bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacokinetics of amikacin in serum and in tissue contiguous with pressure sores in humans with spinal cord injury
Authors: Segal J L , Brunnemann S R , Eltorai I M
Published: June 2012

Pressure sores are a common occurrence in immobilized patients. They increase morbidity and mortality and impede rehabilitation. Antibiotics are routinely used to assist in effecting a cure when infection is present. Nevertheless, for patients with spinal cord injuries (SCI), strategies for effective therapy with antibiotics based on measurement of concentrations in tissue and pharmacokinetic behavior in extravascular spaces do not exist. By analyzing the concentration-time profile and protein binding of amikacin in the interstitial fluid (IF) in contact with pressure sores, we found that the disposition of amikacin in the tissue contiguous with pressure sores appears to be governed by simultaneous first-order and capacity-limited pharmacokinetic behavior. Amikacin disposition in IF proceeded without a simple relationship to amikacin concentrations in serum, and the time course in IF was not accurately simulated by linear models of amikacin pharmacokinetic behavior. Total amikacin clearance estimated from a pharmacokinetic model using simultaneous first-order and nonlinear intercompartmental transfer of amikacin was not significantly different from clearance calculated by us in a prior study of amikacin pharmacokinetic behavior in patients with SCI. In patients with SCI, optimal use of amikacin in the treatment of infected pressure sores is contingent upon accurate characterization of the pharmacokinetic behavior of this aminoglycoside in serum and in the IF in contact with these lesions. Only methods which quantitate amikacin concentration and protein binding in IF and incorporate a model that can simultaneously simulate nonlinear and linear disposition processes should be relied upon to influence therapeutic decision making.
In vitro susceptibilities of oxacillin-resistant Staphylococcus aureus to dapsone and sulfamethoxazole alone and in combination with trimethoprim
Authors: Lambertus M W , Kwok R Y , Mulligan M E
Published: June 2012

The in vitro activity of trimethoprim plus dapsone against oxacillin-resistant Staphylococcus aureus was comparable to that of trimethoprim plus sulfamethoxazole. Because of its different pharmacologic properties, dapsone may be a useful agent in combination with trimethoprim for the treatment of patients colonized with oxacillin-resistant S. aureus.
In vivo assessment of antimicrobial agents against Toxoplasma gondii by quantification of parasites in the blood, lungs, and brain of infected mice
Authors: Piketty C , Derouin F , Rouveix B , Pocidalo J J
Published: June 2012

The in vivo effects of antimicrobial agents against Toxoplasma gondii were evaluated in mice that were infected intraperitoneally with 10(4) tachyzoites of the RH strain by determination of survival rates and study of the kinetics of growth of T. gondii in infected mice. At various intervals after infection, subcultures of serial dilutions of blood, lung, and brain homogenates were performed in fibroblast tissue cultures for determination of parasitic loads. Pyrimethamine (18.5 mg/kg per day), sulfadiazine (375 mg/kg per day), and clindamycin (300 mg/kg per day) were administered for 10 days from day 1 or day 4 after infection. Untreated control mice died within 9 days and showed early and predominant lung involvement. All mice treated with sulfadiazine administered from day 1 survived and were apparently healthy; parasitic loads decreased early after treatment, but a relapse was observed 5 days after the cessation of therapy. When pyrimethamine was administered from day 1, 7 of 11 mice died within 25 days; by determination of parasitic loads, the effect of pyrimethamine was only demonstrable from day 6, and a relapse was constantly observed after the cessation of therapy. When pyrimethamine and sulfadiazine were administered in combination, 100% of mice survived; when therapy was started at day 1, parasites remained undetectable; in mice treated from day 4, parasites were eradicated by day 8 but infection relapsed 8 days after the cessation of therapy. All mice treated with clindamycin from day 1 or day 4 died within 10 days, but parasitemia was always undetectable. These results indicate that study of the kinetics of parasitic loads in blood and organs may provide additional information on the effect of antimicrobial agents against T. gondii in regard to the evolution of the infection and may represent a reliable basis for the determination of therapeutic regimens in humans.
Bactericidal effect of doxycycline associated with lysosomotropic agents on Coxiella burnetii in P388D1 cells
Authors: Raoult D , Drancourt M , Vestris G
Published: June 2012

There is no consistently reliable treatment for endocarditis resulting from chronic Coxiella burnetii infection, the causative agent of Q fever. Although certain antibiotics are recommended on the basis of their in vitro bactericidal activities, results of therapy with these antibiotics are often disappointing. To evaluate whether the currently recommended antibiotic susceptibility tests for C. burnetii give misleading results because of continued division of uninfected cells, thereby resulting in the dilution of infected cells and, hence, a false picture of antibiotic efficacy, we blocked cell division during antibiotic susceptibility testing with cycloheximide. Using this new method, we found that the currently recommended antibiotics for the treatment of Q fever, doxycycline, pefloxacin, and rifampin, did not reduce the ratio of infected to noninfected cells (either L929 or P388D1) by 9 days postinfection. To test the hypothesis that this lack of antibacterial activity is due to antibiotic inactivation by the low pH of the phagolysosomes in which C. burnetii is found, we used alkalinizing lysosomotropic agents (chloroquine or amantadine) concurrently with doxycycline. This resulted in the sterilization of C. burnetii infection in P388D1 cells. This finding seems to confirm our suspicion that the acidic conditions of the phagolysosomes in which C. burnetii is located inhibit antibiotic activity. This inhibition can be reversed in vitro when lysosomotropic alkalinizing agents are used.
Cloning of SHV-2, OHIO-1, and OXA-6 beta-lactamases and cloning and sequencing of SHV-1 beta-lactamase
Authors: Mercier J , Levesque R C
Published: June 2012

Molecular cloning of DNA fragments permitted the isolation of structural genes coding for SHV-1, SHV-2, OHIO-1, and OXA-6 beta-lactamases. DNA probes were constructed for SHV-1, and under conditions of high stringency, hybridization was observed only between SHV-1 and SHV-2. Oligonucleotide typing with a 15-mer SHV-1 probe was capable of discriminating between SHV-1 and SHV-2 but not OHIO-1. The nucleotide sequence of the SHV-1 beta-lactamase gene from plasmid R974 has been determined. The structural gene encodes a polypeptide product which differs by 9 residues from the p453 (SHV-1) PIT-2 enzyme determined by peptide sequencing. The significance of each mutation was assessed by alignment of amino acid sequences and comparisons with the Staphylococcus aureus PC1 penicillinase crystal structure. Structural similarities between SHV-1 and class A beta-lactamases are extensive, with amino acid identities of 88.9% between SHV-1 and LEN-1, 91.8% between SHV-1 and OHIO-1, and 63.7% between SHV-1 and TEM-1.
In vitro susceptibilities of oral pigmented Bacteroides species to trospectomycin and other selected antimicrobial agents
Authors: Johnson C C , Wendeler M , Levison M E
Published: June 2012

The in vitro activity of trospectomycin against 97 clinical isolates of oral pigmented Bacteroides species was compared with the activities of five other antimicrobial agents. At 4 micrograms/ml, more than 90% of isolates were inhibited by trospectomycin. Overall, strains that produced beta-lactamase (n = 41) were more resistant to trospectomycin, penicillin G, cefoxitin, piperacillin, and tetracycline but not to clindamycin. In this study, trospectomycin had excellent in vitro activity against oral pigmented Bacteroides species.
Concentrations of teicoplanin in serum and atrial appendages of patients undergoing cardiac surgery
Authors: Bergeron M G , Saginur R , Desaulniers D , Trottier S , Goldstein W , Foucault P , Lessard C
Published: June 2012

The concentrations of teicoplanin in sera and heart tissues of 49 patients undergoing coronary bypass were measured. Each patient received a 6- or 12-mg/kg dose of teicoplanin administered in a slow intravenous bolus injection over 3 to 5 min beginning at the time of induction of anesthesia. Mean +/- standard error of the mean concentrations in serum were, for the two doses, respectively, 58.1 +/- 1.7 and 123.3 +/- 7.4 micrograms/ml 5 min after administration and 22.2 +/- 0.7 and 56.5 +/- 2.8 micrograms/ml at the time of removal of atrial appendages. Mean +/- standard error of the mean concentrations in tissue were 70.6 +/- 1.7 and 139.8 +/- 2.2 micrograms/g, respectively, giving mean tissue/serum ratios of 3.7 +/- 0.3 and 2.8 +/- 0.2, respectively. Teicoplanin penetrates heart tissue readily and reaches levels in the serum far in excess of the MICs for most pathogens that have been found to cause infections following open heart surgery.
Evidence of a novel staphylococcal mec-encoded element (mecR) controlling expression of penicillin-binding protein 2'
Authors: Tesch W , Ryffel C , Strässle A , Kayser F H , Berger-Bächi B
Published: June 2012

A region was identified on the methicillin resistance determinant (mec) isolated from Staphylococcus epidermidis and cloned into Staphylococcus carnosus which was responsible for a novel downregulation of the expression of methicillin resistance. The presence of this region reduced the overall expression of methicillin resistance and the synthesis of the mec-encoded penicillin-binding protein 2' (PBP 2') in S. carnosus. This region was located by Bal31 deletion mutagenesis upstream of the structural gene for PBP 2'. Deletions within this region resulted in higher levels of expression of methicillin resistance and increased levels of PBP 2' synthesis. We tentatively called this region mecR. Analysis of selected Mcr strains of Staphylococcus aureus and S. epidermidis by Southern hybridization suggested that the natural occurrence of two types of mec resistance determinants differ by the presence or absence of mecR-specific sequences.
Comparative postantibacterial activities of pefloxacin, ciprofloxacin, and ofloxacin against intracellular multiplication of Legionella pneumophila serogroup 1
Authors: Rajagopalan-Levasseur P , Dournon E , Dameron G , Vilde J L , Pocidalo J J
Published: June 2012

The inhibitory and postantibacterial activities of pefloxacin, ciprofloxacin, and ofloxacin against virulent Legionella pneumophila serogroup 1 were evaluated in cell-free and cellular models. In the absence of macrophages (with the tissue culture medium alone), bacterial numbers remained unchanged at 24 h in the presence of 0.1 microgram of pefloxacin, ciprofloxacin, or ofloxacin per ml and 1.0 microgram of pefloxacin per ml, whereas they were reduced in the presence of 1.0 microgram of ciprofloxacin or ofloxacin per ml. Experiments to evaluate the postantibacterial effects of these drugs were therefore performed with concentrations of 0.1 microgram/ml. In the cell-free model, brief exposure (1 h) of bacteria to each antimicrobial agent resulted in a transient decrease in numbers followed by logarithmic growth. In the cellular model, all three drugs (at 0.1 and 1.0 microgram/ml) inhibited the intracellular multiplication of L. pneumophila. The intracellular postantibacterial effects of 0.1 microgram of pefloxacin, ciprofloxacin, and ofloxacin per ml, which were left in contact with L. pneumophila-infected human macrophages for 24 h, were evaluated at various times after removal of the drugs. Pefloxacin was found to exhibit a significant inhibitory effect at 72 h, whereas following the removal of ciprofloxacin and ofloxacin, rapid bacterial multiplication occurred, leading to the destruction of the macrophage monolayer within 48 h. Thus, while pefloxacin, ciprofloxacin, and ofloxacin all inhibited the multiplication of L. pneumophila in human monocyte-derived macrophages, only pefloxacin exhibited a prolonged postantibacterial effect.
Effects of enoxacin on renal and metabolic clearance of theophylline in rats
Authors: Nadai M , Hasegawa T , Kuzuya T , Muraoka I , Takagi K , Yoshizumi H
Published: June 2012

The effects of enoxacin and its metabolite 4-oxoenoxacin on the disposition of theophylline were investigated in rats. Systemic clearance of theophylline was significantly decreased by approximately 40, 46, and 50% after oral coadministration of 25, 100, and 200 mg of enoxacin per kg, respectively. No significant changes in the volume of distribution of theophylline were observed. 4-Oxoenoxacin had no direct effect on theophylline disposition. Significant changes in urinary excretion of theophylline and its metabolites were observed. (i) Urinary excretion of unchanged theophylline was significantly increased in proportion to increases in enoxacin dosage. (ii) Decreases in renal clearance of theophylline and metabolic clearance of 1-methyluric acid and 1,3-dimethyluric acid were observed. (iii) The percent decreases in the metabolic clearance of 1-methyluric acid were dependent on enoxacin dosage. It is likely that enoxacin inhibits the elimination process, which depends on cytochrome P-450-mediated isozymes for N demethylation and oxidation, and that the capacity of the inhibitory effect of enoxacin is greater in the N-demethylation pathway than it is in oxidation.
Alpha interferon (2b) in combination with zidovudine for the treatment of presymptomatic feline leukemia virus-induced immunodeficiency syndrome
Authors: Zeidner N S , Myles M H , Mathiason-DuBard C K , Dreitz M J , Mullins J I , Hoover E A
Published: June 2012

The therapeutic efficacies of human recombinant alpha interferon (IFN-alpha), IFN-alpha plus zidovudine (AZT), and AZT alone were evaluated in presymptomatic cats with established feline leukemia virus (FeLV)-acquired immunodeficiency syndrome (FAIDS) infection and high levels of persistent antigenemia. Subcutaneous injection of 1.6 x 10(6) U of human recombinant IFN-alpha 2b per kg delivered peak concentrations in plasma of 3,600 U/ml at 2 h postadministration with a half-life of elimination of 2.9 h. This dosage of IFN-alpha could be delivered to cats for up to 12 weeks without significant clinical toxicity. Oral administration of AZT (20 mg/kg three times daily) resulted in peak concentrations in plasma of 3 micrograms/ml at 2 h with a half-life of elimination of approximately 1.60 h. Treatment of FeLV-FAIDS-infected cats with IFN-alpha, either alone or in combination with orally administered AZT, resulted in significant decreases in circulating p27 core antigen beginning 2 weeks after the initiation of therapy. AZT alone had no effect on circulating virus antigen. Depending upon whether high (1.6 x 10(6) U/kg)- or low (1.6 x 10(4) to 1.6 x 10(5) U/kg)-dosage IFN-alpha was used, cats became refractory to therapy 3 or 7 weeks after the beginning of treatment. At these times, IFN-alpha-treated animals developed antibodies to IFN-alpha that were neutralizing, specific for human recombinant IFN-alpha, and dose dependent in magnitude. The results of this study indicate that human recombinant IFN-alpha is effective in reducing circulating virus antigenic load in cats persistently infected with FeLV-FAIDS. However, the continued efficacy of IFN-alpha therapy appeared to be limited by the formation of cytokine-specific neutralizing antibodies.
Cell wall and membrane changes associated with ethambutol resistance in Mycobacterium tuberculosis H37Ra
Authors: Sareen M , Khuller G K
Published: June 2012

Biochemical variations accompanying the acquisition of ethambutol (EMB) resistance in a single-step mutant of Mycobacterium tuberculosis H37Ra were analyzed. Comparative analysis of phospholipids revealed a reduced content in the EMB-resistant strain, particularly in the cell membrane fraction. Significant alterations were observed in the individual phospholipid content and phospholipid fatty acyl group composition of whole cells and subcellular fractions. Quantitative changes were seen in the chemical constituents of the cell walls of resistant cultures in comparison with those of EMB-susceptible cultures of M. tuberculosis. Alterations in the binding of 1-anilinonaphthalene-8-sulfonate to whole cells of an EMB-resistant strain indicated structural changes on the cell surface. Structural changes in the cell wall may play an important role in the resistance of M. tuberculosis H37Ra to EMB.
In vitro activities of 4-quinolones against the fish pathogen Aeromonas salmonicida
Authors: Barnes A C , Lewin C S , Hastings T S , Amyes S G
Published: June 2012

The activities of five fluorinated 4-quinolones, namely, sarafloxacin, enrofloxacin, PD127391, PD117596, and CI934, against the fish pathogen Aeromonas salmonicida were investigated and compared with that of oxolinic acid.The results indicated that with the exception of CI934, these drugs are more active than oxolinic acid in terms of MIC. No inoculum effect was observed, but the drugs were less active at 10 degrees C than at 22 degrees C. The presence of 3% of NaCl caused an increase in drug activity. Resistance to the drugs appeared to be fairly stable, with only a small decrease in activity after 10 successive passages of the test strains on drug-free tryptone soya agar.
Magainin analogs effective against pathogenic protozoa
Authors: Huang C M , Chen H C , Zierdt C H
Published: June 2012

The in vitro activities of magainin analogs against Blastocystis hominis, Entamoeba histolytica, and Trypanosoma cruzi were assessed by protozoan morphological integrity and motility. The antiprotozoan activities in descending order were magainin B greater than G greater than H, the same order as the alpha-helix contents of the analogs. Magainin B and G were effective against B. hominis, T. cruzi, and E. histolytica.
Interaction of the antibiotic sparsomycin with the ribosome
Authors: Lazaro E , San Felix A , van den Broek L A , Ottenheijm H C , Ballesta J P
Published: June 2012

Phenol-alanine-sparsomycin, a derivative of sparsomycin carrying a p-hydroxy-benzyl function easily labeled by iodination, has been used to study the interaction of this drug with the ribosome. Our study indicated that the binding of the drug to the ribosome is sensitive to trichloracetic acid and is equally affected by disintegration of the particle after RNase and protease treatments. The ribosome is not irreversibly inactivated, and the chemical structure of the drug is not affected by interaction with the particle. These data are not compatible with the proposed covalent association of sparsomycin with the ribosome by G. A. Flynn and R. J. Ash (Biochem. Biophys. Res. Commun. 114:1-7, 1983); therefore, the antibiotic must inhibit protein synthesis through a reversible interaction with the ribosome.
First-exposure adaptive resistance to aminoglycoside antibiotics in vivo with meaning for optimal clinical use
Authors: Daikos G L , Lolans V T , Jackson G G
Published: June 2012

The first exposure of gram-negative bacilli to an aminoglycoside antibiotic in vitro induces a biphasic bactericidal response and adaptive drug resistance (G. L. Daikos, G. G. Jackson, V. T. Lolans, and D. M. Livermore, J. Infect. Dis. 162:414-420, 1990; G. G. Jackson, G. L. Daikos, and V. T. Lolans, J. Infect. Dis. 162:408-413, 1990). The therapeutic implications were examined in netilmicin treatment of a Pseudomonas aeruginosa infection of normal and neutropenic mice. For 2 h after the first dose, the bactericidal rates were rapid, 0.75, 1.0, and 1.5 log10 CFU/h with doses of 10, 30, and 60 mg/kg, respectively. Each twofold increase in dosage reduced the number of surviving bacteria fivefold. Between 2 and 6 h, the second-phase bactericidal rate was slow, less than or equal to 0.3 log10 CFU/h, regardless of the dose. In a multiple-dose regimen, the same amount of netilmicin given in one dose was 70 and 90% more effective than two or three doses, respectively. Doses calculated to keep the drug level in plasma above the MIC were less effective than regimens giving first exposure to a high drug concentration. Adaptive resistance occurred when doses were given more than 2 h after the start of treatment. Temporary survival of bacteremic neutropenic mice was 60 to 70% greater with a second dose at 2 h than after a longer interval. In a thigh infection of neutropenic mice treated every 2 h, doses 4, 6, and 8 h after the first one showed no bactericidal effect. A drug-free interval of 8 h (20 times the drug half-life) renewed bacterial susceptibility to drug action. The results in vivo confirm the biphasic bactericidal action and induction of adaptive resistance that characterized first exposure of gram-negative bacilli to aminoglycoside antibiotics. The phenomena have meaning for the optimum clinical use of aminoglycosides.
Antibacterial activities in vitro and in vivo and pharmacokinetics of cefquinome (HR 111V), a new broad-spectrum cephalosporin
Authors: Limbert M , Isert D , Klesel N , Markus A , Seeger K , Seibert G , Schrinner E
Published: June 2012

Cefquinome is a new injectable aminothiazolyl cephalosporin derivative. It is stable against chromosomally and plasmid-encoded beta-lactamases and has a broad antibacterial spectrum. Staphylococcus aureus, streptococci, Pseudomonas aeruginosa, and members of the family Enterobacteriaceae (Escherichia coli, Salmonella spp., Klebsiella spp., Enterobacter spp., Citrobacter spp., and Serratia marcescens) are inhibited at low concentrations. Cefquinome is also active against many strains of methicillin-resistant staphylococci and enterococci. Its in vitro activity against gram-negative anaerobes is very limited. The high in vitro activity of cefquinome is reflected by its high in vivo efficacy against experimental septicemia due to different gram-positive and gram-negative bacteria. We studied the pharmacokinetic properties of cefquinome in mice, dogs, pigs, and calves. After single parenteral administrations, cefquinome displayed high peak levels, declining with half-lives of about 0.5, 0.9, 1.2, and 1.3 h, respectively. The areas under the concentration-time curve determined for dogs and mice showed linear correlations to the given doses. In dogs the urinary recovery was more than 70% within 24 h of dosing.
In vitro antibacterial activities of PD 131628, a new 1,8-naphthyridine anti-infective agent
Authors: Cohen M A , Huband M D , Mailloux G B , Yoder S L , Roland G E , Domagala J M , Heifetz C L
Published: June 2012

PD 131628 is a new aminopyrrolidine-substituted fluorocyclopropyl naphthyridine quinolone which possesses high in vitro activity against a wide spectrum of bacterial species. The MICs for greater than or equal to 90% of strains were 0.125 to 0.25 microgram/ml for staphylococci, Streptococcus pyogenes, and S. pneumoniae; 0.5 micrograms/ml for S. agalactiae and Enterococcus faecalis; 0.125 micrograms/ml for members of the family Enterobacteriaceae and Acinetobacter spp.; 0.5 micrograms/ml for Pseudomonas aeruginosa; and less than or equal to 0.03 micrograms/ml for Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and Neisseria gonorrhoeae. In these in vitro comparisons with ciprofloxacin, PD 131628 is more active against gram-positive organisms, approximately equivalent against gram-negative organisms, and, like most other quinolones, relatively inactive against gram-negative anaerobes. In most instances, the in vitro potency of PD 131628 exceeded those of widely used compounds: ciprofloxacin, imipenem, ampicillin, penicillin G, oxacillin, cefazolin, ceftazidime, cefoxitin, cefsulodin, aztreonam, piperacillin, amikacin, spectinomycin, doxycycline, erythromycin, metronidazole, and vancomycin.
In vitro inactivation of aminoglycosides by sulbactam, other beta-lactams, and sulbactam-beta-lactam combinations
Authors: Fuchs P C , Stickel S , Anderson P H , Barry A L , Shilling S
Published: June 2012

At clinically achievable levels (e.g., 25 micrograms/ml), sulbactam exerted no effect on aminoglycoside concentrations when incubated together in pooled serum at 37 degrees C for up to 24 h. Sulbactam alone and in combination with ampicillin or cefoperazone inactivated tobramycin, gentamicin, netilmicin, and amikacin in vitro when the sulbactam concentration was 200 to 225 micrograms/ml. At 75 micrograms/ml, sulbactam inactivated only tobramycin. Inactivation of tobramycin by high concentrations of sulbactam occurred even at -20 degrees C, but not at -70 degrees C, and was influenced by the serum matrix.
Inducible transfer of conjugative transposon Tn1545 from Enterococcus faecalis to Listeria monocytogenes in the digestive tracts of gnotobiotic mice
Authors: Doucet-Populaire F , Trieu-Cuot P , Dosbaa I , Andremont A , Courvalin P
Published: June 2012

Transfer of conjugative transposon Tn1545 from Enterococcus faecalis to Listeria monocytogenes was studied in vitro and in vivo. Tn1545 transferred following filter mating at a frequency of 2.5 x 10(-7) transconjugants per donor colony. A 20-fold increase in transfer frequency was observed when matings were performed in the presence of a subinhibitory concentration of tetracycline. The frequency of in vivo transfer of Tn1545, expressed as the number of transconjugants per donor cell extracted from the intestines of the gnotobiotic mice after 35 days of experiment, was 1.1 x 10(-8). Presence of a low concentration of tetracycline in the drinking water increased this frequency 10-fold.
Comparative in vitro effects of liposomal amphotericin B, amphotericin B-deoxycholate, and free amphotericin B against fungal strains determined by using MIC and minimal lethal concentration susceptibility studies and time-kill curves
Authors: Ralph E D , Khazindar A M , Barber K R , Grant C W
Published: June 2012

Multilamellar liposomal amphotericin B (L-AmB) was generally less active in vitro against yeast strains than was amphotericin B-deoxycholate or free amphotericin B, although continual agitation of the broth disproportionately increased the activity of L-AmB. Time-kill studies also demonstrated a slower onset of action of L-AmB and supported the hypothesis that liposomes may act as reservoirs for free amphotericin B, which is the active moiety.
In vitro susceptibilities of ocular Bacillus cereus isolates to clindamycin, gentamicin, and vancomycin alone or in combination
Authors: Gigantelli J W , Torres Gomez J , Osato M S
Published: June 2012

A broth dilution assay was used to determine the in vitro susceptibilities of 10 ocular isolates of Bacillus cereus to clindamycin, gentamicin, and vancomycin both alone and in combination. The checkerboard technique was used to determine fractional inhibitory and bactericidal concentration indices for combinations of clindamycin-gentamicin and vancomycin-gentamicin.
In vitro and in vivo activities of LJC10,627, a new carbapenem with stability to dehydropeptidase I
Authors: Petersen P J , Jacobus N V , Weiss W J , Testa R T
Published: June 2012

The activity of LJC10,627 was compared with the activities of imipenem and other antibiotics. LJC10,627 was more active against most members of the family Enterobacteriaceae, Pseudomonas spp., and Acinetobacter spp. but slightly less active than imipenem against staphylococci and streptococci. LJC10,627 showed stability to mouse dehydropeptidase I and was more effective in vivo than imipenem plus cilastatin against gram-negative bacterial infections and as effective against staphylococcal infections.
Structure-activity study of inhibition of amphotericin B (Fungizone) binding to sterols, toxicity to cells, and lethality to mice by esters of sucrose
Authors: Gruda I , Milette D , Brother M , Kobayashi G S , Medoff G , Brajtburg J
Published: June 2012

The effects of four monoesters of sucrose with different acyl chain lengths (palmitate, C16; myristate, C14; laurate, C12; and caprate, C10) on the aggregation state of amphotericin B (AmB), its binding to cholesterol and ergosterol, its toxicity to cells, and its lethality to mice were determined. In solution, all four of these esters inhibited AmB binding to cholesterol more than to ergosterol; this effect correlated with the ester-induced shift from the mainly aggregated form of AmB to the mainly monomeric form. In experiments with cells, the esters inhibited the toxicity of AmB to mouse erythrocytes and cultured mouse fibroblast L-929 cells more than its toxicity to Candida albicans cells. When injected intravenously with AmB, these esters decreased AmB lethality to mice. In all of these assays, the ester with the shortest chain length (caprate) was much less potent than the other three esters. Our results indicate a correlation between in vitro and in vivo assays and suggest that the in vitro and in vivo selectivity of AmB may be enhanced by surface-active agents which modulate the aggregation state of AmB.
Mechanism of action of anticandidal dipeptides containing inhibitors of glucosamine-6-phosphate synthase
Authors: Milewski S , Andruszkiewicz R , Kasprzak L , Mazerski J , Mignini F , Borowski E
Published: June 2012

The mechanism of anticandidal action of novel synthetic dipeptides containing N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP) residues was shown to be consistent with the "warhead delivery" concept. FMDP dipeptides were shown to be transported into Candida albicans cells by the di-tripeptide permease and subsequently hydrolyzed by intracellular peptidases, especially aminopeptidase. The anticandidal activity of the particular FMDP dipeptide was influenced by the rate of its transport and, to a lower extent, by the intracellular cleavage rate. A high transport rate accompanied by a high cleavage rate resulted in the high anticandidal activity of L-norvalyl-FMDP. The strong growth-inhibitory effect of this compound was the consequence of inhibition of the enzyme glucosamine-6-phosphate synthase by the released FMDP. The action of L-norvalyl-FMDP on exponentially growing C. albicans cells resulted in a sharp decrease of incorporation of 14C label from [14C]glucose into chitin, mannoprotein, and glucan. This effect, as well as the growth-inhibitory effect, was fully reversed by exogenous N-acetyl-D-glucosamine. Glucosamine-6-phosphate synthase was proved to be the only essential target for FMDP dipeptides. Scanning electron microscopy of C. albicans cells treated with L-norvalyl-FMDP revealed highly distorted, wrinkled, and collapsed forms. Cells formed long, bulbous chains, and partial lysis occurred.
Cloning and characterization of the isopenicillin N synthase gene of Streptomyces griseus NRRL 3851 and studies of expression and complementation of the cephamycin pathway in Streptomyces clavuligerus
Authors: García-Domínguez M , Liras P , Martín J F
Published: June 2012

A gene, pcbC, encoding the isopenicillin N synthase of Streptomyces griseus NRRL 3851, has been cloned in a 6.4-kb Bg/II DNA fragment and located in an internal 1.55-kb PvuII segment by hybridization with the Penicillium chrysogenum pcbC gene. Hybridization studies revealed the presence of homologous sequences in the DNAs of several Streptomyces strains and Nocardia lactamdurans. The S. griseus pcbC gene was not expressed in Streptomyces lividans but was expressed in Streptomyces clavuligerus and complemented a mutation, nce2, that impaired isopenicillin N synthase and cephamycin biosynthesis. The pcbC gene contained an open reading frame of 990 nucleotides that encodes a protein of 329 amino acids with a deduced Mr of 37,371. The isopenicillin N synthase formed after expression of the pcbC gene in the S. clavuligerus nce2 mutant strain was found to have an Mr of 38,000 by gel filtration. A protein of about 38 kDa was observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels of extracts of a transformant of the nce2 mutant strain; this protein was absent from the untransformed mutant strain. The G+C content of the pcbC gene was 63.6%, and the strongly biased codon usage was typical of that of Streptomyces strains. A transcription initiation site was found 44 nucleotides upstream of the ATG translation initiation triplet. A transcript of 1.1 kb was observed in the donor S. griseus strain and also in the S. clavuligerus nce2 mutant strain transformed with the pcbC gene, suggesting that it is transcribed as a monocistronic mRNA.
W-1 solubilization and kinetics of inhibition by cilofungin of Candida albicans (1,3)-beta-D-glucan synthase
Authors: Tang J , Parr T R
Published: June 2012

(1,3)-beta-D-Glucan synthase of Candida albicans was rendered soluble by treatment of membrane preparations with the polyoxyethylene ether detergent W-1. Extraction with 0.025% W-1 at 4 degrees C for 24 h effectively solubilized and activated the enzyme. Under these conditions, greater than 85% of the protein in membrane preparations was released, and about 64% of the glucan synthase activity could be recovered in the soluble form. Soluble enzyme activity was stable for more than 12 days at 4 degrees C. Also, glucan synthase activity in the extracted membrane preparations could be activated to achieve more than twice the enzyme activity in the original, unextracted membrane preparations. The soluble glucan synthase had characteristics similar to those of the membrane-bound enzyme. Soluble glucan synthase had an apparent Km of 2.0 mM, and particulate glucan synthase had an apparent Km of 2.5 mM. Kinetics of cilofungin inhibition for both enzyme preparations were noncompetitive, with an apparent Ki of 2.5 microM; both preparations could be inhibited by cilofungin but not by its peptide nucleus or side chain, either alone or in combination. The reaction products from both forms of the enzyme were sensitive to (1,3)-beta-D-glucanase degradation but not to alpha-amylase, alpha-glucosidase, or proteinase K degradation and thus were shown to be beta(1----3) glucan.
Microculture screening assay for primary in vitro evaluation of drugs against Pneumocystis carinii
Authors: Comley J C , Mullin R J , Wolfe L A , Hanlon M H , Ferone R
Published: June 2012

Pneumocystis carinii inoculated into 96-well filtration plate assemblies was shown to synthesize radiolabeled folates de novo from [para-3H]aminobenzoic acid ([3H]pABA). At the end of each incubation with [3H]pABA, a vacuum manifold was used to remove the medium and wash P. carinii. The membrane at the base of each well was dried and punched out, and the level of 3H retained was determined by direct scintillation counting. High-pressure liquid chromatography analysis of duplicate filters confirmed that direct counting of 3H retained on membranes (after correction for unmetabolized [3H]pABA) was an accurate reflection of total [3H]pABA incorporation by P. carinii. Greater than 95% of the 3H recovered was shown to be present as polyglutamated species. After digestion with rat plasma folic acid gamma-glutamyl hydrolase, para-aminobenzoylglutamate, N10-formyltetrahydrofolate, and tetrahydrofolate were identified as the major 3H-labeled components. para-Aminobenzoylglutamate was presumed to have arisen from folylpolyglutamates synthesized by P. carinii and was therefore included in the calculation of total [3H]pABA incorporation. P. carinii incorporation of [3H]pABA under optimal conditions was used as a selective measure of in vitro viability against which the inhibitory effects of some antipneumocystis agents (pentamidine, sulfamethoxazole, 566C80, and piritrexim) were quantitated. The concentrations of pentamidine, sulfamethoxazole, 566C80, and piritrexim required for 50% inhibition in this assay were 7.3, 0.1, 1.4, and approximately 100 microM, respectively. The results suggest that this 96-well [3H]pABA incorporation assay has considerable potential for objective in vitro drug screening against P. carinii.
Synergistic inhibition of human immunodeficiency virus type 1 replication in vitro by two-drug and three-drug combinations of 3'-azido-3'-deoxythymidine, phosphonoformate, and 2',3'-dideoxythymidine
Authors: Kong X B , Zhu Q Y , Ruprecht R M , Watanabe K A , Zeidler J M , Gold J W , Polsky B , Armstrong D , Chou T C
Published: June 2012

The effects of 3'-azido-3'-deoxythymidine (AZT), phosphonoformate (PFA), and 2',3'-dideoxythymidine (ddT) and their combination on human immunodeficiency type 1 (HIV-1) replication were studied by measuring the HIV-1 p24 antigen expression and reverse transcriptase (RT) release in HIV-1-infected MT4 cells in vitro. RT activity was also measured in a cell-free system by using poly(rA)-oligo(dT) as the primer-template, and cell growth inhibition was measured in noninfected MT4 cells. The interactions of these two- and three-drug combinations were evaluated by the combination index (CI) method and isobologram techniques. The 50% effective concentrations (EC50s) of AZT, PFA, and ddT were 0.014 to 0.005, 9.4 to 8.8, and 8.4 to 2.5 microM, respectively, for p24 enzyme-linked immunosorbent assays (ELISAs) and 0.005 to 0.0034, 1.43 to 1.37, and 2.87 to 2.83 microM, respectively, for RT activity in vitro; for RT activity in the cell-free system, the EC50s were 0.00019 to 0.00024, 0.012 to 0.02, and 0.00074 to 0.0005 microM, for AZT-5'-triphosphate, PFA, and ddT-5'-triphosphate, respectively. AZT in combination with PFA (1:200) or ddT (1:5) as well as the combination of these three drugs (1:200:5) synergistically inhibited HIV-1 replication and RT activity in the cell-free system over a wide range of drug concentrations, with the CIs ranging from 0.5 to 0.09, in which CIs of less than 1, 1, and greater than 1 indicate synergism, additive effect, and antagonism, respectively. Three- and two-drug combinations of AZT, PFA, and ddT showed similar degrees of synergism against HIV-1 replication in p24 assays and RT release assays, whereas the combination of AZT and ddT was found to be the most selective in terms of its anti-HIV-1 effect versus cytotoxicity. Dose reduction indices calculated from both HIV-1 replication inhibition, as measured by p24 ELISA and by RT activity in the cell-free system, indicated that two- and three-drug combinations at high effect levels and the selected combination ratios allow 2- to 240-fold dose reduction over the single drug alone in terms of their anti-HIV-1 effects. The three-drug combination showed the highest dose reduction index. These finding suggest that increased efficacy and reduced toxicity may be achieved in AIDS therapy by using AZT, PFA, and ddT in two- or three-drug combinations.
Use of ampicillin-sulbactam for treatment of experimental meningitis caused by a beta-lactamase-producing strain of Escherichia coli K-1
Authors: Guerra-Romero L , Kennedy S L , Fournier M A , Tureen J H , Täuber M G
Published: June 2012

We evaluated the pharmacokinetics and therapeutic efficacy of ampicillin combined with sulbactam in a rabbit model of meningitis due to a beta-lactamase-producing strain of Escherichia coli K-1. Ceftriaxone was used as a comparison drug. The MIC and MBC were 32 and greater than 64 micrograms/ml (ampicillin), greater than 256 and greater than 256 micrograms/ml (sulbactam), 2.0 and 4.0 micrograms/ml (ampicillin-sulbactam [2:1 ratio, ampicillin concentration]) and 0.125 and 0.25 micrograms/ml (ceftriaxone). All antibiotics were given by intravenous bolus injection in a number of dosing regimens. Ampicillin and sulbactam achieved high concentrations in cerebrospinal fluid (CSF) with higher dose regimens, but only moderate bactericidal activity compared with that of ceftriaxone was obtained. CSF bacterial titers were reduced by 0.6 +/- 0.3 log10 CFU/ml/h with the highest ampicillin-sulbactam dose used (500 and 500 mg/kg of body weight, two doses). This was similar to the bactericidal activity achieved by low-dose ceftriaxone (10 mg/kg), while a higher ceftriaxone dose (100 mg/kg) produced a significant increase in bactericidal activity (1.1 +/- 0.4 log10 CFU/ml/h). It appears that ampicillin-sulbactam, despite favorable CSF pharmacokinetics in animals with meningitis, may be of limited value in the treatment of difficult-to-treat beta-lactamase-producing bacteria, against which the combination shows only moderate in vitro activity.
Pharmacokinetics of cefuroxime axetil suspension in infants and children
Authors: Powell D A , James N C , Ossi M J , Nahata M C , Donn K H
Published: June 2012

The pharmacokinetics of cefuroxime axetil suspension in 28 infants and children, ranging in age from 3 months to 12 years (mean, 23 months), were studied. Mean maximum serum cefuroxime concentrations of 3.3, 5.1, and 7.0 micrograms/ml were achieved 3.6, 2.7, and 3.1 h after the administration of doses of 10, 15, and 20 mg, respectively, of cefuroxime axetil suspension per kg of body weight together with milk or milk formula. These concentrations exceed the MICs for common respiratory tract pathogens, including beta-lactamase-producing strains of Haemophilus influenzae and Moraxella (Branhamella) catarrhalis. Following a 10- or 15-mg/kg dose, serum cefuroxime concentrations are similar to those achieved in adults following the administration of a 250-mg cefuroxime axetil tablet. There were linear relationships between dose and both maximum serum cefuroxime concentration and area under the serum drug concentration-verus-time curve. The mean half-life of cefuroxime in serum was independent of dose and ranged from 1.4 to 1.9 h. No cefuroxime axetil (intact ester) was detected in the blood. The intact ester in the urine of four children was measured; however, the amount recovered represented less than 0.1% of the administered dose.
Single-dose pharmacokinetics of ceftibuten (SCH 39720) in infants and children
Authors: Kearns G L , Reed M D , Jacobs R F , Ardite M , Yogev R D , Blumer J L
Published: June 2012

Ceftibuten (CFB), a new broad-spectrum cephalosporin for oral administration, possesses potent activity in vitro against a wide range of gram-negative and certain gram-positive pathogens frequently encountered in pediatric patients. Its antimicrobial spectrum and dosage formulation suggest a use for CFB in the treatment of otitis media and upper and lower respiratory and urinary tract infections in infants and children. To assess the pharmacokinetic characteristics of CFB in pediatric patients, we completed a multicenter investigation of 49 children (26 females) between the ages of 6 months and 17 years who had normal hepatic and renal functions and no evidence of chronic disease. Pharmacokinetic parameters were determined from repeated blood samples (n = 12) and, when possible, quantitative urine collections (n = 7) obtained over a 12- to 24-h period following a single oral CFB dose of either 4.5 or 9.0 mg/kg of body weight. CFB was quantitated from plasma and urine samples by using a sensitive, microanalytical high-pressure liquid chromatography method. The drug was rapidly absorbed (mean time to maximum concentration in serum = 140 min) and produced apparent peak concentrations in plasma (Cmax) ranging from 5.0 to 19.0 mg/liter. Average CFB pharmacokinetic parameters (+/- standard deviations) were as follows: apparent elimination half-life, 2.0 +/- 0.5 h; mean residence time, 3.9 +/- 1.1 h; apparent steady-state volume of distribution, 0.4 +/- 0.2 liter/kg; and apparent total plasma clearance (CL/F), 2.5 +/- 0.9 ml/min/kg. No significant differences in any of the pharmacokinetic parameters were observed between the two dosing groups. Significant (P < 0.05) negative correlations were found between patient age and CFB elimination half-life and CL/F and between the estimated creatinine clearance and renal clearance and CL/F. Apparent age dependence of CFB disposition was also reflected by a greater CL/F in children from 0.5 to less than or equal 5 years of age (3.1 +/- 1.1 ml/min/kg) than in children > 10 years of age (2.0 +/- 0.6 ml/min/kg; P < 0.005). The increased CL/f for CFB (3.0 +/- 0.5 ml/min/kg) was corroborated by a validation study performed with 11 infants (1.0 +/- 0.5 ml/min/kg) with CL/F for 19 subjects suggested that appreciable nonrenal clearance (1.3 +/- 0.6 ml/min/kg) of CFB occurred in children, a finding different from preliminary data for adults.
Anabolic pathway of 6-methoxypurine arabinoside in cells infected with varicella-zoster virus
Authors: de Miranda P , Burnette T C , Biron K K , Miller R L , Averett D R , Krenitsky T A
Published: June 2012

6-Methoxypurine arabinoside (ara-M) exhibits potent activity against varicella-zoster virus (VZV) as a result of ara-M's anabolism to the triphosphate of adenine arabinoside (ara-ATP) in VZV-infected cells. The adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) enhanced the formation of ara-ATP by inhibiting ara-M demethoxylation. In contrast, deoxycoformycin and coformycin, inhibitors of both adenosine deaminase and AMP deaminase, blocked the formation of ara-ATP and reversed the anti-VZV activity of ara-M. These results indicate that after the initial phosphorylation of ara-M by the VZV-coded thymidine kinase, the monophosphate is demethoxylated by AMP deaminase to form ara-IMP, which is converted to ara-ATP by the sequential actions of the cellular adenylosuccinate synthetase, adenylosuccinate lyase, and nucleotide kinases.
Ciprofloxacin resistance in coagulase-positive and -negative staphylococci: role of mutations at serine 84 in the DNA gyrase A protein of Staphylococcus aureus and Staphylococcus epidermidis
Authors: Sreedharan S , Peterson L R , Fisher L M
Published: June 2012

gyrA mutations in quinolone-resistant pathogenic isolates of Staphylococcus spp. have been detected by the direct HinfI digestion of polymerase chain reaction products. Homology among gyrA genes allowed rapid examination of both coagulase-positive and -negative isolates. DNA sequence analysis revealed that ciprofloxacin resistance in Staphylococcus epidermidis is associated with a novel Ser-84----Phe mutation in the DNA gyrase A protein, analogous to Ser-84----Leu changes observed in Staphylococcus aureus.
Increased resistance to multiple drugs by introduction of the Enterobacter cloacae romA gene into OmpF porin-deficient mutants of Escherichia coli K-12
Authors: Komatsu T , Ohta M , Kido N , Arakawa Y , Ito H , Kato N
Published: June 2012

Introduction of the romA gene cloned from Enterobacter cloacae into Escherichia coli K-12 resulted in almost complete inhibition of OmpF expression and a concomitant increase in resistance to quinolones, beta-lactams, chloramphenicol, and tetracyclines. In addition, the romA gene reduced the susceptibility to these multiple drugs even in the OmpF porin-deficient mutants of E. coli K-12. Results indicate the presence of romA-sensitive penetration pathway(s) for these multiple drugs other than the OmpF porin in E. coli.
Brugia malayi and Acanthocheilonema viteae: antifilarial activity of transglutaminase inhibitors in vitro
Authors: Rao U R , Mehta K , Subrahmanyam D , Vickery A C
Published: June 2012

The possible involvement of transglutaminase-catalyzed reactions in survival of adult worms, microfilariae (mf), and infective larvae of the filarial parasite Brugia malayi was studied in vitro by using the specific pseudosubstrate monodansylcadaverine (MDC) and the active-site inhibitors cystamine or iodoacetamide. These inhibitors significantly inhibited parasite mobility in a dose-dependent manner. This inhibition was associated with irreversible biochemical lesions followed by filarial death. A structurally related, inactive analog of MDC, dimethyldansylcadaverine, did not affect the mobility or survival of the parasites. Adult worms failed to release mf when they were incubated in the presence of MDC or cystamine, and this inhibitory effect on mf release was concentration dependent. Similar embryostatic and macrofilaricidal effects of MDC were observed in Acanthocheilonema viteae adult worms. These studies suggest that transglutaminase-catalyzed reactions may play an important role in the growth, development, and survival of filarial parasites.