal clearance tests were performed (inulin, p-aminohippurate, and creatinine clearances). Of these, p-aminohippurate clearance showed the best correlation with the elimination rate constant beta as well as total body clearance of cefoxitin; but with respect to beta, the differences between the p-aminohippurate and creatinine clearances were quantitatively negligible. Therefore, even in substances which are eliminated predominantly by active tubular secretion, creatinine clearance could be recommended for dosage adjustments.
PMCID: PMC181793  PMID: 7325641
18.  Factors affecting the in vitro activity of cefoperazone against the Bacteroides fragilis group. 
The in vitro activity of cefoperazone against 32 strains of bacteria of the Bacteroides fragilis group was determined on four media by using a variety of test parameters. Lower mean minimal inhibitory concentrations (MICs) were obtained on Mueller-Hinton blood agar and supplemented brain heart infusion agar than were obtained on brucella laked blood agar or Wilkins-Chalgren agar. Higher MICs were obtained with 6-h inocula than with 24-h inocula, and slightly higher MICs were obtained with tests read at 48 as compared with 24 h. Conducting tests in an anaerobic glove box had little effect. The greatest differences in mean MICs were seen with inoculum densities of 10(4) and 10(5) colony-forming units.
PMCID: PMC181789  PMID: 6459765
19.  Comparative activity of mezlocillin, penicillin, ampicillin, carbenicillin, and ticarcillin against gram-positive bacteria and Haemophilus influenzae. 
The in vitro activity of mezlocillin was compared to penicillin G, ampicillin, carbenicillin, and ticarcillin in tests with 195 gram-positive bacteria and 20 Haemophilus influenzae. Against gram-positive isolates excluding enterococci, penicillin was the most active drug, followed by ampicillin, mezlocillin, carbenicillin, and ticarcillin. Ampicillin was the most active of the five drugs against enterococci, whereas mezlocillin was the most active drug against 14 strains of ampicillin-susceptible H. influenzae.
PMCID: PMC181811  PMID: 6459766
20.  Virus inhibition assay for measurement of acyclovir levels in human plasma and urine. 
A simple microplate virus inhibition assay which measures the levels of acyclovir in plasma and urine samples from patients was developed. The assay is based upon the inhibition of the cytopathic effect of herpes simplex virus type 1 on human fibroblast cells. The extent of inhibition of virus cytopathic effect, caused by dilutions of samples from patients, allowed determination of acyclovir concentrations to be made. The assay, which measured biological activity, could detect acyclovir levels of greater than or equal to 1.0 microM. Peak and valley levels measured in plasma samples from two patients were comparable to values obtained by radioimmunoassay. The assay is simple, rapid, and quantitative, and it can be adapted to routine use for a large number of specimens.
PMCID: PMC181799  PMID: 6275786
21.  Effect of carbon dioxide on in vitro susceptibility of anaerobic bacteria to erythromycin. 
The activity of erythromycin against 317 strains of anaerobic bacteria, including 133 strains of the Bacteroides fragilis group, was tested by the agar dilution method in an anaerobic atmosphere with two different concentrations of carbon dioxide and without CO2. The effect of the atmosphere of incubation on the agar surface pH was also determined. All strains grew well in the GasPak (GP) environment. However, 3.5 and 30.3% of strains failed to grow in the 2 and 0% CO2 environments, respectively. The quality of growth was best in the GP environment and poorest in the 0% CO2 environment. Minimal inhibitory concentrations in the GP and 2% CO2 environments were frequently the same or one dilution lower in the 0% than in the GP environment. In the 0% CO2 atmosphere, minimal inhibitory concentrations were usually two to three dilutions lower than in the GP environment. Consequently, only 24% of B. fragilis strains were susceptible to erythromycin in the GP environment, whereas 77% were susceptible in the 0% CO2 environment. For Fusobacterium species, 12% were susceptible to erythromycin in the GP environment, and 73% were susceptible in the 0% CO2 environment. There was a comparable decrease in pH in all three atmospheres tested. In vitro susceptibility testing of erythromycin against anaerobic bacteria should be performed in an atmosphere containing carbon dioxide.
PMCID: PMC181785  PMID: 6798927
22.  Characteristics of rifampin-resistant variants obtained from clinical isolates of Staphylococcus aureus. 
Twenty clinical isolates of Staphylococcus aureus were examined to determine the frequency of rifampin-resistant variants. All isolates were highly susceptible to rifampin, with mean minimum inhibitory concentrations of 0.11 +/- 0.1 microgram/ml and mean minimum bactericidal concentrations of 0.22 +/- 0.2 microgram/ml. The frequency of isolation of resistant variants was similar to all rifampin concentrations tested. Rifampin-resistant variants maintained their resistance upon daily subculture in rifampin-free broth. Rifampin-susceptible S. aureus exhibited a growth and survival advantage over the rifampin-resistant mutants both in pure cultures and in mixtures with rifampin-resistant antecedents. A comparison of the virulence for mice of five susceptible isolates and their 100 microgram/ml-rifampin-resistant variants showed that two of the resistant variants were less virulent than the susceptible strains via intraperitoneal challenge, whereas three of the resistant variants were less virulent by intravenous challenge (P less than 0.05).
PMCID: PMC181786  PMID: 7325636
23.  In vitro antimicrobial activity evaluation of cefodizime (HR221), a new semisynthetic cephalosporin. 
Cefodizime (HR221) is a new alpha-methoxyimino cephalosporin developed by Hoechst-Roussel with a reported serum half-life of over 2 h. In vitro susceptibility studies showed that the cefodizime spectrum includes all those Enterobacteriaceae, staphylococci, Streptococcus spp., Haemophilus spp., and Neisseria spp. normally susceptible to cefotaxime (HR756) or ceftizoxime (FK749) or both. Cefodizime was less active (two- to eightfold) than cefotaxime or ceftizoxime against some enteric species, but was the most potent drug against some strains of Morganella spp. and Proteus vulgaris. Enterococci, methicillin-resistant Staphylococcus aureus, and most Pseudomonas spp. were resistant to cefodizime (median minimum inhibitory concentrations, greater than or equal to 64 microgram/ml). Acinetobacter spp. and Pseudomonas aeruginosa strains required cefodizime concentrations of 32 microgram/ml to inhibit 50% of tested strains. Cefodizime was very stable to hydrolysis by Richmond-Sykes type I, II, III, and IV beta-lactamases, as well as the enzyme derived from Bacillus cereus. The reference PADAC and nitrocefin substrate hydrolysis by a type I beta-lactamase was markedly inhibited (greater than 80%) by cefodizime at concentrations 0.4 to 4% of substrate concentration. Cefodizime was active against 43% of bacteria which were resistant to cephalothin and cefamandole and against 58% of those resistant to aminoglycosides.
PMCID: PMC181795  PMID: 6275785
24.  Laboratory evaluation of the Anderson Technical semiautomated susceptibility testing system. 
Anderson Technical, Inc. has developed rapid, semiautomated equipment for antimicrobial susceptibility testing. A total of 310 fresh clinical bacterial isolates (226 gram-negative and 75 gram-positive) were tested with the Anderson Technical system and compared with those of Micro-Media Systems, Inc. For the gram-positive organisms, 74.3% of the test pairs had identical minimum inhibitory concentration values, whereas 99.1 and 0.9% of the test pairs had minimal inhibitory concentration values differing by less than or equal to 1 and greater than 1 dilution level, respectively. Identical minimum inhibitory concentration values were obtained for 67.2% of the gram-negative test pairs, whereas 97.6 and 2.4% differed by less than or equal to 1 and greater than 1 dilution level, respectively. For all organisms tested, 98.0% differed by less than or equal to 1 dilution level. The Anderson Technical equipment proved to be a rapid and flexible system for microdilution testing.
PMCID: PMC181797  PMID: 7325643
25.  Susceptibility of Clostridium septicum to 23 Antimicrobial Agents 
The in vitro susceptibility of Clostridium septicum was studied with a microtiter broth dilution method. Several antimicrobial agents demonstrated consistently good activity against the organism.
PMCID: PMC181814  PMID: 7325648

Results 1-25 (390)