The antimicrobial activity of vancomycin in the presence and absence of sodium carboxymethyl starch.

The purpose of this work was to determine any effects the presence of sodium carboxymethyl starch may have on the antimicrobial activity of vancomycin given a previously described interaction between vancomycin and sodium carboxymethyl starch. In particular, the in-vitro activity of vancomycin against two clinically relevant bacteria, Staphylococcus aureus and Enterococcus faecalis, was studied in the presence of varying concentrations of sodium carboxymethyl starch. From two independent studies conducted using an agar dilution method, it appeared that the binding of vancomycin to sodium carboxymethyl starch had no effect on the in-vitro antimicrobial activity of vancomycin. The minimum inhibitory concentration of vancomycin against S. aureus in the presence of as much as 1 mg mL(-1) sodium carboxymethyl starch was similar to that of the control where no sodium carboxymethyl starch was added (1-4 microg mL(-1) vs 1-2 microg mL(-1), respectively). Likewise, the minimum inhibitory concentration of vancomycin against E. faecalis in the presence of 1 mg mL(-1) sodium carboxymethyl starch was also similar to that of the control where no sodium carboxymethyl starch was added (1-4 microg mL(-1) vs 1-4 microg mL(-1), respectively). However, there may be factors in the in-vitro method, such as high ionic strength, that could disrupt the interaction between vancomycin and sodium carboxymethyl starch. Therefore, the possibility of diminished vancomycin activity in-vivo cannot be ruled out. A small percentage (8-10%) of vancomycin was determined to be bound to sodium carboxymethyl starch in broth media. Given these results, the impact of sodium carboxymethyl starch on the in-vitro antimicrobial activity of vancomycin is expected to be minimal. Binding studies could not be conducted with gelled agar due to its semi-solid state.

In vitro antimicrobial activity of the thiazolyl peptide antibiotic MDL 62,879 (GE2270 A).

Compound MDL 62,879 (GE2270 A) is a thiazolyl peptide antibiotic that appears to inhibit aminoacyl-tRNA binding to elongation factor Tu. In the present study, it was shown that MDL 62,879 broth microdilution MIC values were generally 2-4 doubling dilutions lower in the presence of 0.02% bovine serum albumin. Using US clinical isolates and BSA-supplemented media, MDL 62,879 was more active than teicoplanin and vancomycin against the staphylococci and glycopeptide-resistant and glycopeptide-susceptible enterococci and equally active against the streptococci. Broth microdilutions MIC values were not appreciably affected by inoculum concentrations of 5 x 10(4) to 5 x 10(8) cfu/ml or in the presence of 3.5% human serum albumin.

Comparison of biological and chemical assays for the quantitation of rifapentine in human plasma.

The purpose of this study was to establish the correlation between biological and chemical assays for the quantification of rifapentine in human plasma. The bioassay was found to overestimate antibiotic plasma concentration when compared to the high-performance liquid chromatography (HPLC) assay for rifapentine (r = 0.9538, n = 220). This was because of the presence of varying amounts of the biologically active 25-O-desacetyl metabolite in the test samples. A better correlation (r = 0.9804, n = 220) was observed when the bioassay data were compared to combined parent-metabolite HPLC values. Such correlative data are necessary adjuncts in the establishment of antibiotic susceptibility test breakpoints.

In vitro activity of the semisynthetic glycopeptide amide MDL 63,246.

The in vitro activity of the semisynthetic glycopeptide amide MDL 63,246 against 293 U.S. clinical isolates of gram-positive cocci was determined by the broth microdilution method. When compared with teicoplanin, MDL 63,246 had improved activity against Staphylococcus epidermidis (MICs that inhibited 90% strains tested [MIC90s], 0.25 versus 8 micrograms/ml, respectively). Staphylococcus haemolyticus (MIC90s, 1 versus 32 micrograms/ml, respectively), and VanA Enterococcus faecium (MIC90s, 32 versus > or = 1,024 micrograms/ml, respectively).

Comparison of agar dilution, tube dilution, and broth microdilution susceptibility tests for determination of ramoplanin MICs.

Standard broth microdilution (with and without bovine serum albumin [BSA] supplementation), tube dilution, and agar dilution susceptibility tests were compared for determining ramoplanin MICs. With a data base of 246 clinical isolates of gram-positive bacteria from 33 U.S. sites, it was shown that (i) agar and tube dilution susceptibility tests gave essentially the same results (93.9% of the test results were within 1 doubling dilution of equivalence), (ii) broth microdilution susceptibility tests gave results up to 5 doubling dilutions higher than agar or tube assays, and (iii) this data skewing could be reversed by BSA supplementation (final concentration, 0.02%) of the broth microdilution test medium.

Bioassay quantitation of ramoplanin in human and in nonprimate sera.

This study developed and validated a bioassay for ramoplanin in human, dog, rabbit, and rat sera. Mean analyte recoveries and coefficients of variation for duplicate assays with each serum using coded and spiked (30-720 ng/ml) samples ranged from 93.5% to 106.3% and from 1.8% to 5.4% respectively. All correlation coefficients were > 0.99 and, for each serum, there was no significant difference in overall analyte recovery between the 2 test days.

A time-course study of airway hyperresponsiveness in conscious parainfluenza virus type 3-infected guinea pigs.

The study of virus-induced airway hyperresponsiveness may provide insight into mechanisms that contribute to respiratory diseases such as asthma. We examined changes induced by parainfluenza virus type 3 (PI-3) in lung lesions, tissue weights, and airway responsiveness to aerosols of histamine, methacholine, or citric acid in conscious guinea pigs, using modified whole body plethysmography. During the first week after inoculation, infected lung tissue had peribronchiolitis and airway hyperresponsiveness to various agents when dyspnea and significant respiratory events were measured; these effects persisted throughout postinoculation weeks 2 and 3. Airway hyperresponsiveness was defined by reductions in the onset of dyspnea or significant respiratory events. Throughout the course of the study, PI-3 infected animals had resting respiratory patterns that reflected labored breathing and may have been related to the edema indicated by increased lung weights. Furthermore, increased numbers of inflammatory cells were observed in lung tissue as well as bronchoalveolar lavage fluid of infected animals at these times. Unlike PI-3 infection, exposure to gram-negative endotoxin resulted primarily in airway hyporesponsiveness to histamine aerosol. Hence, we have shown PI-3 infection in guinea pigs causes time-dependent alterations in airway responsiveness to diverse bronchoactive agents as well as in normal breathing patterns, which may persist up to several weeks after inoculation in animals that may otherwise appear normal.

Effect of protein on ramoplanin broth microdilution minimum inhibitory concentrations.

Ramoplanin is a glycolipodepsipeptide antibiotic active against Gram-positive bacteria. We observed that microdilution minimum inhibitory concentrations (MICs) were higher than those obtained in glass tubes or by agar dilution. Initial studies showed that these differences disappeared when 30% bovine serum was added to the broth. Further studies showed that addition of 0.01% bovine serum albumin (BSA) to the broth lowered the microdilution MICs for staphylococci, streptococci, and enterococci by four- to 32-fold. This phenomenon occurred in several commonly used growth media and in different types of commercially available microtiter trays. Precoating of the microtiter wells with a dilute solution of BSA (0.02%) had the same effect. It seems likely that ramoplanin adsorbs to plastic surfaces and is lost from solution, and that protein masks the sites of adsorption. Ramoplanin MICs may be reliably determined by broth microdilution if a small amount of protein is added to the diluent.

Applicability of teicoplanin dosage adjustment guidelines for renally impaired patients over the range of 3 to 30 mg kg-1.

The pharmacokinetics of teicoplanin were investigated in 13 subjects with various degrees of renal impairment using a randomized two-period crossover design; 11 subjects completed both periods. Doses of 3 and 30 mg kg-1 were administered as single dose, 60-min constant rate intravenous infusions. Blood samples were obtained over 28 days and urine was collected over 48 h. Serum and urine were analyzed using a microbiological assay. As previously observed in studies conducted in renally impaired subjects, teicoplanin total and renal clearance significantly decreased with decreasing creatinine clearance (p < 0.0001). However, for these parameters, no differences between doses were observed. Dosage adjustment guidelines for renally impaired patients are usually developed using the ratio of total clearance in renally impaired patients to the total clearance in patients with normal renal function. Since no dose-related differences existed in the relationship between teicoplanin total clearance and creatinine clearance, initial dosage adjustment guidelines for renally impaired patients developed at 3 or 30 mg kg-1 are applicable over the range of 3 to 30 mg kg-1.

Evaluation of the teicoplanin broth microdilution and disk diffusion susceptibility tests and recommended interpretive criteria.

Comparative teicoplanin in vitro susceptibility data were generated for 1201 Gram-positive US clinical trial isolates using standardized broth microdilution and disk diffusion techniques. Based on the results of this study, the following interpretive criteria for teicoplanin are recommended: for MIC tests, less than or equal to 8 micrograms/ml = susceptible, 16 micrograms/ml = moderately susceptible, and greater than or equal to 32 micrograms/ml = resistant; and for disk (30 micrograms) tests, greater than or equal to 14 mm = susceptible, 11-13 mm = intermediate, and less than or equal to 10 mm = resistant.

Pharmacokinetics of teicoplanin upon multiple dose intravenous administration to normal healthy male volunteers.

Teicoplanin pharmacokinetics were investigated upon multiple dose intravenous administration of 6 and 12 mg kg-1 in 10 normal, healthy, male volunteers, using a two-period, randomized, crossover design; six subjects completed both periods. On day 1, 6 or 12 mg kg-1 was administered every 12 h as a 30-min constant rate intravenous infusion (two doses). Starting on day 2, the same dose (6 or 12 mg kg-1) was administered every 24 h for an additional 13 days. Blood and urine samples were collected over 21 days. Serum and urine were analyzed using a microbiological assay. Following a minimum of 3 weeks after completion of the first period, subjects were crossed over to the other dose. Following multiple dose intravenous administration of 6 and 12 mg kg-1, median pharmacokinetic parameters included: steady-state volume of distribution of 1.4 and 1.2 l kg-1; total clearance of 12.2 and 14.0 ml h-1 kg-1; renal clearance of 11.1 and 10.3 ml h-1 kg-1; and terminal disposition half-life of 159 and 155 h, respectively. No statistically significant dose-related difference was observed. In addition, a cross-study comparison further supports dose proportionality of teicoplanin upon multiple dose intravenous administration of 3 to 12 mg kg-1.

beta-Lactam antibiotic modulation of murine neutrophil cytokinesis.

Fourteen cephalosporins, 11 penicillins and 1 monobactam were evaluated for their in vitro modulation of murine neutrophil cytokinesis. As a result, the beta-lactam antibiotics were placed into 6 groups based on their effect on random (R) and FMLP-directed (D) migration [Group 1 (no effect): cephalosporin C; Group 2 (R-->D decreases): cloxacillin, cefotaxime, ceftazadime, cefuroxime, cephalothin, cephapirin, cephadine, nafcillin, piperacillin, ticarcillin, ampicillin, oxacillin, aztreonam; Group 3 (R increases D-->): cephaloridine; Group 4 (R increases D increases): cefsulodin; Group 5 (R increases D decreases): cefoperazone, cefoxitin, ceftriaxone, 6-amino-penicillanic acid; Group 6 (R decreases D decreases): cefadroxil, cefazolin, penicillin G, methicillin]. Trypan blue exclusion studies showed that inhibition of R and D by Group 6 beta-lactam antibiotics is not due to overt cytotoxicity. beta-lactam antibiotics inhibiting D also increased neutrophil adherence to plastic at a concentration of 1000 microM. Finally, the [Ca++] inhibitor chlorpromazine significantly abrogates beta-lactam- and FMLP-directed migration at a test concentration of 1 microM.

Pharmacokinetics of teicoplanin upon multiple-dose intravenous administration of 3, 12, and 30 milligrams per kilogram of body weight to healthy male volunteers.

Teicoplanin pharmacokinetics were evaluated after multiple-dose intravenous administration to healthy male volunteers by using a randomized, double-blind, parallel design. Doses of 3, 12, or 30 mg of teicoplanin per kg of body weight were administered every 24 h for 14 days as 60-min constant-rate intravenous infusions. Blood and urine samples were collected over 21 days and analyzed by a microbiological assay. Twenty-three subjects were included in the pharmacokinetic analysis. The median pharmacokinetic parameters upon multiple-dose intravenous administration of 3, 12, and 30 mg/kg included steady-state volumes of distribution of 0.94, 0.77, and 0.68 liter/kg; total clearances of 11.9, 12.0, and 13.2 ml/h/kg; and terminal disposition half-lives of 143, 166, and 96 h, respectively. Renal clearance accounted for approximately 95% of total clearance. No dose-related differences existed for teicoplanin total or renal clearance. The steady-state volume of distribution decreased significantly with increasing doses. As a result of the decrease in the volume of distribution, the terminal disposition half-life at 30 mg/kg was significantly decreased. However, the decreases in the volume of distribution and terminal disposition half-life are of limited clinical importance, since steady-state trough concentrations in serum increase in proportion to dose. Combined results of all multiple-dose studies with similar durations of sample collection indicate no dose-related differences for any pharmacokinetic parameters from 3 to 12 mg/kg. As observed in the present study, no dose-related differences exist for teicoplanin total and renal clearances from 3 to 30 mg/kg. However, at 30 mg/kg, a significant decrease in the steady-state volume of distribution is observed. As a consequence of the reduction in the volume of distribution at 30 mg/kg with no change in clearance, the terminal disposition half-life is decreased.

Teicoplanin measurement in patients with renal failure: comparison of fluorescence polarization immunoassay, microbiological assay, and high-performance liquid chromatographic assay.

Characterization of antibiotic pharmacokinetics in patients with renal insufficiency may be complicated by interfering substances within the assay. We compared three different assays for teicoplanin in serum and dialysate of 10 hemodialysis and six continuous ambulatory peritoneal dialysis (CAPD) patients. The microbiological assay (micro) had a within-run and between-run coefficient of variation (% CV) of less than 7.5% for concentrations ranging from 0.2 to 96 micrograms/ml. The high-performance liquid chromatographic assay (HPLC) within- and between-run %CV was less than 8% for concentrations ranging from 1 to 80 micrograms/ml. The fluorescence polarization immunoassay (FPIA) within- and between-run %CV was less than 7% for concentrations ranging from 5 to 100 micrograms/ml. In serum of hemodialysis patients FPIA results were slightly higher than HPLC results: FPIA = 1.11 HPLC + 2.37 (r = 0.975, n = 202), and FPIA concentrations in serum were also slightly higher than those measured by micro (FPIA = 1.21 micro - 1.57, r = 0.972, n = 161). The HPLC and micro serum results were also comparable in hemodialysis patients: micro = 0.92 HPLC + 2.89, r = 0.953, n = 160. However, in CAPD patients micro results were lower than HPLC results in serum (micro = 0.82 HPLC + 0.49, r = 0.981, n = 262). In peritoneal dialysate, HPLC values were approximately 60% of the micro values. Thus, FPIA may be the optimal technique for therapeutic monitoring of teicoplanin in the clinical setting due to its simplicity, specificity, and good correlation to HPLC and micro.

Comparative therapeutic efficacy of teicoplanin and vancomycin in normal and in neutropenic mice infected with Staphylococcus haemolyticus.

This study describes the evaluation of a murine bacteraemia model for assessing antibiotic efficacy in normal and neutropenic mice infected with coagulase-negative staphylococci. In one such evaluation, it was found that there was no significant (P greater than 0.05) difference in the ability of teicoplanin or vancomycin to protect normal or neutropenic CD-1 mice, lethally-infected with Staphylococcus haemolyticus. However, about a four-fold increase of either antibiotic was needed to protect the immunocompromised animals.

Pharmacokinetics and bioavailability of a new formulation of teicoplanin following intravenous and intramuscular administration to humans.

Pharmacokinetics, bioavailability, and local tolerance (at the site of intramuscular administration) of a new formulation of teicoplanin (400 mg/3 mL) were investigated in 24 normal, healthy, male volunteers. A single dose of 6 mg/kg was administered intravenously and intramuscularly using a randomized crossover design. Volunteers and investigator were blinded as to the route of administration; placebo was administered by the other route. Blood and urine samples were collected for 21 days and were analyzed for microbiological activity. The median (range) pharmacokinetic parameters of teicoplanin following single-dose iv administration were as follows: steady-state volume of distribution of 1.6 (1.2-2.8) L/kg; total clearance of 10.2 (8.6-15.1) mL/h/kg; renal clearance of 10.0 (7.9-13.8) mL/h/kg; and terminal disposition half-life of 168 (111-278) h. Following single-dose im administration, significantly more subjects complained of pain following administration of teicoplanin (58%) compared with placebo (4%). Teicoplanin was completely absorbed with a median (range) peak serum concentration of 12.3 (6.6-37.5) micrograms/mL occurring at a median (range) time of 4.1 (0.7-6.1) h. Since the 90% confidence interval for the ratio of areas under the serum concentration-time curve falls within the range of 80 to 120%, the extent of systemic absorption of teicoplanin following im administration is equivalent to that following iv administration.

Teicoplanin pharmacokinetics in intravenous drug abusers being treated for bacterial endocarditis.

The pharmacokinetics of teicoplanin were determined after multiple 30-min intravenous infusions of 10 to 15 mg/kg every 12 to 24 h in 11 intravenous drug abuse (IVDA) patients being treated for bacterial endocarditis. Multiple serum samples were obtained over 7 to 14 days. Twenty-four-hour urine collections were obtained on days 1 and 5. Serum concentration-time data were analyzed by using multiple-dose pharmacokinetic analysis (NONLIN84). Results were compared with pharmacokinetic parameters derived from previous studies in normal healthy volunteers following multiple intravenous infusions of teicoplanin (3 to 6 mg/kg/day). Total and renal clearances of teicoplanin in IVDA patients were found to be significantly greater and more highly variable than those observed previously in normal healthy volunteers. As a result, predicted steady-state trough concentrations in serum may vary up to fivefold. The mechanism responsible for this variation appears to be related to the glomerular filtration rate. In IVDA patients, individualized teicoplanin dosage may be required in the treatment of bacterial endocarditis.

Comparative in vitro activity of teicoplanin and vancomycin against United States teicoplanin clinical trial isolates of gram-positive cocci.

In this study, the in vitro activity of teicoplanin and vancomycin was directly compared against 503 Gram-positive cocci isolated during the U.S. teicoplanin clinical trials. Both antibiotics were equally active against oxacillin-sensitive Staphylococcus aureus, oxacillin-sensitive and oxacillin-resistant Staphylococcus epidermidis, and other coagulase-negative staphylococci, except Staphylococcus haemolyticus. Teicoplanin was fourfold more active than vancomycin against oxacillin-resistant S. aureus (MIC90, 0.5 vs. 2.0 micrograms/ml), whereas vancomycin was more active than teicoplanin (MIC90, 2.0 vs. 8.0 micrograms/ml) against oxacillin-resistant S. haemolyticus. Teicoplanin was two- to eightfold more active than vancomycin against the streptococci and enterococci tested.

Flavonoid modulation of murine neutrophil cytokinesis.

Flavonoids are known to produce a wide range of immunomodulatory effects. In this study, flavone and six hydroxylated analogues were examined for their effect on the FMLP-directed and the random migration of murine peritoneal exudate neutrophils. Flavone significantly (p less than 0.01) inhibits both directed and random migration at an assay concentration of 100 microM. In contrast, fisetin, kaempferol, chrysin, flavonol, morin and quercetin (in decreasing order of activity) significantly (p less than 0.05 to less than 0.01) enhance both directed and random migration at concentrations of 1.0 to 100 microM. Hydrophobicity does not appear to play a key role in the observed compound activity but the number and position of the hydroxyl substitutions might be important. In addition, the [Ca++] modulator chlorpromazine was found to significantly (10 microM; p less than 0.01) inhibit fisetin-enhanced FMLP-directed migration.

Teicoplanin pharmacokinetics in patients undergoing continuous ambulatory peritoneal dialysis after intravenous and intraperitoneal dosing.

The pharmacokinetics of teicoplanin after single 6-mg/kg intravenous and intraperitoneal doses were studied in five noninfected patients undergoing continuous ambulatory peritoneal dialysis. Biological samples were assayed for teicoplanin content by a microbiological assay technique. Terminal disposition half-life (266.4 +/- 51.9 h [mean +/- standard error of the mean]) was prolonged and total body clearance (0.040 +/- 0.004 ml/min per kg) was reduced compared with values previously reported in subjects with normal renal function. The volume of distribution at steady state (1.15 +/- 0.19 liters/kg) was higher than values previously reported in subjects with normal renal function (0.56 to 0.72 liter/kg). Peritoneal dialysis clearance (0.007 +/- 0.001 ml/min per kg) accounted for only 16.1% of total body clearance. The absolute systemic bioavailability of teicoplanin after intraperitoneal administration was 81.5 +/- 10.7%.