bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple assay to screen for inhibitors of interaction between the human immunodeficiency virus envelope glycoprotein and its cellular receptor, CD4
Authors: Chams V , Idziorek T , Maddon P J , Klatzmann D
Published: June 2012

The binding of the human immunodeficiency virus envelope glycoprotein gp120 to the CD4 molecule is the initial step in the viral replicative cycle. This interaction is therefore an important target for therapeutic intervention for the treatment of human immunodeficiency virus infection. We designed an enzyme-linked immunosorbent assay which detects the interaction between recombinant soluble forms of CD4 and gp160. This assay could be used as an initial screen of libraries of synthetic chemical compounds and natural products.
In vitro evaluation of activities of azithromycin, erythromycin, and tetracycline against Chlamydia trachomatis and Chlamydia pneumoniae
Authors: Welsh L E , Gaydos C A , Quinn T C
Published: June 2012

The in vitro activities of azithromycin (CP-62,993; Pfizer), erythromycin, and tetracycline were evaluated by inhibiting Chlamydia trachomatis and Chlamydia pneumoniae, formerly TWAR, propagation in vitro in McCoy cells, HeLa cells, and HL cells. Eleven clinical isolates of C. trachomatis (serovars D, E, F, J, K, and L2) and four strains of C. pneumoniae were tested with an inoculum of 10(3) inclusion-forming units in a 96-well microtiter plate. The MIC ranges of these antimicrobial agents against C. trachomatis were as follows: azithromycin, 0.125 to 0.5 microgram/ml; erythromycin, 0.25 to 0.1 microgram/ml; and tetracycline, 0.0625 to 1.0 microgram/ml. The MBC ranges, calculated from passage into antibiotic-free medium, were as follows: azithromycin, 0.125 to 4.0 micrograms/ml; erythromycin, 0.5 to 8.0 micrograms/ml; and tetracycline, 0.0625 to 4.0 micrograms/ml. The MIC ranges for C. pneumoniae in both HeLa and HL cells were as follows: azithromycin, 0.125 to 1.0 micrograms/ml; erythromycin, 0.0625 to 1.0 microgram/ml; and tetracycline, 0.125 to 1.0 microgram/ml. The MBC ranges were as follows: azithromycin, 0.25 to 1.0 microgram/ml; erythromycin, 0.25 to 1.0 microgram/ml; and tetracycline, 0.125 to 4.0 micrograms/ml. From the results of this in vitro study, azithromycin appears to be an effective antibiotic comparable to tetracycline and erythromycin for use in the treatment of both C. trachomatis and C. pneumoniae infections.
A model of cefoperazone tissue penetration: diffusion coefficient and protein binding
Authors: Meulemans A
Published: June 2012

The apparent diffusion coefficient of a bound drug, cefoperazone, was studied. The protein binding of cefoperazone was studied by voltammetry, a technique which permitted instant measurements. The apparent diffusion coefficients were similar in agar and fibrin and lower in rat brain tissue. The influence of protein on the value of the apparent diffusion coefficient was negligible. The hypothesis that only the free drug diffuses was supported. The percentage of binding determined by voltammetry corresponded to the true concentration of drug which diffuses and is much lower than the percentage of binding determined by the ultrafiltration centrifugation method. This discrepancy could be explained by the rate of dissociation of the protein-drug complex.
Glycosylation of macrolide antibiotics in extracts of Streptomyces lividans
Authors: Cundliffe E
Published: June 2012

Inducible resistance to macrolide antibiotics in Streptomyces lividans involves MGT, a macrolide glycosyl transferase that utilizes UDP-glucose as cofactor. Substrates for MGT include macrolides with 12-, 14-, 15-, or 16-atom cyclic polyketide lactones (as in methymycin, erythromycin, azithromycin, or tylosin, respectively), although spiramycin and carbomycin are not apparently modified. The enzyme is specific for the 2'-OH group of saccharidic moieties attached to C-5 of the 16-atom lactone ring (corresponding to C-5 or C-3 in 14- or 12-atom lactones, respectively).
Study of the parameters of binding of R 61837 to human rhinovirus 9 and immunobiochemical evidence of capsid-stabilizing activity of the compound
Authors: Moeremans M , De Raeymaeker M , Daneels G , De Brabander M , Aerts F , Janssen C , Andries K
Published: June 2012

The binding of the antiviral compound R 61837 to human rhinovirus 9 (HRV 9) was studied quantitatively and compared with binding of R 61837 to HRV 9H, a semiresistant variant. For both strains, radiolabelled R 61387 bound to native particles only. The Kd values obtained by Scatchard analysis of saturation binding data were 37 nM for HRV 9 and 172 nM for HRV 9H, whereas the concentrations resulting in a 50% reduction of cytopathic effect were 42 nM and 840 nM, respectively. Reversibility experiments showed that 65% of the compound could be extracted with chloroform from HRV 9H but less than 5% could be extracted from HRV 9. Dissociation studies demonstrated that in the presence of excess unlabelled compound, the half-lives of the virus compound complex HRV 9 and HRV 9H were 385 and 15 min, respectively. The effect of this antirhinoviral compound on the formation of subviral particles induced by low pH or heat was also investigated. Rate zonal centrifugation experiments using [35S]methionine-labelled HRV 9 showed that binding of R 61837 protected the virus against heat (56 degrees C) and acid (pH 5.0) and that at the same concentration of R 61837 the semiresistant strain was stabilized to a lesser extent. This observation was confirmed immunochemically with nonneutralizing and neutralizing monoclonal antibodies. Both 80S and 130S subviral particles have C antigenic determinants, whereas native particles (150S) have been designated D. R 61837 prevented the switch from D to C antigenicity which can be induced by exposure of rhinoviruses to mild denaturing conditions. These findings indicate that the compound is able to prevent a conformational change of the capsid which may be a prerequisite for infection.
Survey of methicillin-resistant clinical strains of coagulase-negative staphylococci for mecA gene distribution
Authors: Suzuki E , Hiramatsu K , Yokota T
Published: June 2012

A total number of 125 methicillin-resistant (MIC, greater than or equal to 16) coagulase-negative Staphylococcus strains isolated in Japan were surveyed for the distribution of the mecA gene, the structural gene for penicillin-binding protein 2', which is the causative genetic element for the intrinsic resistance of methicillin-resistant Staphylococcus aureus. Screening with colony hybridization by using a cloned mecA gene probe revealed that 121 strains (96.8%) belonging to the nine coagulase-negative Staphylococcus species (S. epidermidis, S. haemolyticus, S. saprophyticus, S. sciuri, S. simulans, S. hominis, S. capitis, S. warneri, and S. caprae) carried mecA in their genome, indicating wide distribution of the gene among coagulase-negative Staphylococcus species. Most (93.4%) of the mecA-carrying strains were producers of penicillinase. Four strains, including two S. haemolyticus and two S. saprophyticus strains, did not carry mecA in spite of their resistance to methicillin. One of them was of low-level resistance (MIC, 16), but three of them had moderate- to high-level resistance to methicillin (MIC, 64). Analysis of gel electrophoretic banding patterns of penicillin-binding proteins of these strains showed absence of penicillin-binding protein 2' but some alterations in signal intensities of the other penicillin-binding proteins. The result indicated that about 3% of methicillin-resistant coagulase-negative staphylococci in these hospitals had a resistance mechanism different from that associated with the production of penicillin-binding protein 2', as has been reported in the case of a borderline methicillin-resistant strain of S. aureus.
Antimicrobial activity of MDL 62,873, a semisynthetic derivative of teicoplanin, in vitro and in experimental infections
Authors: Berti M , Candiani G , Borgonovi M , Landini P , Ripamonti F , Scotti R , Cavenaghi L , Denaro M , Goldstein B P
Published: June 2012

MDL 62,873 is an amide derivative of teicoplanin A2-2. Like those of natural glycopeptides, its antibacterial activity is mediated by inhibition of cell wall peptidoglycan synthesis. Against streptococci and enterococci, the in vitro activity of MDL 62,873 was similar to that of teicoplanin and greater than that of vancomycin. Against staphylococci, it has activity similar to that of vancomycin, and it was significantly more active than teicoplanin against coagulase-negative isolates. Like teicoplanin and vancomycin, MDL 62,873 had slow but significant bactericidal activity (99 to 99.9% killing in 24 h) against staphylococci at concentrations near the MIC. In murine septicemia studies with Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus pneumoniae, the 50% effective doses were lower than those of vancomycin. In staphylococcal endocarditis in rats, MDL 62,873 at 20 mg/kg of body weight and vancomycin at 40 mg/kg, both doses given intravenously twice daily, had similar efficacies in reducing the heart bacterial load. These results probably reflect the longer half-life of MDL 62,873, which has a pharmacokinetic profile in rats similar to that of teicoplanin.
Pharmacokinetic disposition and bactericidal activities of cefepime, ceftazidime, and cefoperazone in serum and blister fluid
Authors: Kalman D , Barriere S L , Johnson B L
Published: June 2012

Cefepime is a new broad-spectrum cephalosporin with excellent gram-positive and gram-negative activity including activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacter cloacae. The pharmacokinetic disposition of cefepime is similar to that of ceftazidime. We compared the pharmacokinetic characteristics and the extent and duration of bactericidal activity in serum and suction-induced blister fluid after single 2-g intravenous doses of cefepime, ceftazidime, and cefoperazone given to healthy subjects. One clinical isolate each of E. cloacae, P. aeruginosa, and S. aureus was used to assess bactericidal activity. Results of the pharmacokinetic analysis were similar to previously reported data for these drugs. The high serum protein binding of cefoperazone (approximately 90%) contributed to poor blister fluid penetration. The other drugs penetrated well into this fluid compartment. Cefepime showed significantly greater bactericidal activity in serum and blister fluid against E. cloacae than the other study drugs, ceftazidime was significantly better in serum and blister fluid against P. aeruginosa, and cefoperazone was significantly better against S. aureus only in serum. None of the study drugs had significant bactericidal activity in blister fluid against S. aureus. Cefepime is a promising antimicrobial agent for the treatment of infections due to E. cloacae.
Efficacy of ticarcillin-clavulanic acid for treatment of experimental Staphylococcus aureus endocarditis in rats
Authors: Catherall E J , Gillon V , Hurn S , Irwin R , Mizen L
Published: June 2012

The efficacy of ticarcillin-clavulanic acid was compared with the efficacies of standard antistaphylococcal agents (flucloxacillin, oxacillin, nafcillin, and vancomycin) and ticarcillin in an experimental model of Staphylococcus aureus endocarditis. Therapy was either initiated soon (8 h) after infection, when numbers of bacteria in aortic valve vegetations were relatively low (approximately 6 to 8 log10 CFU/g), or delayed until 24 h after infection, when the vegetations usually contained greater than 9 log10 CFU/g. Doses of the antibiotic were selected to produce peak concentrations in rat serum similar to those achievable in humans after administration of parenteral therapeutic doses. Ticarcillin-clavulanic acid was more effective overall than ticarcillin alone against endocarditis caused by beta-lactamase-producing strains of S. aureus, illustrating the beta-lactamase-inhibitory activity of clavulanic acid in vivo. Ticarcillin-clavulanic acid was as effective as the standard antistaphylococcal beta-lactam agents flucloxacillin, oxacillin, and nafcillin in these infections, whereas vancomycin was generally less active. These results illustrate the clinical potential of ticarcillin-clavulanic acid in the prophylaxis or therapy of severe staphylococcal infections.
Identification of a ROB-1 beta-lactamase in Haemophilus ducreyi
Authors: Maclean I W , Slaney L , Juteau J M , Levesque R C , Albritton W L , Ronald A R
Published: June 2012

A collection of 100 clinical isolates of Haemophilus ducreyi from Thailand were all found to harbor a 5.4-kb plasmid, designated pTH126, which was shown to contain the bla ROB-1 gene. Restriction enzyme analysis and DNA-DNA hybridization studies confirmed that pTH126 was similar to the ROB-1 beta-lactamase plasmid pVM105 from Actinobacillus pleuropneumoniae. In approximately one-half of the isolates, pTH126 was found together with pHD131, which mediates TEM-1 beta-lactamase production.
Effect of cyclodextrin on the pharmacology of antifungal oral azoles
Authors: Hostetler J S , Hanson L H , Stevens D A
Published: June 2012

Concentrations of oral azoles in serum were compared in a single-dose pharmacologic study in mice. When hydroxypropyl-beta-cyclodextrin was used as a carrier and compared with a standard carrier, polyethylene glycol, drug concentrations determined by bioassay showed that the peak concentration and area under the concentration-time curve were greatly enhanced for itraconazole and saperconazole; moderately enhanced for ketoconazole; but negligibly affected for fluconazole, miconazole, and SCH 42427.
Cytotoxicity of acridine compounds for Leishmania promastigotes in vitro
Authors: Werbovetz K A , Lehnert E K , Macdonald T L , Pearson R D
Published: June 2012

The effect of mammalian and bacterial topoisomerase II inhibitors on Leishmania promastigotes was studied in vitro. Parasites were incubated with drugs, and cytotoxicity was assessed on the basis of the loss of flagellar motility and cell lysis after 48 h. 9-Aminoacridines, which are structurally related to the known antileishmanial compounds quinacrine and chlorpromazine, showed activity against the parasite at concentrations in the range of 10 to 20 microM. Adriamycin showed far less activity, while etoposide and several quinolones were inactive at 100-microM concentrations. These results demonstrate that a particular structural class of compounds is cytotoxic to Leishmania species. The unique structure-activity relationship discovered suggests that leishmanial topoisomerase II could be a useful target for chemotherapy.
Pharmacokinetics of cefepime after single and multiple intravenous administrations in healthy subjects
Authors: Barbhaiya R H , Forgue S T , Gleason C R , Knupp C A , Pittman K A , Weidler D J , Movahhed H , Tenney J , Martin R R
Published: June 2012

The pharmacokinetics of cefepime in 31 young, healthy volunteers were assessed after the administration of single and multiple 250-, 500-, 1,000-, or 2,000-mg intravenous doses. Each subject received a single dose of cefepime via a 30-min intravenous infusion on day 1 of the study. Starting from day 2, subjects received multiple doses of cefepime every 8 h for 9 days, and on the morning of day 11, they received the last dose. Serial blood and urine samples were collected after administration of the first dose and on days 1, 6, and 11. Cefepime concentrations in plasma and urine were assayed by using reverse-phase high-performance liquid chromatography with UV detection. Data were evaluated by noncompartmental methods to determine pharmacokinetic parameters. The mean half-life of cefepime was approximately 2 h and did not vary with the dose or duration of dosing. The regression analyses of peak levels (Cmax) in plasma at the end of the 30-min intravenous infusion and the area under the plasma concentration-versus-time curve (AUCo-infinity) showed a dose-proportional response. The steady-state volume of distribution (Vss) was approximately 18 liters and was independent of the administered dose. The multiple-dose pharmacokinetic data are suggestive of a lack of accumulation or change in clearance of cefepime on repeated dosing. Cefepime was excreted primarily unchanged in urine. The recovery of intact cefepime in urine was invariant with respect to the dose and accounted for over 80% of the dose. The values for renal clearance ranged from 99 to 132 ml/min and were suggestive of glomerular filtration as the primary excretion mechanism. It is concluded that cefepime linear pharmacokinetics in healthy subjects.
Autolysis of methicillin-resistant and -susceptible Staphylococcus aureus
Authors: Gustafson J E , Berger-Bächi B , Strässle A , Wilkinson B J
Published: June 2012

The autolytic activities, including unstimulated, Triton X-100-stimulated, and daptomycin-induced, of various sets of methicillin-resistant and related methicillin-susceptible strains were compared. Faster rates of autolysis were noted in two heterogeneous methicillin-resistant transductants than in their methicillin-susceptible parental recipients, in a heterogeneous resistant strain than in a susceptible derivative created by chemical mutagenesis, and in a homogeneous resistant strain than in a derivative that had decreased methicillin resistance and was created by transposon Tn551 mutagenesis. These results suggest that the presence of the methicillin resistance region, mec, either directly or indirectly through an interaction with other host genes, confers a faster rate of autolysis on strains. Various auxilliary genes are known to affect methicillin resistance expression, and one of these genes, femA, was necessary for the expression of this faster rate of autolysis. These differences in autolytic activities were not observed in isolated crude cell walls retaining autolytic activities, suggesting different modes of regulation of autolysins in intact cells and isolated walls. In contrast, one homogeneous, highly resistant strain, DU4916, had a lower autolytic activity than did derived heterogeneous resistant and susceptible strains created by chemical mutagenesis and a strain that had decreased resistance and was created by transposon mutagenesis. Our observations suggest that methicillin resistance expression is associated with an enhanced rate of autolysis, in heterogeneous resistant strains at least.
Identification and cloning of a tetracycline resistance gene from the fish pathogen Vibrio salmonicida
Authors: Sørum H , Roberts M C , Crosa J H
Published: June 2012

Vibrio salmonicida is the causative agent of cold-water vibriosis in farmed Atlantic salmon. We cloned a 6.9-kb PstI fragment from the 170-MDa plasmid (pRVS1) containing a tetracycline resistance determinant. A subcloned 1.96-kb HindIII fragment was found to mediate the tetracycline resistance. The 2.5-kb ClaI-PvuI fragment carrying the Tet E determinant from Escherichia coli hybridized under stringent conditions with the cloned 1.96-kb HindIII fragment from V. salmonicida. The 1.96-kb HindIII fragment codes for a protein of 26.5 kDa which represents a candidate for the structural TetA protein of the class E determinant. Deletion of a 0.28-kb BalI fragment from the middle of the HindIII fragment resulted in the loss of tetracycline resistance. We were able to show that when E. coli carries the cloned 6.9-kb PstI fragment, expression of tetracycline resistance is regulated by the concentration of tetracycline in the medium. In contrast, tetracycline resistance was constitutively expressed in the E. coli isolate carrying the 1.96-kb HindIII fragment. The tetracycline resistance gene isolated from the 170-MDa R plasmid of the marine fish pathogen V. salmonicida was characterized and shown to be a class E determinant.
Inducible expression of ribosomal clindamycin resistance in Bacteroides vulgatus
Authors: Reig M , Fernández M C , Ballesta J P , Baquero F
Published: June 2012

The abilities of erythromycin and clindamycin to act as inducers of clindamycin resistance in the strain Bacteroides vulgatus RYC18F6 is evaluated in vivo (efficiency of plating of inhibitory clindamycin concentrations) and in vitro [efficiency of poly(U)-directed polypeptide synthesis by ribosomes]. Uninduced cells failed to grow during the first 72 h, even at a very low clindamycin concentration (0.1 microgram/ml); after induction with erythromycin or clindamycin, cells were able to form colonies at 32 micrograms/ml after 48 h. The in vitro polymerization test with B. vulgatus RYC18F6 ribosomes (S-30 extract) showed that ribosomes from uninduced cells were fully sensitive to the inhibitory effect of clindamycin. Ribosomes obtained from erythromycin- or clindamycin-induced cells presented a reduced sensitivity to clindamycin inhibition. These results show that resistance to clindamycin in B. vulgatus RYC18F6 is an inducible phenomenon involving a ribosomal modification, probably similar to that previously described for gram-positive bacteria.
Effects of immunoglobulin G and low-dose amphotericin B on Candida albicans infections in burned mice
Authors: Neely A N , Holder I A
Published: June 2012

Candidiasis causes serious problems for compromised hosts. Effective treatments for Candida albicans infections are few. To see if immunoglobulin (Ig) therapy could be beneficial, burn-immunocompromised mice were treated intravenously with 2.5 mg of five different IgG preparations 48 h postburn and post-C. albicans challenge. Despite up to fourfold differences in titer (1:1,600 to 1:6,400) to C. albicans, all preparations improved 10-day survival about 30% (P less than 0.0001). Treatment with a low dose of amphotericin B (AmB; 0.09 mg/kg of body weight) intravenously 24 and 48 h after burn and challenge improved survival 9 to 45% (P less than 0.0001). Treatment with a low dose of AmB plus IgG showed the same results as treatment with AmB alone and better results than treatment with IgG alone. Quantitative renal cultures from burned mice treated with AmB plus one IgG preparation, Sandoglobulin, showed that C. albicans counts decreased in sham-treated mice from 7.21 +/- 0.15 log10 CFU/g (mean +/- standard error of the mean) to 5.31 +/- 0.34, which was significantly less than counts with AmB (6.11 +/- 0.35) or Sandoglobulin (6.39 +/- 0.18) treatment alone. We conclude that (i) by using decreases in mortality and in renal fungal load as end points, treatment with IgG preparations alone or with a low dose of AmB alone protected burn-immunocompromised mice from candidiasis; (ii) though AmB plus one IgG preparation significantly decreased renal fungal load, the combination did not significantly decrease mortality beyond that found with AmB alone; and (iii) survival data did not correlate with IgG titers to C. albicans.
In vitro and in vivo antibacterial activities of levofloxacin (l-ofloxacin), an optically active ofloxacin
Authors: Fu K P , Lafredo S C , Foleno B , Isaacson D M , Barrett J F , Tobia A J , Rosenthale M E
Published: June 2012

The antibacterial activity of levofloxacin was compared with those of ofloxacin, ciprofloxacin, and other antibiotics. In general, levofloxacin was equally active or up to fourfold more active than ofloxacin against all 801 organisms tested. Levofloxacin was twofold [corrected] more active than ciprofloxacin against Streptococcus pneumoniae and 2- to 4-fold more active than ciprofloxacin against Staphylococcus aureus, Xanthomonas maltophilia, and Bacteroides fragilis. Levofloxacin was two- to eightfold more active than ciprofloxacin against coagulase-negative staphylococci and Acinetobacter spp., although these improvements in potency may not be clinically relevant. Levofloxacin inhibited 90% of streptococci when it was used at concentrations of 1 to 2 micrograms/ml. Levofloxacin was two- to fourfold less active than ciprofloxacin against most members of the family Enterobacteriaceae, such as Escherichia coli; Klebsiella pneumoniae; Citrobacter, Proteus, Providencia, Salmonella, and Yersinia spp.; and Pseudomonas aeruginosa. Both compounds were equally active against Pseudomonas cepacia. The in vitro DNA gyrase inhibitory activity of levofloxacin was as potent as that of ciprofloxacin, with a 50% inhibitory concentration of 0.65 micrograms/ml against an E. coli enzyme. In vivo, oral treatment with levofloxacin was as efficacious or more efficacious than that with ciprofloxacin in systemic as well as pyelonephritis infections in mice. Levofloxacin achieved higher concentrations in the serum and tissue of mice than did ciprofloxacin. This study presents some potential advantages of the pure L isomer of ofloxacin over ciprofloxacin and other quinolones.
Lack of effect of carbonyl cyanide m-chlorophenylhydrazone on KB-5246 accumulation by Staphylococcus aureus
Authors: Kotera Y , Inoue Y , Ohashi M , Ito K , Inoue M
Published: June 2012

The accumulation of KB-5246 in a quinolone-susceptible strain of Staphylococcus aureus was about 70 times that of norfloxacin. Carbonyl cyanide m-chlorophenylhydrazone increased the accumulation of norfloxacin about eightfold, but it did not influence that of KB-5246. The low efflux of KB-5246 from S. aureus may contribute to its potent antibacterial activity.
Relative beta-lactamase- and transpeptidase-inhibitory activities of the new quinolone WIN-57273 in Staphylococcus aureus
Authors: Furet Y X , Lucain C , Pechère J C
Published: June 2012

The new quinolone WIN-57273 was shown to inhibit Staphylococcus aureus beta-lactamase activity noncompetitively in vitro with an apparent Ki value of 0.5 mM. MICs of penicillin G for a highly quinolone-resistant, beta-lactamase-negative strain in the presence of exogenous beta-lactamase decreased considerably when subinhibitory concentrations of WIN-57273 were added. Furthermore, the attachment transpeptidase reaction, investigated on whole cells of S. aureus, was impeded by WIN-57273 concentrations of greater than or equal to 30 microM. While these interactions suggest a novel mechanism of action for this compound, they are probably not relevant to the overall antibacterial potency of WIN-57273.
Effects of amino acids on expression of enterococcal vancomycin resistance
Authors: Zarlenga L J , Gilmore M S , Sahm D F
Published: June 2012

The effects of various amino acids on vancomycin MICs obtained with resistant enterococci was investigated by using broth dilution testing. For both the type A (i.e., possessing transferable resistance to teicoplanin and vancomycin) and the type B (i.e., possessing teicoplanin susceptibility and nontransferable vancomycin resistance) resistant strains, vancomycin MICs in the presence of glycine were substantially lower than those in unsupplemented broth (range of MIC decrease, 8- to 128-fold). No such effect was seen with Enterococcus gallinarum AIB-39 or with the susceptible control Enterococcus faecalis ATCC 29212. Further testing of two type B strains (E. faecalis V583 and V583-2) showed that certain other amino acids (i.e., D-methionine, D-serine, D-alanine, and D-phenylalanine) had effects similar to that of glycine. Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis with membrane preparations from these strains revealed the production of vancomycin-inducible proteins of sizes comparable to those describe for other enterococcal isolates that exhibit acquired vancomycin resistance. Even in the presence of 0.2 M glycine, the inducible proteins were produced. These results indicate that certain amino acids specifically interfere with the mechanism(s) of acquired vancomycin resistance in enterococci and that the nature of interference probably involves inhibition or circumvention of the inducible proteins' functions.
A Bacteroides tetracycline resistance gene represents a new class of ribosome protection tetracycline resistance
Authors: Nikolich M P , Shoemaker N B , Salyers A A
Published: June 2012

The ribosome protection type of tetracycline resistance (Tcr) has been found in a variety of bacterial species, but the only two classes described previously, Tet(M) and Tet(O), shared a high degree of amino acid sequence identity (greater than 75%). Thus, it appeared that this type of resistance emerged recently in evolution and spread among different species of bacteria by horizontal transmission. We obtained the DNA sequence of a Tcr gene from Bacteroides, a genus of gram-negative, obligately anaerobic bacteria that is phylogenetically distant from the diverse species in which tet(M) and tet(O) have been found. The Bacteroides Tcr gene defines a new class of ribosome protection resistance genes, Tet(Q), and has a deduced amino acid sequence that was only 40% identical to Tet(M) or Tet(O). Like tet(M) and tet(O), tet(Q) appears to have spread by horizontal transmission, but only within the Bacteroides group.
A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa
Authors: Piddock L J , Hall M C , Bellido F , Bains M , Hancock R E
Published: June 2012

An enoxacin-resistant Pseudomonas aeruginosa mutant (G49) isolated during patient therapy was characterized in detail. The G49 mutant was cross resistant to several classes of antibiotics including quinolones, beta-lactams, chloramphenicol, and tetracycline, but not imipenem or aminoglycosides. Compared with its paired pretherapy isolate G48, this mutant had several alterations in outer membrane proteins including a complete loss of the major porin protein OprF and a substantially altered lipopolysaccharide profile. Revertants were selected at a frequency of approximately 1% after enrichment for OprF+ cells on low-salt proteose peptone no. 2 medium. Ninety-seven of these OprF+ revertants were as susceptible to carbenicillin and norfloxacin as the pretherapy isolate. One of these revertants was characterized in more detail and shown to be indistinguishable in all properties from the pretherapy isolate. It is proposed that the multiple-antibiotic-resistance (Mar) phenotype of this mutant resulted from a single pleiotropic mutation.
Effect of pooled human cerebrospinal fluid on the postantibiotic effects of cefotaxime, ciprofloxacin, and gentamicin against Escherichia coli
Authors: Zhanel G G , Karlowsky J A , Davidson R J , Hoban D J
Published: June 2012

The killing and postantibiotic effects (PAE) of cefotaxime, ciprofloxacin, and gentamicin against Escherichia coli were determined in Mueller-Hinton broth (MHB) and pooled human cerebrospinal fluid (CSF). MICs performed in MHB and CSF were within one dilution for all antimicrobial agent-organism combinations. At two times the MIC, CSF significantly (P less than 0.05) increased the duration of the PAE compared with MHB when cefotaxime, ciprofloxacin, and gentamicin were used against all strains tested. This effect occurred despite similar reductions in bacterial growth in both fluids after the 2-h antimicrobial agent exposure. We conclude that pooled human CSF markedly increases the PAE of cefotaxime, ciprofloxacin, and gentamicin against E. coli compared with MHB, without affecting bacterial killing.
Inactivators of herpes simplex virus ribonucleotide reductase: hematological profiles and in vivo potentiation of the antiviral activity of acyclovir
Authors: Spector T , Lobe D C , Ellis M N , Blumenkopf T A , Szczech G M
Published: June 2012

A1110U (BW 1110U81) is an inactivator of herpesvirus ribonucleotide reductases and a potentiator of the antiviral activity of acyclovir (ACV) (T. Spector, J. A. Harrington, R. W. Morrison, Jr., C. U. Lambe, D. J. Nelson, D. R. Averett, K. Biron, and P. A. Furman, Proc. Natl. Acad. Sci. USA 86:1051-1055, 1989) that was subsequently found to cause hematological toxicity at high oral doses in rats. Eleven structurally related inactivators of herpes simplex virus (HSV) ribonucleotide reductase were therefore tested in vivo for hematological toxicity and for potentiation of ACV. None of the novel ribonucleotide reductase inactivators was hematologically toxic to rats following oral dosing at 60 mg/kg/day for 30 days. Four of these inactivators statistically improved the antiviral topical potency of ACV on HSV type 1-infected nude mice. A promising compound, 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl]thiocarbonohydrazone (BW 348U87), was studied more extensively in two in vivo models: dorsum-infected athymic nude mice and snout-infected hairless mice. BW 348U87 significantly potentiated the antiviral activity of ACV against all virus strains tested, i.e., wild-type (ACV-sensitive) HSV type 1 and HSV type 2 strains and three mutant (ACV-resistant) HSV type 1 strains. The latter included a virus expressing a DNA polymerase resistant to inhibition by ACV triphosphate, a virus deficient in thymidine kinase (the enzyme responsible for phosphorylating ACV), and a virus expressing an altered thymidine kinase, which catalyzes the normal phosphorylation of thymidine but not of ACV. BW 348U87 and ACV are currently being developed as a combination topical therapy for cutaneous herpes infections.
Excretion of cefprozil into human breast milk
Authors: Shyu W C , Shah V R , Campbell D A , Venitz J , Jaganathan V , Pittman K A , Wilber R B , Barbhaiya R H
Published: June 2012

The excretion of cefprozil into breast milk in nine healthy, lactating female subjects was investigated. Each subject received a single 1,000-mg oral dose of cefprozil consisting of cis and trans isomers in an approximately 90:10 ratio. Serial blood, urine, and breast milk samples were collected and analyzed for the concentrations of the cis and trans isomers by a specific high-pressure liquid chromatography-UV assay. The mean pharmacokinetic parameters for both isomers were essentially the same. The mean peak concentrations in plasma for the cis isomer were 14.8 micrograms/ml, and the area under the concentration curve was 54.8 micrograms.h/ml. The mean values of elimination half-life, renal clearance, and urinary excretion for the cis isomer were 1.69 h, 164 ml/min, and 60%, respectively. The mean concentrations in milk of the cis isomer over a 24-h period ranged from 0.25 to 3.36 micrograms/ml, with the maximum concentration appearing at 6 h after dosing. The average maximum concentration in milk of the trans isomer was less than 0.26 micrograms/ml. The concentrations of the trans isomer in plasma and in breast milk were about 1/10 of those for the cis isomer. Less than 0.3% of the dose was excreted in breast milk for both isomers of cefprozil. Even if one assumes that the concentration of cefprozil in milk remains constant at 3.36 micrograms/ml (the highest concentration of cefprozil observed in breast milk), an infant ingesting an average of 800 ml of milk per day will be exposed to a maximum amount of about 3 mg of cefprozil per day. This value represents about 0.3% of the maternal dose. Low excretion of cefprozil in breast milk and the excellent safety profile of cefprozil suggest that this cephalosporin may be administered to nursing mothers when indicated.
Dissociation of the antimicrobial activity of bacitracin USP from its renovascular effects
Authors: Drapeau G , Petitclerc E , Toulouse A , Marceau F
Published: June 2012

Bacitracin is a nephrotoxic antibiotic that has recently been shown to induce contractile effects in aortas isolated from rabbits by stimulating receptors for 5-hydroxytryptamine (5-HT). The possible renovascular actions of this antibiotic were investigated. Bacitracin USP increased the vascular resistance in a concentration-dependent manner (9 to 175 micrograms/ml) in rat kidneys perfused with a constant flow of Krebs solution. This was significantly inhibited by 5-HT antagonists, but only partially at the higher bacitracin concentration. An antagonist of the chemotactic peptide fMet-Leu-Phe failed to influence the pressor effect of bacitracin in rat kidneys. Indomethacin modestly reduced the effect of all potent pressor agents in the rat organ. Bacitracin USP was separated in several fractions by using C18 reverse-phase chromatography. Two distinct fractions were vasoconstrictive when infused in rat kidneys; both fractions were 5-HT mimetics. These peaks were different from the major antibiotic peak, bacitracin A, which was identified by using analytical high-pressure liquid chromatography, mass spectrometry, and inhibition of Micrococcus luteus growth. The less polar vasoactive peak corresponded to at least two minor peptides of the bacitracin family. The most abundant of these vasoactive peptides had no direct contractile effect on an aorta isolated from a rabbit, but a preliminary metabolic study in rat kidneys suggests that it is apparently transformed into a potent 5-HT agonist that is active on the aorta preparation. Bacitracin A, the major constituent of bacitracin with antimicrobial activity, had no vasoconstrictor effect in the test systems that we used; however, we did rule out the possibility that the renovascular stimulants found in the bacitracin mixture do not derive spontaneously or by biotransformation from the antibacterial forms of bacitracin.
Effect of antacid on the bioavailability of cefprozil
Authors: Shyu W C , Wilber R B , Pittman K A , Barbhaiya R H
Published: June 2012

The effect of antacid on the bioavailability of cefprozil was investigated in a two-way crossover study. Eight healthy male subjects received a single 500-mg oral dose of cefprozil with and without coadministration of 30 ml of an antacid suspension containing magnesium hydroxide and aluminum hydroxide (Maalox). Cefprozil consists of cis and trans isomers in an approximate 90:10 ratio. When cefprozil was administered alone (treatment A), the mean maximum concentrations (Cmax) of the cis and trans isomers were 9.2 and 1.2 micrograms/ml, respectively. When cefprozil was coadministered with Maalox (treatment B), the Cmax values of the cis and trans isomers were 8.7 and 1.3 micrograms/ml, respectively. The mean values of the area under the curve from time zero to infinity (AUC0-infinity) were 27.7 and 3.5 micrograms.h/ml for treatment A and 27.5 and 3.5 micrograms.h/ml for treatment B for the cis and trans isomers, respectively. The other pharmacokinetic parameters, time to Cmax, elimination half-life, mean residence time, renal clearance, and percent urinary excretion, were essentially the same for the two isomers. The respective values of the elimination half-life for the cis and trans isomers were 1.36 and 1.32 h for treatment A and 1.36 and 1.42 h for treatment B. Mean urinary excretion was 63 and 60% for treatment A and 58 and 56% for treatment B for the cis and trans isomers, respectively. No significant differences between the two treatments were found for any of the pharmacokinetic parameters for either isomer. For the cis isomer, bioavailability point estimates (90% confidence intervals) of the mean Cmax and AUG0-infinity values for the Maalox treatment relative to those for the reference treatment were 95% (87%, 103%) and 99% (95%, 104%), respectively. For the trans isomer, the value were 109% (92%, 126%) for Cmax and 97% (88%, 106%) for AUC0-infinity. On the basis of the results of this study, it is concluded that the bioavailability of cefprozil is not affected by the coadministration of Maalox.
Impact of bioavailability on determination of the maximal tolerated dose of 2',3'-dideoxyinosine in phase I trials
Authors: Drusano G L , Yuen G J , Morse G , Cooley T P , Seidlin M , Lambert J S , Liebman H A , Valentine F T , Dolin R
Published: June 2012

The objective of this study was to determine the population pharmacokinetic parameters and the extent of absorption of 2',3'-dideoxyinosine, a nucleoside analog with activity against human immunodeficiency virus in vitro and in vivo, after oral and intravenous administration through the use of NON-linear Mixed Effects Modeling. The data were drawn from the pharmacokinetics section of an open-label, multicenter phase I study. One center administered ddI on a once-daily schedule. The other centers administered the drug once every 12 h. Drug was administered intravenously, and the plasma concentration-time profile was determined. Patients were then given the drug orally at twice the dose used in the intravenous portion of the study, and the pharmacokinetic profile was again determined. A 40-fold range of doses was examined. Forty-six human immunodeficiency virus-infected patients were studied. Concentrations in plasma were determined by high-pressure liquid chromatography. Clearance of the drug from plasma was 47.7 liters/h/70 kg of body weight. The terminal half-life was 1.4 h. The volume of distribution in the central compartment was 18.8 liters/70 kg. Absorption was rapid, with an absorption half-life of 0.52 h. Bioavailability with once-daily administration was 27%. For twice-daily administration, bioavailability rose to 36%. This difference was significant (P much less than 0.01). For doses of less than or equal to 5.1 mg/kg given every 12 h (10.2 mg/kg/day), bioavailability was 41%. We conclude that once-daily administration results in lower mean bioavailability, probably because of a saturation of the absorption process similar to that seen with acyclovir. This difference in bioavailability on the basis of the administration schedule explains the different short-term maximal tolerated doses identified in phase I trials of this agent.
Effects of a human antiflagellar monoclonal antibody in combination with antibiotics on Pseudomonas aeruginosa infection
Authors: Uezumi I , Terashima M , Kohzuki T , Kato M , Irie K , Ochi H , Noguchi H
Published: June 2012

The in vivo activity of human immunoglobulin M monoclonal antibody IN-2A8, which is specific for flagellum type b of Pseudomonas aeruginosa, was evaluated in comparison to anti-O antigen (serotype B) MAb KO-2F2 and in combination with antibiotics. IN-2A8 showed stronger activity than KO-2F2 against subcutaneous infection in burned mice, while it was much less active against intraperitoneal infection in normal mice. In a burn infection model, IN-2A8 inhibited the increase of bacteria in skin lesions weakly and that in blood significantly, suggesting that it strongly suppressed bacterial spread to blood. The activity of IN-2A8 in combination with 10 antipseudomonal antibiotics against intraperitoneal infection was examined. Clear additive effect was observed with a combination of either carbapenem or aminoglycoside antibiotics in terms of mouse survival. The administration of an antibiotic, imipenem-cilastatin, simultaneously with or before that of IN-2A8 gave a combined effect, but the reverse order did not. The combination of IN-2A8 with imipenem-cilastatin decreased numbers of viable bacteria in the peritoneal cavity and blood and kept them low for a longer time than did either treatment alone. These results suggest that an antiflagellar monoclonal antibody would be effective against systemic infection in combination with some kinds of antibiotics.
Antimicrobial susceptibilities of a Corynebacterium CDC group I1 strain isolated from a patient with endocarditis
Authors: Malanoski G J , Parker R , Eliopoulos G M
Published: June 2012

We encountered a case of native valve endocarditis due to Corynebacterium CDC group I1 which was successfully controlled with antimicrobial agents alone. This organism and three other isolates of this group were susceptible to penicillin, vancomycin, and gentamicin. The combination of penicillin with subinhibitory concentrations of gentamicin resulted in a 1,000-fold decrease in CFU per milliliter at 24 h compared with penicillin alone. Augmentation of killing was noted also with vancomycin plus gentamicin but to a degree that did not meet strict criteria for bactericidal synergism.
In vitro activity and beta-lactamase stability of LJC 10,627
Authors: Neu H C , Gu J W , Fang W , Chin N X
Published: June 2012

The in vitro activity of LJC 10,627, a new carbapenem, was compared with those of imipenem, cefotaxime, ceftazidime, and gentamicin. LJC 10,627 inhibited 90% of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Enterobacter agglomerans, Enterobacter cloacae, Hafnia alvei, Citrobacter freundii, Citrobacter diversus, Proteus mirabilis, Morganella morganii, Proteus rettgeri, Serratia marcescens, Pseudomonas cepacia, salmonellae, shigellae, aeromonas, and yersiniae at less than or equal to 2 micrograms/ml. Haemophilus influenzae was inhibited by 0.5 microgram/ml, and moraxellae were inhibited by 0.12 microgram/ml. LJC 10,627 was twofold more active than imipenem against aerobic gram-negative organisms and inhibited ceftazidime-, cefotaxime-, and gentamicin-resistant members of the genera Klebsiella, Enterobacter, Citrobacter, and Serratia at less than or equal to 2 micrograms/ml. Xanthomonas maltophilia strains were resistant to the drug. Imipenem was two- to fourfold more active than LJC 10,627 against Staphylococcus aureus and Staphylococcus epidermidis. LJC 10,627 did not inhibit most methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis strains. LJC 10,627 inhibited Streptococcus pyogenes and Streptococcus pneumoniae at 0.06 and 0.12 microgram/ml, respectively. Bacteroides fragilis and other Bacteroides spp. were inhibited by 0.5 microgram of LJC 10,627 per ml. Serum (50%) did not affect the MICs. LJC 10,627 was not hydrolyzed by plasmid-mediated beta-lactamases of Bush types 2b, 2b', TEM-1, TEM-2, TEM-3, TEM-5, TEM-7, TEM-9, and SHV-1; the chromosomal beta-lactamases of Bush type 1; P-99; a Morganella enzyme; or a Citrobacter freundii enzyme. The Bush type 2c and 2d enzymes OXA-1, OXA-2, PSE-1, PSE-2, and PSE-4 did not hydrolyze LJC 10,627, nor did the beta-lactamases of Staphylococcus aureus, Moraxella spp., Bacteroides fragilis, and Proteus vulgaris. The beta-lactamase of Xanthomonas hydrolyzed LJC 10,627, albeit at approximately one-third the rate that imipenem was hydrolyzed.
Simulation of human serum pharmacokinetics of cefazolin, piperacillin, and BRL 42715 in rats and efficacy against experimental intraperitoneal infections
Authors: Woodnutt G , Berry V , Mizen L
Published: June 2012

Studies were performed to determine the effects of BRL 42715, a potent beta-lactamase inhibitor, on the activity of cefazolin and piperacillin against experimental intraperitoneal infections caused by either Escherichia coli or Serratia marcescens in rats. Compounds were administered to rats as a continuous infusion of an exponentially diluted solution to simulate in rat plasma the concentration-versus-time curves obtained for humans following intravenous bolus administration. A simulated 1-g dose of cefazolin was ineffective in reducing the bacterial counts in blood and peritoneal fluid samples of animals infected with S. marcescens US20, which produced class Ia beta-lactamase, and as a result, mortality was similar to that of infected controls. Similarly, a simulated 2-g dose of piperacillin was ineffective in reducing bacterial numbers and mortality in animals infected with E. coli 41548, producing a TEM-1 beta-lactamase. However, when the antibiotics were coadministered with BRL 42715, bacterial numbers were reduced significantly and all animals survived at least 16 h after infection. These data demonstrate the ability of BRL 42715 to potentiate the activity of cefazolin and piperacillin against beta-lactamase-producing bacteria that would otherwise be resistant to these antibiotics and illustrate the application of a model to simulate human serum concentrations in conscious rats.