bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-dose pharmacokinetics and tolerance of a cholesteryl sulfate complex of amphotericin B administered to healthy volunteers
Authors: Sanders S W , Buchi K N , Goddard M S , Lang J K , Tolman K G
Published: June 2012

Twenty-three healthy volunteer subjects received a single dose of amphotericin B colloidal dispersion or placebo (4:2) in a double-blind, randomized, dose-escalating design. Doses ranged from 0.25 to 1.5 mg/kg of body weight. The medication was administered via intravenous infusion at a rate of 0.5 mg/kg/h. Plasma amphotericin B concentrations increased with increasing doses, resulting in a linear increase in the amphotericin B area under the curve. Concentrations in plasma decreased rapidly upon discontinuation of the infusion, indicating rapid tissue distribution. A log-linear biexponential elimination phase was observed. A three-compartment open model was used to describe the distribution and elimination of amphotericin B. The mean terminal elimination half-life ranged from 86 h at the 0.25-mg/kg dose level to 244 and 235 h at the 1.0- and 1.5-mg/kg dose levels, respectively. Mean total body clearance ranged from 219 to 284 ml/kg/h. The volume of distribution increased with dose, from 3.37 liter/kg at the 0.25-mg/kg dose to 7.92 liter/kg at the 1.5-mg/kg dose. At the lowest dose level, 0.25 mg/kg, the medication was generally well tolerated. Progressive increases in the dose led to increasing side effects. At the 1.5-mg/kg dose level, 50% of the patients on active medication experienced nausea, vomiting, and chills. Physical examinations, ophthalmologic examinations, and clinical laboratory parameters remained within normal limits compared with those obtained during prestudy examinations.
Pharmacokinetics of carumonam (AMA-1080) in patients with impaired renal function and in those undergoing hemodialysis
Authors: Konishi K , Suzuki H , Saruta T , Deguchi N , Fugono T
Published: June 2012

The pharmacokinetics of carumonam (AMA-1080) were studied after a single intravenous 1.0-g dose was given to 26 subjects grouped according to their renal functions. Creatinine clearance (CLCR) was above 85, 50 to 84, 10 to 49, and below 10 ml/min/1.73 m2 in groups 1, 2, 3, and 4, respectively. All of the six patients in groups 4 were receiving maintenance hemodialysis, and they were studied both during and between hemodialysis sessions. Carumonam obeyed two-compartment model kinetics in all four group. The volume of distribution based on the area under serum concentration-time curve (Varea) did not differ significantly among the four groups, the mean value being 0.309 +/- 0.084 liter/kg. The elimination-phase (beta) half-lives were 1.53 +/- 0.36, 2.00 +/- 0.64, 5.08 +/- 1.85, and 12.8 +/- 4.1 h in groups 1, 2, 3, and 4, respectively. The 0- to 24-h cumulative urinary recoveries of carumonam were 83 +/- 11, 76 +/- 20, 58 +/- 25, and 12 +/- 9% of the administered dose in groups 1, 2, 3, and 4, respectively. The systemic and the renal clearances of carumonam decreased according to the severity of renal dysfunction, and the nonrenal clearance, which was calculated as the difference between renal and systemic clearances also decreased as CLCR decreased. A significant positive correlation existed between beta and CLCR (r = 0.847, P less than 0.01), and the beta of carumonam could be predicted by the following equation: beta (h-1) = 0.00460 X CLCR (ml/min/1.73 m2) + 0.049. Hemodialysis shortened the elimination-phase half-lives from 12.8 +/- 4.1 to 2.66 +/- 1.49 h in the six subjects in group 4. A 5-h hemodialysis in a hypothetical anephric subject weighing 60 kg was estimated to remove 51.4% of the drug present in the body at the start of hemodialysis.
Effects of amoxicillin-clavulanate combination on the motility of the small intestine in human beings
Authors: Caron F , Ducrotte P , Lerebours E , Colin R , Humbert G , Denis P
Published: June 2012

The amoxicillin-clavulanate combination (Augmentin) frequently induces gastric complaints and diarrhea by an unknown mechanism. The aim of this study was to assess the effects of two orally therapeutic regimens of amoxicillin-clavulanate on small bowel motility in human beings. Duodeno-jejunal manometric recordings were performed in six healthy subjects treated in a cross-over double-blind study with placebo; amoxicillin-clavulanate, 1 g plus 250 mg per os every 12 h for 3 days; or amoxicillin-clavulanate, 1 g plus 250 mg per os every 12 h on day 3 only (1-day regimen). Recordings were all performed on day 3 during a diurnal fasting period, a fed state after a standard dinner, and a nocturnal fasting period. Amoxicillin-clavulanate did not affect the motility of the small intestine during the diurnal fast or the fed state. During the nocturnal fast, amoxicillin-clavulanate significantly increased the motility index of the nonpropagated contractions and tended to increase the duration and the amplitude of the propagated contractions. The same digestive motor effect was already observed on the first day of treatment (1-day regimen). This study demonstrates that the oral administration of a therapeutic regimen of amoxicillin-clavulanate is associated, in most cases, with the occurrence of small intestinal motor disturbances.
Structure-activity relationships of pentamidine analogs against Giardia lamblia and correlation of antigiardial activity with DNA-binding affinity
Authors: Bell C A , Cory M , Fairley T A , Hall J E , Tidwell R R
Published: June 2012

1,5-Di(4-amidinophenoxy)pentane (pentamidine) and 38 analogs of pentamidine were screened for in vitro activity against the enteric protozoan Giardia lamblia WB (ATCC 30957). All compounds were active against G. lamblia as measured by a [methyl-3H]thymidine incorporation assay. Antigiardial activity varied widely, with 50% inhibitory concentrations (IC50s) ranging from 0.51 +/- 0.13 microM (mean +/- standard deviation) for the most active compound to over 100.0 microM for the least active compounds. The IC50 of the most potent antigiardial agent, 1,3-di(4-amidino-2-methoxyphenoxy)propane compared favorably with the IC50s of the compounds currently used to treat giardiasis, i.e., furazolidone (1.0 +/- 0.03 microM), metronidazole (2.1 +/- 0.80 microM), quinacrine HCl (0.03 +/- 0.02 microM), and tinidazole (0.78 +/- 0.48 microM). A mode of antigiardial activity for these compounds was suggested by the correlation observed between antigiardial activity and the binding of the compounds to calf thymus DNA and poly(dA).poly(dT).
Significance of inducible cephalosporinase remaining in the experimentally infected rat granuloma pouch after beta-lactam therapy
Authors: Araki H , Minami S , Watanabe Y , Yasuda T
Published: June 2012

We studied the influence of inducible cephalosporinase on levels of secondarily administered beta-lactam antibiotics in exudates using experimentally infected rat granuloma pouches. Cefoperazone or cefmetazole was administered intramuscularly at a dose of 100 mg/kg of body weight to rats at 2 and 8 h after infection of rat pouches with Serratia marcescens W-24, which possesses an inducible type I beta-lactamase (cephalosporinase). Subsequently, cefotaxime or cefbuperazone was administered at an intravenous dose of 100 mg/kg to rats at 24 h postinfection. Levels of cefotaxime in the pouch exudates of the cefmetazole-pretreated group were lower than those in the control group, which was infected but not pretreated with antibiotics. This was due to the inactivation of cefotaxime by extracellular cephalosporinase which was induced by cefmetazole and which remained in the rat pouches. However, cefotaxime concentrations were not reduced in the cefoperazone-pretreated group because of the low inducibility of cefoperazone against cephalosporinase production. On the other hand, cefbuperazone concentrations were similar in all groups (control, cefoperazone pretreated, and cefmetazole pretreated), because cefbuperazone is more stable against this enzyme than cefotaxime is. In conclusion, concentrations of secondarily administered beta-lactam antibiotics are affected by inducibly produced cephalosporinase at the infection site when a good inducer like cefmetazole is administered beforehand.
Hippocampal activity in the presence of quinolones and fenbufen in vitro
Authors: Dimpfel W , Spüler M , Dalhoff A , Hofmann W , Schlüter G
Published: June 2012

Rare side effects on the central nervous system including dizziness, restlessness, and even very rare convulsions as reported during the course of antibiotic treatment with quinolones were the topic of a well-controlled in vitro approach. The excitability of brain matter was tested by electrically evoking field potentials in the CA1 region of the rat hippocampus in vitro. Direct effects of nalidixic acid, enoxacin, pefloxacin, norfloxacin, ofloxacin, and ciprofloxacin were found to occur as a dose-dependent increase in amplitude of this field potential, which is in line with the view that the quinolones increase excitability. The highest increase was found with enoxacin and nalidixic acid, and the lowest increase was found with ciprofloxacin. In order to keep the potential risk of the antibiotic therapy as low as possible, ciprofloxacin might be the drug of choice of the quinolones. In contrast to the quinolones, which only increased the amplitudes of electrically evoked potentials, fenbufen induced spontaneous firing in the pyramidal cell layer without stimulation in addition to its dose-dependent effects on the amplitudes of the evoked potentials. Threshold doses of the quinolones tested (0.25 microM) increased the amplitudes of evoked potentials in the presence of an otherwise ineffective concentration of fenbufen (1 microM) to different degrees, ranging from 39.2% for ciprofloxacin to 72.6% for enoxacin.
Comparative pharmacokinetics of amphotericin B after administration of a novel colloidal delivery system, ABCD, and a conventional formulation to rats
Authors: Fielding R M , Smith P C , Wang L H , Porter J , Guo L S
Published: June 2012

The pharmacokinetics and tissue distribution of two amphotericin B dosage forms were compared in rats. A novel lipid-based colloidal delivery system for amphotericin B (Amphotericin B Colloidal Dispersion [ABCD]) which reduces the toxicity of amphotericin B in animals was compared with a conventional micellar formulation. Male Sprague-Dawley rats received a single intravenous injection of 1.0 mg of ABCD, 5.0 mg of ABCD, or 1.0 mg of micellar amphotericin B per kg. Plasma and tissue samples were obtained at 0.5 to 96 h after dosing and analyzed for amphotericin B by high-pressure liquid chromatography. Animals receiving ABCD demonstrated reduced peak levels in plasma, a three- to sevenfold reduction in amphotericin B delivery to the kidneys (the major target organ for toxicity), and prolonged residence time compared with those receiving the micellar formulation. In contrast, amphotericin B concentrations in the liver were two- to threefold higher with ABCD than with the micellar formulation: nearly 100% of the amphotericin B administered as ABCD was recovered from the liver 30 min after dosing. These results suggest that the colloidal particles of ABCD are taken up by the liver, which then acts as a reservoir of amphotericin B.
Comparative inhibition of hepatitis B virus DNA polymerase and cellular DNA polymerases by triphosphates of sugar-modified 5-methyldeoxycytidines and of other nucleoside analogs
Authors: Matthes E , Reimer K , von Janta-Lipinski M , Meisel H , Lehmann C
Published: June 2012

Of a series of 14 nucleoside 5'-triphosphates, those of 2',3'-dideoxy-3'-fluoro-5-methylcytidine, 3'-azido-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoroguanosine, 2',3'-didehydro-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoro-5-ethylcytidine, and 2',3'-dideoxy-3'-fluoroadenosine emerged as the most potent inhibitors of hepatitis B virus DNA polymerase (50% inhibitory dose, 0.03 to 0.35 microM). In contrast, cellular DNA polymerases proved to be resistant to (alpha) or partially affected by (beta) these analogs. These compounds are among the most effective and selective inhibitors of endogenous hepatitis B virus DNA polymerase recognized to date.
Use of slime dispersants to promote antibiotic penetration through the extracellular polysaccharide of mucoid Pseudomonas aeruginosa
Authors: Gordon C A , Hodges N A , Marriott C
Published: June 2012

Agents with the potential to reduce Pseudomonas aeruginosa alginate viscosity (slime dispersants) were shown to promote the diffusion of antipseudomonal antibiotics through alginate but were more effective in facilitating the diffusion of gentamicin than that of ceftazidime. EDTA increased the diffusion rates of these antibiotics by factors of 4.0 and 1.5, respectively, although sodium chloride significantly reduced viscosity and enhanced gentamicin diffusion.
Human serum enhances the postantibiotic effect of fluoroquinolones against Staphylococcus aureus
Authors: Davidson R J , Zhanel G G , Phillips R , Hoban D J
Published: June 2012

The postantibiotic effect (PAE) of fluoroquinolones against Staphylococcus aureus was determined in Mueller-Hinton broth and normal human serum. At both 4X and 10X the MIC, serum significantly increased the duration of the PAE in all strains tested (P less than 0.05). Reducing the pH of the serum from 7.9 to 7.2 had no effect on the PAE. Heat treating the serum (56 degrees C, 30 min) reduced the PAE of ciprofloxacin at 10X the MIC approximately 25% (P less than 0.05). The PAE of cloxacillin was reduced approximately 80% in serum, and PAE experiments with gentamicin and cephalexin produced findings similar to those obtained with the fluoroquinolones. Serum increased the MICs of ciprofloxacin and norfloxacin less than twofold and increased the MIC of pefloxacin approximately fourfold. We conclude that normal human serum considerably increases the PAE of fluoroquinolones against S. aureus.
Antifungal effects of the nonlinear pharmacokinetics of cilofungin, a 1,3-beta-glucan synthetase inhibitor, during continuous and intermittent intravenous infusions in treatment of experimental disseminated candidiasis
Authors: Walsh T J , Lee J W , Kelly P , Bacher J , Lecciones J , Thomas V , Lyman C , Coleman D , Gordee R , Pizzo P A
Published: June 2012

Cilofungin (LY-121019) is a fungicidal cell wall-active 1,3-beta-glucan synthetase inhibitor with a short plasma half-life and saturable nonlinear plasma pharmacokinetics. To optimize the in vivo efficacy of this compound, we studied the effects of its linear and nonlinear pharmacokinetics during continuous versus intermittent intravenous infusion of cilofungin in the treatment of experimental disseminated candidiasis in persistently granulocytopenic rabbits. Six groups of rabbits were studied, untreated controls (n = 32) and five cilofungin dosage regimen groups consisting of the following: 25 mg/kg of body weight intravenously twice daily (VLoINT) (n = 9); 50 mg/kg twice daily (LoINT) (n = 9); 90 mg/kg twice daily (HiINT) (n = 11); 5 mg/kg/h for 18 h/day (LoCI) (n = 7); and 10 mg/kg/h for 18 h/day (HiCI) (n = 7). All regimens achieved plasma concentrations exceeding the MIC for Candida albicans (0.25 microgram/ml). In vitro timed kill assays found that the fungicidal activity and rate of kill by cilofungin above the MIC for C. albicans was concentration dependent. At the lower dosage regimens (VLoINT, LoINT, and LoCI), cilofungin followed linear plasma pharmacokinetics, whereas at higher doses (HiCI and HiINT), nonlinear kinetics consistent with a saturated elimination pathway(s) were observed. Only HiCI and HiINT produced a 10(3)- to 10(4)-fold reduction in CFU per gram in candidiasis of the brain (P less than or equal to 0.001). HiCI and HiINT also significantly reduced infection in the choroid (P less than or equal to 0.05). All regimens, except VLoInt, significantly (P less than or equal to 0.01) reduced tissue infections in lung, liver, spleen, and kidney. However, only the regimens with nonlinear saturation kinetics (HiCI and HiINT) produced a 10(6) reduction in the spleen and a > 10(5) reduction of C. albicans in the kidney and liver. A simple doubling of the dosage from LoCI to HiCI resulted in tissue concentrations that were 10 times higher and a 10(2)- to 10(4)-fold-greater antifungal effect. There was a direct correlation (r2 = 0.83) between tissue concentrations of cilofungin and antifungal activity. Thus, continuous and intermittent infusion dosage regimens that elicit nonlinear saturation plasma pharmacokinetics of cilofungin were associated with increased antifungal activity against experimental disseminated candidiasis.
Pneumocystis carinii dihydrofolate reductase used to screen potential antipneumocystis drugs
Authors: Broughton M C , Queener S F
Published: June 2012

Pneumocystis carinii was obtained in high yield from the lungs of immunosuppressed rats by rupturing mammalian host cells, washing away the soluble mammalian dihydrofolate reductase, and harvesting intact organisms in association with the mammalian plasma membranes. P. carinii dihydrofolate reductase, measured in the 100,000 x g supernatant from sonicated organisms, was obtained in yields ranging up to 62 IU per rat. The enzyme prepared in the presence of protease inhibitors was stable when frozen in liquid nitrogen. P. carinii dihydrofolate reductase differed from the mammalian enzyme in that the former was slightly inhibited by 150 mM KCl, whereas the latter was stimulated over twofold by 150 mM KCl. The standard assay for P. carinii dihydrofolate reductase contained 0.12 mM NADPH and 92 microM dihydrofolic acid. Under these conditions, the 50% inhibitory concentrations of the known inhibitors trimethoprim, trimetrexate, and pyrimethamine were 12 microM, 42 nM, and 3.8 microM, respectively. These standard compounds were also tested against dihydrofolate reductase from rat liver to allow an assessment of the selectivity of the drugs. Although it was the least potent, trimethoprim was the most selective. Pyrimethamine was more potent but was nonselective. Trimetrexate was extremely potent but was selective for mammalian dihydrofolate reductase. A series of experimental compounds was obtained from the National Cancer Institute and other sources through the Developmental Therapeutics Branch of the Division of AIDS at the National Institute of Allergy and Infectious Diseases. Among the first 87 compounds tested, 11 had 50% inhibitory concentrations below that of trimetrexate and 3 were more selective than trimethoprim. The most promising compounds in this original group were chemically related to methotrexate.
Cardiovascular and autonomic pharmacology of the macrolide antibiotic LY281389 in anesthetized beagles and in isolated smooth and cardiac muscles
Authors: Colbert W E , Turk J A , Williams P D , Buening M K
Published: June 2012

As part of the preclinical safety evaluation process, an investigational macrolide antibiotic, LY281389, was examined for autonomic activity in isolated smooth and cardiac muscle preparations and for cardiovascular effects by intravenous infusion in anesthetized beagles. Concentration-dependent antagonism of acetylcholine and angiotensin I (guinea pig ileum), norepinephrine (rat vas deferens), and isoproterenol (guinea pig atria) was observed at LY281389 concentrations of greater than or equal to 10(-5) M. At LY281389 concentrations of greater than or equal to 10(-4) M, the response of the guinea pig ileum to electrical stimulation was also inhibited approximately 65 to 100%, indicative of potential anticholinergic or alpha-adrenergic activity. In anesthetized dogs, the predominant effect of LY281389 was an increase in heart rate at doses of greater than or equal to 200 micrograms/kg of body weight. LY281389 also produced slight increases in mean arterial pressure and shortening of the P-R interval of the electrocardiogram. In summary, LY281389 possesses nonselective receptor antagonist activity in vitro and produces cardiovascular stimulation in anesthetized dogs. These results indicate that, in addition to potent antimicrobial activity, the macrolide antibiotic LY281389 may exert unexpected actions on cardiovascular function.
Molecular distribution of ROB-1 beta-lactamase in Actinobacillus pleuropneumoniae
Authors: Juteau J M , Sirois M , Medeiros A A , Levesque R C
Published: June 2012

The plasmid content and molecular distribution of the ROB-1 beta-lactamase was investigated in 31 swine isolates of Actinobacillus pleuropneumoniae. Three types of plasmid patterns were observed in ampicillin-resistant isolates: a predominant one consisting of 2.6-, 2.9-, and 5.0-kb plasmids and two other patterns consisting of 4.2- and 5.5-kb plasmids and of a 6.8-kb plasmid. Plasmid DNA preparations were hybridized with a blaROB-1 intragenic fragment from the Haemophilus influenzae Rrob plasmid. Positive hybridizations were observed with all ampicillin-resistant isolates. The blaROB-1 gene was found on 3 plasmids of 2.6, 5.5, and 6.8 kb. One swine isolate of Pasteurella multocida also had a 2.6-kb plasmid bearing blaROB-1. ROB-1 was confirmed in typical isolates by isoelectric focusing and blaROB-1 sequences were confirmed by polymerase chain reaction amplification with an intragenic set of primers. Plasmids bearing blaROB-1 were successfully electro-transformed in a susceptible A. pleuropneumoniae isolate. These results emphasize the importance of ROB-1 in A. pleuropneumoniae and identify a possible reservoir of beta-lactam resistance.
Correlation between in vitro and in vivo activity of antimicrobial agents against gram-negative bacilli in a murine infection model
Authors: Fantin B , Leggett J , Ebert S , Craig W A
Published: June 2012

We studied the relationship between in vitro susceptibility tests (MICs, MBCs) and in vivo activity of tobramycin, pefloxacin, ceftazidime, and imipenem against 15 gram-negative bacilli from five different species in a murine thigh infection model. Complete dose-response curves were determined for each antimicrobial agent against each strain, and three parameters of in vivo activity were defined: maximal attainable antimicrobial effect (i.e., reduction in log10 CFU per thigh compared with untreated controls) at 24 h (Emax), total dose required to reach 50% of maximal effect (P50), and total dose required to achieve a bacteriostatic effect (static dose). Pefloxacin demonstrated the greatest Emax (P less than 0.05). Tobramycin was the most potent antimicrobial agent, as indicated by its having the lowest static dose/MIC ratio (P less than 0.002). Log10 P50s and static doses correlated significantly with log10 MICs or MBCs for the 15 strains of each antibiotic (P less than 0.01) except imipenem (P greater than 0.50). The greater potency of imipenem against the three Pseudomonas aeruginosa strains than against strains of the family Enterobacteriaceae (P less than 0.01) explained this lack of correlation. A longer duration of postantibiotic effect for imipenem against P. aeruginosa (P = 0.02) contributed to its increased potency against these strains. We conclude that in vitro susceptibility tests correlated well with in vivo activity in this animal model and that variations in potency among the four antimicrobial agents could be explained by differences in pharmacokinetics or pharmacodynamic activity.
Evaluation of SQ 34,514: pharmacokinetics and efficacy in experimental herpesvirus infections in mice
Authors: Braitman A , Swerdel M R , Olsen S J , Tuomari A V , Lynch J S , Blue B , Michalik T , Field A K , Bonner D P , Clark J M
Published: June 2012

The new antiviral nucleoside SQ 34,514 [(1R-1 alpha, 2 beta, 3 alpha)-2-amino-9- [2,3-bis(hydroxymethyl)cyclobutyl]-6H-purin-6-one], the active R isomer of racemic SQ 33,054 (cyclobut-G), was evaluated for efficacy in the treatment of herpesvirus infections in mice. SQ 34,514 was orally efficacious in a herpes simplex virus type 1 (HSV-1) systemic infection, an intracerebral HSV-2 infection, a vaginally induced HSV-2 infection in ovariectomized mice, and in a systemic murine cytomegalovirus infection. SQ 34,514 compared favorably with acyclovir and ganciclovir in the treatment of these experimental infections. In mice, SQ 34,514 had an oral bioavailability of 80% based on urinary excretion. SQ 34,514 may have potential value in the therapy of HSV and cytomegalovirus infections in humans.
Quinine uptake by human polymorphonuclear neutrophils
Authors: el Benna J , Pasquier C , Labro M T
Published: June 2012

The antimalarial drug quinine has been shown to impair human polymorphonuclear leukocyte (PMN) functions. To gain insight into the mechanism of this phenomenon, we investigated quinine uptake by PMN with a fluorometric assay based on the fluorescence properties of this drug. After 30 min of incubation at 37 degrees C in the presence of 1 and 10 micrograms of quinine per ml, PMN-associated quinine reached 90 +/- 6 and 780 +/- 150 ng/2.5 x 10(6) PMN, respectively, giving a cellular-to-extracellular concentration ratio of 140 to 150. A steady state was reached within 5 min. Uptake was partially dependent on temperature, cell viability, and extracellular pH. Fractionation studies showed that 30 to 40% of the PMN-associated quinine was located in the particulate fraction. The efflux of PMN-associated quinine was rapid and complete when the incubation mixture was replaced by drug-free medium. These data suggest that several mechanisms are involved in the uptake of quinine by PMN, including a viability- and energy-independent process possibly related to reversible association of quinine to cell structures (particularly the membrane). Other mechanisms could involve trapping by protonation and/or active PMN transport systems. Thus, most of the quinine taken up by resting PMN is found in the soluble fraction of disrupted cells. This may partly explain the depressive properties of quinine.
Structural requirements of tetracycline-Tet repressor interaction: determination of equilibrium binding constants for tetracycline analogs with the Tet repressor
Authors: Degenkolb J , Takahashi M , Ellestad G A , Hillen W
Published: June 2012

We used the Tn10-encoded Tet repressor, which has a highly specific binding capacity for tetracycline, to probe contacts between the drug and protein by chemical interference studies of the antibiotic. For that purpose, the equilibrium association constants of modified tetracyclines with the Tet repressor and Mg2+ cations were determined quantitatively. The results confirm the previous notion that Mg2+ probably binds with the oxygens at positions 11 and 12 and is absolutely required for protein-drug recognition. Modifications were introduced at positions seven, six, five, and four of the drug, and anhydrotetracycline was also studied. Substitutions or eliminations of functions at these positions influenced binding to the Tet repressor up to 35-fold. The introduction of an azido function at position seven in 7-azidotetracycline and epimerization of the substituents at position four in 4-epitetracycline lead to a 2- or 25-fold reduction, respectively, of Tet repressor affinity in those compounds. Anhydrotetracycline bound about 35-fold more strongly than tetracycline did, indicating that the oxygen at position 11 may be involved in Tet repressor recognition. This increased binding is in contrast to the lower antibiotic activity of anhydrotetracycline and indicates that the Tet repressor and ribosomes recognize the drug differently.
Prolonged and potent therapeutic and prophylactic effects of (S)-1-[(3-hydroxy-2-phosphonylmethoxy)propyl]cytosine against herpes simplex virus type 2 infections in mice
Authors: Yang H , Datema R
Published: June 2012

The acyclic nucleotide analog (S)-1-[(3-hydroxy-2-phosphonylmethoxy)propyl]cytosine (HPMPC) is a potent and selective inhibitor of herpesviruses. Cells preincubated with HPMPC are refractory to herpes simplex virus type 2 (HSV-2) infection for several days after removal of the drug from the medium. A single administration of 30 mg of HPMPC per kg of body weight 4 days prior to virus infection intraperitoneally with HSV-2 (strain G) completely protected mice from death, and the protective effect was dose dependent. HPMPC was equally efficacious in protecting mice when the same total amount of the drug was administered as a single dose as when it was given daily in several smaller doses (5 mg/kg with treatment initiation at 3 h postinfection [p.i.], 90 versus 80% survival, respectively). In contrast, ganciclovir [9(1,3-dihydroxy-2-propoxymethyl)guanine] was more efficacious when it was given daily than it was when it was given less than daily in a late stage of HSV-2 infection (100 mg/kg; when mice were treated 96 h p.i., 80 versus 50% survival, respectively; when mice were treated 120 h p.i., 60 versus 20% survival, respectively). Therefore, single doses of HPMPC were more effective than ganciclovir in protecting mice from death (80 versus 20% survival, respectively; P less than 0.05), whereas there was no difference when the drugs were given daily (50 versus 60% survival, respectively). Our studies suggest a potential of HPMPC for conventional and prophylactic treatments of herpesvirus infections with infrequent drug administration.
Nosocomial spread of an amikacin resistance gene on both a mobilized, nonconjugative plasmid and a conjugative plasmid
Authors: Hopkins J D , Flores A , del Pilar Pla M , Lester S , O'Brien T F
Published: June 2012

Resistance to amikacin among members of the family Enterobacteriaceae at a hospital in Venezuela rose from 2% in 1979 to 5% in 1984 and 10% in 1985 as amikacin usage rose 20-fold to exceed gentamicin usage. Resistance to gentamicin remained at 25 to 27%. We examined the plasmids from 21 isolates obtained in 1984 and 1985. Nine of eleven in 1984 and three of ten in 1985 carried aacA and sul on a 3.8-kb BamHI fragment of pBWH300, a 10.4-kb nonconjugative plasmid that had been mobilized into strains of six species by at least two different coresident conjugative plasmids. Six 1985 isolates of two species carried these genes on a similar BamHI fragment of the 104-kb conjugative plasmid pBWH303. One isolate in 1984 and one in 1985 carried the 69-kb conjugative plasmid pBWH301, which had aacA as the promoter-proximal gene of an operon that also encompassed the cat and aadB resistance genes. Another conjugative plasmid, pBWH302, was found in a single isolate. It carried a different aacA allele on the functional transposon Tn654, which appeared to be closely related to Tn1331, a transposon previously isolated in Argentina and Chile. Increased selection may thus have led to dissemination of an endemic aacA allele on two endemic plasmids, one spread by mobilization, with occasional intrusion of additional aacA alleles from outside.
Beta-lactamase of Mycobacterium fortuitum: kinetics of production and relationship with resistance to beta-lactam antibiotics
Authors: Fattorini L , Scardaci G , Jin S H , Amicosante G , Franceschini N , Oratore A , Orefici G
Published: June 2012

The kinetics of both intracellular and extracellular beta-lactamase production and the relationship between extracellular enzyme and in vitro susceptibility of Mycobacterium fortuitum to beta-lactam antibiotics have been studied. To this end we used a panel of stable nitrosoguanidine-induced mutants of M. fortuitum derived from the parental strain ATCC 19542 and differing in beta-lactamase production from 0.0001 to 278 U/liter in Mueller-Hinton broth. For overproducers of beta-lactamase (mutants A188, B180, C207, D316, and E31), MICs of benzylpenicillin, amoxicillin, ampicillin, and cephaloridine progressively increased with the amount of enzyme released into the medium, whereas MICs of imipenem and cefoxitin did not. The resistance of the mutants to amoxicillin was reduced up to 32-fold by clavulanic acid, whereas that to ampicillin was reduced 8-fold by sulbactam. These data suggest that the enzyme participated in the mechanisms of resistance to the beta-lactam antibiotics. However, for a mutant of M. fortuitum (gamma 27) with virtually nonexistent beta-lactamase production, the antibiotics still had relatively high MICs (for instance, benzylpenicillin and cephaloridine had MICs of 64 and 32 micrograms/ml, respectively). This suggests that, aside from beta-lactamase production, other mechanisms such as cell wall permeability and/or affinity for penicillin-binding proteins could coexist in M. fortuitum and explain its natural resistance to beta-lactam antibiotics.
Pharmacokinetics of ampicillin and sulbactam in patients undergoing heart surgery
Authors: Wildfeuer A , Müller V , Springsklee M , Sonntag H G
Published: June 2012

The pharmacokinetics of ampicillin and sulbactam, a new beta-lactamase inhibitor, were investigated in 16 patients undergoing prosthetic cardiac valve insertion. The combination of 2 g of ampicillin and 1 g of sulbactam was administered as perioperative prophylaxis intravenously over 3 to 6 days. Several serum pharmacokinetic parameters were similar for the two drugs after three intravenous doses were given to patients following surgery. The half-lives of elimination of ampicillin and sulbactam were 79 +/- 4.9 and 88 +/- 5.9 min, the volumes of distribution were 15.6 +/- 1.4 and 17.7 +/- 1.2 liters/70 kg, and the total plasma clearances were 144.4 +/- 14.5 and 147.2 +/- 14.5 ml/min, respectively. The peak concentrations of ampicillin and sulbactam in serum were calculated to be 134.3 +/- 1.3 and 58.3 +/- 1.2 micrograms/ml, respectively. Ampicillin and sulbactam rapidly penetrated from the blood into various tissues collected during heart surgery, such as sternum, pericardium, myocardium, and endocardium. The concentrations of ampicillin in tissue ranged from 17.8 +/- 9.9 to 50 +/- 29.5 micrograms/g, and those of sulbactam in tissue ranged from 8.8 +/- 6.2 to 19.6 +/- 10.1 micrograms/g. The concentrations of ampicillin and sulbactam in serum and tissue also apparently exceeded the MICs against most beta-lactamase-producing bacteria usually involved in postoperative wound infections and prosthetic valve endocarditis. The ratio of the two compounds was approximately 2:1 in serum and in the various tissues affected by the operation. The pharmacokinetics of ampicillin and sulbactam in serum and investigated tissues suggest that the combination of the two beta-lactams will be effective in the perioperative prophylaxis of patients undergoing heart surgery.
Choice of antibiotic in nonelective cesarean section
Authors: Hager W D , Rapp R P , Billeter M , Bradley B B
Published: June 2012

The use of antibiotics for prophylaxis against infection among women undergoing nonelective cesarean section has become the standard of care in the United States. Many different antibiotics have been used successfully. Single-dose regimens administered after the cord is clamped have proven just as effective as multiple-dose regimens. Although the most frequently used class of antibiotics is the cephalosporin family, the single best agent has not been determined. This study was a double-blind, randomized trial in which we compared a narrow-spectrum cephalosporin (cefazolin; n = 63) with an expanded-spectrum cephamycin (cefoxitin; n = 66) and with a broad-spectrum cephalosporin (cefotaxime; n = 60) used as a single-dose prophylaxis in patients undergoing a nonelective cesarean section. Of the 194 patients enrolled in the study, 189 were evaluable. There was no significant difference between the groups in mean age, gravidity, parity, duration of labor, duration of ruptured membranes, number of vaginal examinations, or socioeconomic status (socioeconomic status was defined by third-party coverage). There was no significant difference among the antibiotics in the incidence of immediate or delayed postoperative infections. These data indicate that a less expensive, narrow-spectrum cephalosporin is as effective as more expensive, broader-spectrum cephamycins and cephalosporins as prophylaxis for patients undergoing nonelective cesarean section.
In vitro studies of water activity and bacterial growth inhibition of sucrose-polyethylene glycol 400-hydrogen peroxide and xylose-polyethylene glycol 400-hydrogen peroxide pastes used to treat infected wounds
Authors: Ambrose U , Middleton K , Seal D
Published: June 2012

Water activity and bacterial growth inhibition have been studied in formulations comprising either sucrose or xylose along with polyethylene glycol 400 and hydrogen peroxide. The pastes are chemically stable for 6 months if stored at 2 to 8 degrees C and have been shown to lower water activity to levels below those essential for bacterial growth and to be bactericidal even when diluted up to 50% with serum. Of the organisms tested, Staphylococcus aureus proved the least susceptible to the bactericidal effects of these pastes, and candida and gram-negative organisms proved the most susceptible. Pastes without hydrogen peroxide were less rapidly bactericidal than pastes with hydrogen peroxide, while polyethylene glycol 400 itself was found to have considerable antimicrobial activity. It is suggested that sucrose paste may be of benefit as a treatment for infected and malodorous wounds.
Intranuclear accumulation of subgenomic noninfectious human cytomegalovirus DNA in infected cells in the presence of ganciclovir
Authors: Hamzeh F M , Lietman P S
Published: June 2012

In preparation for an attempt to elucidate some aspects of the interaction between ganciclovir and human cytomegalovirus (HCMV) DNA replication in cells infected with HCMV, we developed a dot blot DNA-DNA hybridization technique to quantify intracellular HCMV DNA replication. We studied the effect of ganciclovir on the time course of HCMV DNA replication in human fibroblasts. Ganciclovir resulted in complete cessation of the production of infectious virus, as detected by the plaque assay. However, viral DNA synthesis, as measured by dot blot DNA-DNA hybridization with cloned HCMV DNA BamHI C fragment probe, continued in the presence of ganciclovir at 10 times the 50% effective dose (i.e., 10 micrograms/ml). The continuation of viral DNA synthesis in ganciclovir-treated cultures leads to the intranuclear accumulation of short (subgenomic) HCMV DNA fragments. These DNA fragments are neither packaged nor released into the culture medium. Furthermore, the short DNA fragments were detected only by the BamHI C probe from the center of the unique long segment of the HCMV genome. The failure of the DNA probes from the termini of HCMV genome (BamHI-Q and HindIII-M) to detect the short DNA fragments and the intranuclear localization of these fragments suggest that these short fragments may lack the signal sequences necessary for packaging and release as infectious virions. These data strongly suggest that the anti-HCMV activity of ganciclovir is due mainly to the prevention of viral DNA chain elongation which results in the intranuclear accumulation of incomplete noninfectious viral DNA fragments.
Bactericidal effects of antibiotics on slowly growing and nongrowing bacteria
Authors: Eng R H , Padberg F T , Smith S M , Tan E N , Cherubin C E
Published: June 2012

Antimicrobial agents are most often tested against bacteria in the log phase of multiplication to produce the maximum bactericidal effect. In an infection, bacteria may multiply less optimally. We examined the effects of several classes of antimicrobial agents to determine their actions on gram-positive and gram-negative bacteria during nongrowing and slowly growing phases. Only ciprofloxacin and ofloxacin exhibited bactericidal activity against nongrowing gram-negative bacteria, and no antibiotics were bactericidal (3-order-of-magnitude killing) against Staphylococcus aureus. For the very slowly growing gram-negative bacteria studied, gentamicin (an aminoglycoside), imipenem (a carbapenem), meropenem (a carbapenem), ciprofloxacin (a fluoroquinolone), and ofloxacin (a fluoroquinolone) exhibited up to 5.7 orders of magnitude more killing than piperacillin or cefotaxime. This is in contrast to optimally growing bacteria, in which a wide variety of antibiotic classes produced 99.9% killing. For the gram-positive and gram-negative bacteria we examined, antibiotic killing was greatly dependent on the growth rate. The clinical implications of slow killing by chemotherapeutic agents for established bacterial infections and infections involving foreign bodies are unknown.
Pharmacokinetics and adverse effects of 20-mg/kg/day trimethoprim and 100-mg/kg/day sulfamethoxazole in healthy adult subjects
Authors: Stevens R C , Laizure S C , Williams C L , Stein D S
Published: June 2012

The pharmacokinetics of trimethoprim-sulfamethoxazole were studied in 12 healthy adult subjects receiving trimethoprim at 20 mg/kg of body weight per day and sulfamethoxazole at 100 mg/kg/day, which is the conventional dose for treating Pneumocystis carinii pneumonia (PCP). Daily doses were evenly divided and orally administered every 6 h for 3 days. Trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole concentrations in serum and urine were measured by high-performance liquid chromatography. Five subjects withdrew from the study because of intolerable gastrointestinal and central nervous system toxicities. In the seven subjects that completed the study, the mean maximum serum drug concentrations after the last dose were 13.6 +/- 2.0, 372 +/- 64, and 50.1 +/- 10.9 micrograms/ml for trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole, respectively. The mean half-lives were 13.6 +/- 3.5, 14.0 +/- 2.3, and 18.6 +/- 4.3 h, respectively. Changes in absolute neutrophil count were significantly correlated with the minimum concentrations of trimethoprim and sulfamethoxazole in serum and trimethoprim area under the concentration-time curve (for all three parameters, r2 = 0.6 and P less than 0.05). Our findings add to the evidence that serum drug concentrations in adults following the conventional dose of trimethoprim-sulfamethoxazole for PCP are excessive and contribute to certain adverse reactions. Further studies are indicated in patients to optimize the dosing regimen of trimethoprim-sulfamethoxazole in the treatment of PCP.
Activity of pentamidine and pentamidine analogs against Toxoplasma gondii in cell cultures
Authors: Lindsay D S , Blagburn B L , Hall J E , Tidwell R R
Published: June 2012

The capabilities of pentamidine and nine pentamidine analogs to inhibit the development of Toxoplasma gondii were examined in vitro. Treatment of infected cultures with pentamidine and five of its analogs caused a significant (P less than 0.05) reduction in the numbers of tachyzoites produced. Analogs of pentamidine may be useful agents in the treatment of toxoplasmosis.
In vitro susceptibilities of Campylobacter jejuni and Campylobacter coli to azithromycin and erythromycin
Authors: Taylor D E , Chang N
Published: June 2012

MICs of azithromycin and erythromycin for 20 Campylobacter coli and 20 Campylobacter jejuni strains were determined. The results demonstrated that, for Campylobacter species, all high-level erythromycin-resistant strains were also resistant to azithromycin and that azithromycin did not exhibit increased potency in comparison with that of erythromycin.
Susceptibility of Staphylococcus species and subspecies to teicoplanin
Authors: Bannerman T L , Wadiak D L , Kloos W E
Published: June 2012

Twenty-four Staphylococcus species and their subspecies were examined for their susceptibilities to teicoplanin by disk diffusion (30-micrograms disk) and agar dilution for the determination of MICs. Moderately susceptible and resistant clinical strains were further tested for their susceptibilities to oxacillin and vancomycin. Teicoplanin resistance was not observed in the reference strains of the various Staphylococcus species isolated from healthy volunteers or animals. However, the novobiocin-resistant species Staphylococcus saprophyticus, Staphylococcus cohnii, Staphylococcus xylosus, Staphylococcus arlettae, Staphylococcus kloosii, and Staphylococcus gallinarum were less susceptible to teicoplanin (MIC, 2 to 8 micrograms/ml) than most of the novobiocin-susceptible species were (MIC, 0.5 to 4 micrograms/ml). Clinical isolates of coagulase-negative species were generally less susceptible to teicoplanin than were reference strains. Seven percent of the Staphylococcus epidermidis clinical strains were moderately susceptible (MIC, 16 micrograms/ml) to teicoplanin. Of these strains, 70% were oxacillin resistant. For Staphylococcus haemolyticus strains, 11% were resistant (MIC, greater than 16 micrograms/ml) and 21% were moderately susceptible to teicoplanin. Of these strains, 95% were oxacillin resistant, No strains of S. epidermidis or S. haemolyticus were intermediate or resistant to vancomycin. Teicoplanin appears to be less active in vitro against oxacillin-resistant S. haemolyticus. However, teicoplanin is an effective antimicrobial agent against many Staphylococcus species.
Potentiation of antibacterial activity of azithromycin and other macrolides by normal human serum
Authors: Pruul H , McDonald P J
Published: June 2012

The interaction of azithromycin with normal human serum was examined in relation to serum protein binding, MIC, and kinetics of killing of bacteria. While the binding of azithromycin to serum proteins is low (8.5% at a concentration of 0.01 mM in 95% serum), the presence of 40% serum during the MIC test decreased MICs by 26-fold for serum-resistant Escherichia coli and 15-fold for Staphylococcus aureus. Erythromycin had a similar but lesser effect, while roxithromycin was less active against S. aureus in the presence of serum. The rate of killing of E. coli and S. aureus by azithromycin was increased in the presence of serum. The enhancement of antibiotic activity by serum was pH independent, and heat inactivation and preabsorption with homologous bacteria failed to inhibit enhancement by serum. The macromolecular incorporation of [3H]thymidine by E. coli continuously exposed to 2 micrograms of azithromycin per ml (0.25x the MIC) and 40% serum was decreased by 80% at pH 7.8 and by 48% at pH 7.2, while azithromycin alone failed to inhibit incorporation. Inhibition of nucleic acid biosynthesis at pH 7.2 in the presence of serum was also detected with sub-MICs of erythromycin, norfloxacin, and gentamicin but not roxithromycin. A diffusible serum factor was shown to interact with azithromycin to inhibit the growth of E. coli in an agar diffusion assay to detect antibiotic-serum synergy.
Structure-activity relationships and mode of action of 5-mercapto-substituted oligo- and polynucleotides as antitemplates inhibiting replication of human immunodeficiency virus type 1
Authors: Bardos T J , Schinazi R F , Ling K H , Heider A R
Published: June 2012

Introduction of a reactive 5-mercapto group into some of the cytosine and/or uracil bases of various oligo- and polynucleotides by partial thiolation resulted in several potent inhibitors of the replication of human immunodeficiency virus type 1 (HIV-1) in primary human lymphocytes. These compounds exhibited little if any toxicity against uninfected peripheral blood mononuclear cells and showed 15 to 75 times higher antitemplate activity against a p66/p51 HIV-1 recombinant reverse transcriptase (RT) than against the DNA polymerase alpha from human lymphocytes. In contrast, the unthiolated oligo- and polynucleotides are void of antitemplate activity, and their apparent inhibitory effect on HIV-1 closely paralleled their toxicity for the cells. Partially thiolated poly(dC) (MPdC) was the most potent of all the compounds tested against HIV-1 in peripheral blood mononuclear cells (50% effective concentration, 1.8 micrograms/ml or 0.019 microM), while showing low cytotoxicity (greater than 100 micrograms/ml). The corresponding unmodified poly(dC) showed no anti-HIV-1 activity at 50 micrograms/ml but had pronounced cytotoxicity. MPdC was also a potent inhibitor of HIV-1 RT (50% inhibitory concentration, 0.30 micrograms/ml). The inhibitory activities of thiolated homooligo(dCs) against both HIV-1 replication and HIV-1 RT increased with increasing chain length. The heterooligonucleotides included in this study were designed as structural analogs of portions of the natural primer of HIV-1 RT, i.e., tRNA(3Lys). An 18-mer analog of the 3' terminus, complementary (antisense) to the primer-binding site of the HIV-1 genome, was attached to an oligo(dC) tail and 5-thiolated; this increased its activity and decreased its toxicity. This compound will serve as a new lead in the development of more effective antitemplates against HIV-1.