bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacodynamics of piperacillin alone and in combination with tazobactam against piperacillin-resistant and -susceptible organisms in an in vitro model of infection
Authors: Strayer A H , Gilbert D H , Pivarnik P , Medeiros A A , Zinner S H , Dudley M N
Published: June 2012

The pharmacodynamics of dosage regimens of piperacillin alone or in combination with tazobactam against piperacillin-resistant or -susceptible bacteria were studied in an in vitro model of infection. Experiments were conducted by using a fixed daily exposure of 12 g of piperacillin, given as 3 g alone or in combination with tazobactam at 0.375 g every 6 h, or the same total dose of the combination given as 4 g of piperacillin plus 0.5 g of tazobactam every 8 h. The addition of tazobactam to piperacillin, irrespective of the dosing interval, did not alter the killing of piperacillin-susceptible organisms (Escherichia coli J53 and Pseudomonas aeruginosa ATCC 27853). In contrast, experiments with an isogenic TEM-3-containing transconjugant of E. coli J53 (E. coli J53.2-TEM-3) that was resistant to piperacillin (MIC, 128 micrograms/ml) showed that the addition of tazobactam resulted in bacterial killing similar to that observed with the wild-type strain. Although tazobactam concentrations fell to less than 4 mg/liter (the concentration associated with a reduction in the piperacillin MIC from 128 to 2 mg/liter) 2 to 3 h after a dose, a similar degree of bacterial killing was observed when the same total 24-h dose of piperacillin-tazobactam was fractionated into dosing intervals of every 6 or 8 h. Investigations with Staphylococcus aureus 7176 (piperacillin MIC, 128 micrograms/ml) showed that the addition of tazobactam, again irrespective of dosing interval, also resulted in net bacterial killing which was not seen with piperacillin alone. These data support the use of extended dosing intervals (every 8 h) of piperacillin-tazobactam in the treatment of infections caused by piperacillin-resistant bacteria.
Standardization of disk diffusion test and its clinical significance for susceptibility testing of metronidazole against Helicobacter pylori
Authors: Xia H , Keane C T , Beattie S , O'Morain C A
Published: June 2012

Susceptibilities of 121 clinical Helicobacter pylori strains to metronidazole were determined by both a 5-micrograms metronidazole disk diffusion test and a plate dilution method in duplicate and after different periods of incubation. The distribution of MICs of metronidazole against H. pylori among the strains was found to be bimodal. The diameters of inhibitory zones obtained by the disk diffusion test and the MICs obtained by the plate dilution method correlated well, especially after 4 days of incubation (r = 0.77). An inhibitory zone diameter of 20 mm was found to correspond to a MIC of 8 micrograms/ml and is recommended as a suitable zone for differentiating susceptibility and resistance with a 5-micrograms metronidazole disk. Three interpretive categories of susceptibility results were defined; strains with inhibitory zone diameters of more than 26 mm were defined as susceptible (MIC, < 4 micrograms/ml), strains with zone diameters of 20 to 26 mm were deemed intermediate (MIC, 4 to 8 micrograms/ml), and those with zone diameters of less than 20 mm were deemed resistant (MIC, > 8 micrograms/ml). Furthermore, 76 H. pylori-positive patients with duodenal ulcers or nonulcer dyspepsia were treated with a 1 week of triple therapy (colloidal bismuth subcitrate, metronidazole, and tetracycline). H. pylori strains were isolated before treatment from antral biopsies from those patients, and the metronidazole susceptibilities of the strains were determined by the disk diffusion test. H. pylori status was evaluated again 4 weeks after completion of treatment. The eradication rates for susceptible, intermediate, and resistant strains were 95.9% (47 of 49), 62.5% (5 of 8), and 52.6% (10 of 19), respectively. It is included that the 5-micrograms disk diffusion test is easy to perform and gives final results similar to those of the plate dilution method. The three interpretive categories of susceptibility may be of benefit for clinical choice of chemotherapy in eradicating H. pylori.
The endocytic process in CHO cells, a toxic pathway of the polyene antibiotic amphotericin B
Authors: Vertut-Doï A , Ohnishi S I , Bolard J
Published: June 2012

We describe the fate of the polyene antibiotic amphotericin B (AmB) after its interaction with Chinese hamster ovary (CHO) cells. The global uptake of AmB by these cells was measured at 37 degrees C after a 1-h incubation in the presence of 5% fetal bovine serum. It increased with the total concentration of drug and reached a plateau of approximately 1 nmol/mg of cell protein for an external concentration of 25 microM. The same experiment performed at 5 degrees C revealed a drastic decrease in uptake. The distribution of the drug among plasma membranes, endosomes, and lysosomes was then investigated after the separation of the postnuclear fractions by a Percoll gradient. After a 10-min incubation, AmB was found only in the plasma membrane fraction, regardless of the drug concentrations used (5 to 100 microM). After 60 min, at low drug concentrations (5 and 10 microM) AmB was found to be incorporated mainly in plasma and lysosomal fractions. At high concentrations (50 microM) AmB accumulated in endosomal fractions and plasma membranes. At intermediate concentrations (25 microM) AmB was distributed among the three fractions. When the same experiment was carried out at 5 degrees C, AmB was associated only with the plasma membrane even after 60 min, which was consistent with the absence of endocytotic process at low temperature. The effect of AmB on the endocytic process resulted in the increased uptake of sulforhodamine B, a fluid-phase marker of endocytosis, as well as by the accumulation of sulforhodamine in spots scattered in the cytoplasms of AmB-treated cells, in contrast to the accumulation around the nuclei observed in the control cells. These results are interpreted as indicating that AmB is internalized by the cells through endocytosis and that high concentrations of the drug block the fusion between endosomes and/or the fusion between endosomes and lysosomes.
Comparison of rates of intracellular metabolism of zidovudine in human and primate peripheral blood mononuclear cells
Authors: Qian M , Chandrasena G , Ho R J , Unadkat J D
Published: June 2012

3'-Azido-3'-deoxythymidine (AZT) is a drug of choice for the treatment of AIDS. On the basis of pharmacokinetic data, the nonhuman primate Macaca nemestrina has been shown to be a suitable animal model for use in the study of the disposition of AZT. However, since AZT is activated to its metabolite, the AZT triphosphate (AZTTP), intracellularly, we investigated the intracellular activation of AZT in peripheral blood mononuclear cells (PBMCs) of healthy and simian immunodeficiency virus-infected macaques and compared it with that in PBMCs obtained from human volunteers. At 5 microM extracellular AZT, both human and macaque PBMCs rapidly convert AZT to AZT monophosphate (AZTMP) (84% of total phosphorylated products) in 4 h. Increases in AZTMP levels of 7.7- and 12-fold were observed in human and macaque PBMCs, respectively, when the extracellular AZT concentration increased from 0.45 to 14.4 microM. Similar ratios of AZT metabolites, AZT diphosphate (AZTDP)/AZTTP (0.7 to 1.4), AZTMP/AZTDP (3 to 14), and AZTMP/AZTTP (3 to 19), over the same AZT concentration range were observed in both human and macaque PBMCs, suggesting that these cells have similar capacities to phosphorylate AZT. Simian immunodeficiency virus-infected macaque PBMCs showed a fivefold increase in intracellular AZT and AZTMP levels and a twofold increase in AZTDP and AZTTP levels (picomoles per 10(7) cells) when compared with those in the uninfected cells (at 4 h with 0.9 microM extracellular concentration). This increase in AZT metabolite levels has also been reported for human immunodeficiency virus-infected PBMCs. Collectively, given the similarities in phosphorylation profiles between healthy and infected human and macaque PBMCs, we conclude that the macaque is a suitable animal model for use in the study of factors that can effect the in vivo phosphorylation of AZT.
Biocidal action of chlorhexidine is annulled by nicotinic acid
Authors: Baker H , Frank O , DeAngelis B , Baker E R
Published: June 2012

An analytical system comprising a bacterium and a protozoan was used to pinpoint the metabolic lesion whereby chlorhexidine (CLX) produced cell death. Nicotinic acid but not nicotinamide annulled the biocidal action of CLX. The results suggest that CLX may not permit bioconversion of nicotinamide to nicotinic acid to annul the growth inhibition induced by CLX.
Anti-human immunodeficiency virus type 1 activities of U-90152 and U-75875 in human brain cell cultures
Authors: Peterson P K , Gekker G , Hu S , Chao C C
Published: June 2012

Antiviral activities of the reverse transcriptase inhibitors U-90152 and 3'-azido-2',3'-dideoxythymidine and the protease inhibitor U-75875 were compared in two culture models of human immunodeficiency virus type 1 brain infection. In a model involving acutely infected microglial cells, U-90152 was the most active, whereas in a model using chronically infected promonocytes, U-75875 was the most active.
Detection of 4-quinolone resistance mutation in gyrA gene of Shigella dysenteriae type 1 by PCR
Authors: Rahman M , Mauff G , Levy J , Couturier M , Pulverer G , Glasdorff N , Butzler J P
Published: June 2012

To study 4-quinolone resistance, the N-terminal coding region of gyrA from nalidixic acid-susceptible and -resistant isolates of Shigella dysenteriae type 1 was amplified by PCR, cloned, and sequenced. DNA sequence analysis of gyrA from nalidixic acid-resistant isolates revealed a C-to-T transition at nucleotide position 248 leading to a Ser-83-to-Leu substitution which was absent in susceptible clinical isolates. Direct HinfI digestion of PCR-amplified DNA detected similar mutations. Thus, DNA gyrase A subunit mutation Ser-83 to Leu is implicated in 4-quinolone resistance in S. dysenteriae type 1.
Ability of cecropin B to penetrate the enterobacterial outer membrane
Authors: Vaara M , Vaara T
Published: June 2012

The cationic amphipathic insect peptide cecropin B was almost as active on wild-type enteric bacteria as it was on their lipopolysaccharide and lipid A mutants that have very defective outer membrane. The polymyxin-resistant strains, which elaborate altered, less anionic lipopolysaccharide, were completely susceptible to cecropin B. No synergism was found between cecropin B and hydrophobic antibiotics. Throughout the study, the activity of cecropin B resembled that of quaternary detergents.
In vitro activities of two new glycylcyclines, N,N-dimethylglycylamido derivatives of minocycline and 6-demethyl-6-deoxytetracycline, against 339 strains of anaerobic bacteria
Authors: Wexler H M , Molitoris E , Finegold S M
Published: June 2012

The in vitro activities of the N,N-dimethylglycylamido derivatives of minocycline (DMG-MINO) and 6-demethyl-6-deoxytetracycline (DMG-DMDOT) were compared with those of minocycline, tetracycline, clindamycin, and metronidazole by using the National Committee for Clinical Laboratory Standards-approved Wadsworth agar dilution method. The MICs of DMG-MINO, DMG-DMDOT, and metronidazole at which 90% of the strains were susceptible (0.5, 1, and 1 micrograms/ml, respectively) were lower than those for clindamycin, minocycline, and tetracycline (4, 8, and 32 micrograms/ml, respectively). All of the strains of anaerobes tested, except one strain of Bacteroides ovatus (MIC, 16 micrograms/ml), were susceptible to DMG-MINO and DMG-DMDOT at 8 micrograms/ml.
Comparative efficacies of amphotericin B, triazoles, and combination of both as experimental therapy for murine trichosporonosis
Authors: Anaissie E J , Hachem R , Karyotakis N C , Gokaslan A , Dignani M C , Stephens L C , Tin-U C K
Published: June 2012

We assessed the activities of amphotericin B deoxycholate, liposomal amphotericin B, fluconazole, and SCH 39304 against 10 strains of Trichosporon beigelii in mice with hematogenous infections. Cyclophosphamide-immunosuppressed CF1 male mice were challenged intravenously with a lethal inoculum of T. beigelii (5 x 10(6) conidia per mouse) and were assigned to different treatment groups or were left untreated. Amphotericin B deoxycholate (1 mg/kg of body weight and liposomal amphotericin B (1, 5, and 10 mg/kg) were given parenterally once daily. Escalating doses (5, 10, and 20 mg/kg/day) of fluconazole and SCH 39304 were tested. We also compared the activity of amphotericin B deoxycholate plus fluconazole (1 and 10 mg/kg/day, respectively) with that of each agent alone. Fluconazole significantly prolonged the survival of mice infected with each of the 10 strains tested. Amphotericin B deoxycholate achieved various responses, improving the outcomes in mice infected with seven of the strains. Liposomal amphotericin B was not more effective than amphotericin B deoxycholate against the two strains tested. Both fluconazole and SCH 39304 reduced the kidney fungal counts in a dose-dependent pattern, with SCH 39304 being more active than fluconazole against one of the two strains tested. The activity of the combination of amphotericin B deoxycholate plus fluconazole appeared to be superior to that of either agent alone, especially in reducing the kidney fungal burden. Fluconazole is more active than amphotericin B deoxycholate against experimental murine trichosporonosis.
Ornithine decarboxylase in Pneumocystis carinii and implications for therapy
Authors: Sarić M , Clarkson A B
Published: June 2012

Pneumocystis carinii pneumonia (PCP) can be treated with eflornithine (difluoromethylornithine, DFMO, Ornidyl), a competitive irreversible inhibitor of ornithine decarboxylase (ODC), a key enzyme for polyamine biosynthesis. Because ODC has been reported to be absent from P. carinii, it has been assumed that eflornithine affects P. carinii only indirectly, by affecting host polyamine biosynthesis. If this is true, then improvements in the selectivity of antipolyamine therapy for PCP would be limited. Since the presence of ODC in P. carinii is an important issue, a new search for this enzyme was made. Not only were initial assays negative, but P. carinii extract reduced the background catalytic action of pyridoxal-5'-phosphate, the coenzyme required by the enzyme. This suggested the presence of an inhibitor, which was further supported by the observation that a P. carinii extract could suppress a source of known ODC activity. The inhibitory activity could be removed by a desalting column or by dialysis, allowing detection of P. carinii ODC. Indirect evidence indicates that the inhibition is only apparent and is caused by unlabeled ornithine in the extract of P. carinii which interferes with the radiolabel-based assay system. P. carinii and host ODCs respond differently to changes in pH. P. carinii ODC is much less susceptible to inhibition by eflornithine than host ODC. The presence of ODC in P. carinii suggests that P. carinii ODC is the target of eflornithine and that P. carinii ODC may have sufficiently specific properties that inhibitors with improved selectivity against P. carinii ODC could be identified.
Inhibition of antibacterial activity of himastatin, a new antitumor antibiotic from Streptomyces hygroscopicus, by fatty acid sodium salts
Authors: Mamber S W , Brookshire K W , Dean B J , Firestone R A , Leet J E , Matson J A , Forenza S
Published: June 2012

Himastatin, a cyclohexadepsipeptide antibiotic, had in vivo antitumor activity against localized P388 leukemia and B16 melanoma but had no distal site antitumor activity. An in vitro Bacillus subtilis well-agar diffusion assay was employed to test the hypothesis that himastatin was enzymatically inactivated. The activity of himastatin against B. subtilis was inhibited when himastatin was mixed with mouse liver S9 fraction and microsomes. However, subsequent investigations demonstrated that the markedly decreased antibacterial activity was not enzymatic in nature but was related to the presence of certain fatty acid salts. Saturated fatty acid sodium salts with a carbon chain number of 8 or more reduced the antimicrobial activity of himastatin 50 to 100 times. If antibiotics such as ampicillin, bacitracin, chloramphenicol, and tunicamycin were used in place of himastatin, no meaningful reduction in antibacterial activity occurred. However, the antibacterial activity of the membrane-active peptide antibiotic polymyxin B, but not that of polymyxin E (colistin), was reduced in a manner similar to that of himastatin. Importantly, the activity of himastatin against HCT-116 colon adenocarcinoma cells in soft agar was markedly reduced in the presence of sodium palmitate as the reference fatty acid salt. The data indicate that himastatin may be trapped in micelles in vitro. It may be speculated that the lack of distal site antitumor activity resulted from similar complex formation between himastatin and lipids in vivo. The results also suggest that the cancer cytotoxic and antimicrobial effects of himastatin may result from interactions with the cell membrane.
Growth of Cryptococcus neoformans in presence of L-dopa decreases its susceptibility to amphotericin B
Authors: Wang Y , Casadevall A
Published: June 2012

Cryptococcus neoformans grown with L-dopa was melanized and was less susceptible to amphotericin B. The results suggest that in vivo and in vitro susceptibilities to amphotericin B may differ.
Evidence of alkaline phosphatase interference in a zidovudine radioimmunoassay
Authors: O'Donnell A M , Letting D J , DeRemer M F , Morse G D
Published: June 2012

Phosphorylated zidovudine (ZDV) concentrations may provide a link between drug exposure and clinical efficacy since these would include the active, intracellular form of the drug, ZDV triphosphate. Many groups are investigating the optimal methodology that can be used to accomplish this goal. The initial purpose of the present studies was to examine the effect of the inclusion of cell wash steps on the quantitation of intracellular ZDV. Ten milliliters of whole blood collected from healthy volunteers was spiked with increasing ZDV concentrations (0.187, 0.375, 1.87, and 3.75 microM), allowed to equilibrate at room temperature for 1 h, and separated into whole-blood components by a density gradient procedure. A mononuclear cell pellet was obtained, reconstituted with 2 ml of phosphate-buffered saline (PBS), and split into two aliquots, one of which was not washed at all and the other of which was washed four times with 1 ml of PBS. All samples were analyzed by ZDV radioimmunoassay (RIA) after a 1:1 dilution with either 1 mg of alkaline phosphatase (type 1-S; Sigma) per ml or PBS. Parent ZDV was measured in those samples which were not treated with the enzyme, while total ZDV was measured in those samples which were exposed to alkaline phosphatase (21 degrees C for 1 h). The result of the difference between the two samples is total phosphorylated ZDV. During the experiment, evidence of alkaline phosphatase interference with the RIA became apparent, confusing interpretation of intracellular ZDV concentrations. This evidence was based on three sets of data. First, wash samples showed increases in ZDV concentrations of as great as 0.127 microgramM after exposure to alkaline phosphatase, even though on microscopic inspection the wash samples were acellular. Second, the sum of total ZDV recovered from the four wash samples plus the washed cell pellet was as much as 14-fold greater than the total ZDV measured in the unwashed cell pellet. Theoretically, at least, these two entities should be equal. Finally, control samples of alkaline phosphatase in PBS (0.5 mg/ml) run directly through the assay measured false ZDV levels ranging from 0.002 to 0.075 microgramM (0.6 to 20 ng/ml). Alkaline phosphatase is frequently used to measure phosphorylated anabolites of ZDV in peripheral blood mononuclear cells. These data show that the particular form of alkaline phosphatase used may interfere with the ZDV RIA and may confuse the interpretation of phosphorylated anabolite concentrations of ZDV.
Pharmacokinetics, toxicity, and efficacy of liposomal capreomycin in disseminated Mycobacterium avium beige mouse model
Authors: Le Conte P , Le Gallou F , Potel G , Struillou L , Baron D , Drugeon H B
Published: June 2012

Capreomycin was incorporated into multilamellar vesicles of pure dipalmitoylphosphatidylcholine. The pharmacokinetics and nephrotoxicity of capreomycin in the free and liposomal forms were studied in normal mice. The efficacies of the two forms were evaluated by using the Mycobacterium avium complex beige mouse model. Approximately 10(7) viable M. avium cells were injected intravenously. Seven days later, treatment with either liposomal or free capreomycin at 60 or 120 mg/kg of body weight was administered daily for 5 days. Mice were sacrificed 5 days after the end of treatment, and the viable bacteria in liver, spleen, lungs, and blood were counted. After 5 days of treatment with dosages of 60 or 120 mg/kg/day, the level of blood urea nitrogen increased in the group treated with free capreomycin but not in the group treated with liposomal capreomycin. After intravenous injection of 120 mg/kg, liposomes enhanced the diffusion of capreomycin in the spleen, lungs, and kidneys and increased the half-life in serum. The 120-mg/kg dose of liposomal capreomycin significantly reduced the number of viable mycobacteria in the liver, spleen, and blood compared with those in the controls. Although these results are promising, further studies are needed to assess the efficacy of liposomal capreomycin for the treatment of M. avium complex infections.
Effects of antiviral nucleoside analogs on human DNA polymerases and mitochondrial DNA synthesis
Authors: Martin J L , Brown C E , Matthews-Davis N , Reardon J E
Published: June 2012

Inhibition constants were determined for 16 nucleoside analog triphosphates against human DNA polymerases alpha, beta, gamma, and epsilon, and 7 nucleoside analogs were examined as inhibitors of mitochondrial DNA synthesis in human Molt-4 cells in culture. The results demonstrate no clear quantitative or qualitative correlation between inhibition of DNA polymerases, particularly mitochondrial DNA polymerase gamma, and the inhibition of mitochondrial DNA synthesis in Molt-4 cell culture. Furthermore, the data indicate that inhibition of isolated DNA polymerases may not be predictive of in vitro or in vivo toxicity. Finally, it is not clear whether inhibition of mitochondrial DNA synthesis will be an accurate predictor of the potential in vivo toxicity of antiviral nucleoside analogs.
Intranasal monoclonal immunoglobulin A against respiratory syncytial virus protects against upper and lower respiratory tract infections in mice
Authors: Weltzin R , Hsu S A , Mittler E S , Georgakopoulos K , Monath T P
Published: June 2012

The role of secretory antibody in protection against respiratory syncytial virus (RSV) infection was examined by using monoclonal immunoglobulin A (IgA) antibody for intranasal passive immunization of mice. Eight anti-RSV IgA hybridomas were produced by fusing myeloma cells with lung lymphocytes from RSV-immunized mice. Five IgA antibodies recognized RSV strains of both the A and the B subgroups, and two of these neutralized virus in a plaque reduction assay. Monoclonal IgA antibody HNK20, which bound to F glycoprotein, was most effective, reducing plaques by 50% at a concentration of 0.1 microgram/ml for both subgroup A and subgroup B strains. HNK20 also neutralized all of eight clinical isolates of RSV tested. When delivered intranasally to mice 24 h prior to RSV challenge, HNK20 reduced virus titers in the lungs by nearly 100-fold. Maximal protection occurred at a dose of 0.5 mg/kg of body weight. Significant protection against lung infection was seen when the interval between antibody treatment and challenge was as long as 72 h. HNK20 also decreased virus titers in the nose approximately 10-fold when given 1 h, but not 24 h, before challenge. When mice were treated with HNK20 intranasally 3 days after challenge, viral titers were reduced in the lungs but not the nose. The results indicate that topical application of relatively small amounts of monoclonal IgA can protect against both upper and lower respiratory tract infections caused by RSV.
Inhibition of cap (m7GpppXm)-dependent endonuclease of influenza virus by 4-substituted 2,4-dioxobutanoic acid compounds
Authors: Tomassini J , Selnick H , Davies M E , Armstrong M E , Baldwin J , Bourgeois M , Hastings J , Hazuda D , Lewis J , McClements W
Published: June 2012

Synthesis of influenza virus mRNA is primed by capped and methylated (cap 1, m7GpppXm) RNAs which the virus derives by endonucleolytic cleavage from RNA polymerase II transcripts in host cells. The conserved nature of the endonucleolytic processing provides a unique target for the development of antiviral agents for influenza viruses. A series of 4-substituted 2,4-dioxobutanoic acid compounds has been identified as selective inhibitors of this activity in both influenza A and B viruses. These inhibitors exhibited 50% inhibitory concentrations in the range of 0.2 to 29.0 microM for cap-dependent influenza virus transcription and had no effect on the activity of other viral and cellular polymerases when tested at 100- to 500-fold higher concentrations. The compounds did not inhibit the initiation or elongation of influenza virus mRNA synthesis but specifically inhibited the cleavage of capped RNAs by the influenza virus endonuclease and were not inhibitory to the activities of other nucleases. Additionally, the compounds specifically inhibited replication of influenza A and B viruses in cell culture with potencies comparable to the 50% inhibitory concentrations obtained for transcription.
Simulation of amoxicillin pharmacokinetics in humans for the prevention of streptococcal endocarditis in rats
Authors: Fluckiger U , Moreillon P , Blaser J , Bickle M , Glauser M P , Francioli P
Published: June 2012

The pharmacokinetic determinants of successful antibiotic prophylaxis of endocarditis are not precisely known. Differences in half-lives of antibiotics between animals and humans preclude extrapolation of animal results to human situations. To overcome this limitation, we have mimicked in rats the amoxicillin kinetics in humans following a 3-g oral dose (as often used for prophylaxis of endocarditis) by delivering the drug through a computerized pump. Rats with catheter-induced vegetations were challenged with either of two strains of antibiotic-tolerant viridans group streptococci. Antibiotics were given either through the pump (to simulate the whole kinetic profile during prophylaxis in humans) or as an intravenous bolus which imitated only the peak level of amoxicillin (18 mg/liter) in human serum. Prophylaxis by intravenous bolus was inoculum dependent and afforded a limited protection only in rats challenged with the minimum inoculum size infecting > or = 90% of untreated controls. In contrast, simulation of kinetics in humans significantly protected animals challenged with 10 to 100 times the inoculum of either of the test organisms infecting > or = 90% of untreated controls. Thus, simulation of the profiles of amoxicillin prophylaxis in human serum was more efficacious than mere imitation of the transient peak level in rats. This confirms previous studies suggesting that the duration for which the serum amoxicillin level remained detectable (not only the magnitude of the peak) was an important parameter in successful prophylaxis of endocarditis. The results also suggest that single-dose prophylaxis with 3 g of amoxicillin in humans might be more effective than predicted by conventional animal models in which only peak levels of antibiotic in human serum were stimulated.
New in vitro assay based on glucose consumption for determining intraconazole and amphotericin B activities against Aspergillus fumigatus
Authors: Garrigues J C , Cadet de Fontenay G , Linas M D , Lagente M , Seguela J P
Published: June 2012

We developed a new in vitro method of evaluating antifungal molecules. Fungal growth was determined by measuring glucose consumption, the only carbon source in a synthetic medium. First, the growth of 12 Aspergillus fumigatus strains was studied. Glucose consumption was an excellent indicator of fungal growth. Second, the partial inhibition of growth was calculated in terms of the 90% or 50% inhibitory concentration for the 12 strains after treatment with itraconazole and amphotericin B. With a 3-day incubation time, the calculated 90% and 50% inhibitory concentrations agreed with those obtained by a macromethod and with those reported in previous publications. In each case the high degrees of efficacy of itraconazole and amphotericin B against A. fumigatus were confirmed. Partial inhibition induced by low concentrations of antifungal agents was quantifiable by this new method.
Selection and characterization of 5-fluoroorotate-resistant Plasmodium falciparum
Authors: Rathod P K , Khosla M , Gassis S , Young R D , Lutz C
Published: June 2012

Previous studies have shown that 100 nM 5-fluoroorotate (5-FO) is sufficient to block the in vitro proliferation of Plasmodium falciparum without causing toxicity to mammalian cells. In anticipation of potential drug resistance, a study was undertaken to identify P. falciparum cells that would proliferate in the presence of 5-FO. About 3 x 10(6) UV-irradiated as well as nonirradiated parasites were subjected to a one-step selection with 100 nM 5-FO both in the absence and in the presence of preformed pyrimidines (uracil, uridine, thymine, and thymidine). The P. falciparum cells that emerged after 3 weeks were cloned, and the 90% inhibitory concentration of 5-FO for the cloned cells was found to be 100- to 400-fold greater than that for the parent cell line. Two clones that were further characterized retained resistance to 5-FO even after prolonged propagation in culture without drug pressure. Since the mutants were not cross-resistant to 5-fluorouracil or to dihydrofolate reductase inhibitors, it was unlikely that alteration of thymidylate synthase or overproduction of the bifunctional dihydrofolate reductase-thymidylate synthase was responsible for 5-FO resistance. Similarly, resistance was not due to the expression of a pyrimidine salvage pathway since the cells were not pyrimidine auxotrophs, they did not show increased utilization of pyrimidine nucleosides, and they did not show increased susceptibility to 5-fluoropyrimidine nucleosides. When the selection experiments were repeated, without mutagenesis, in the presence of 10(-7) M 5-FO with fewer than 10(6) parasites or in the presence of more than 10(-7) M 5-FO with more than 10(8) parasites, viable mutants could not be recovered from the cultures. The implications of these findings for the in vivo use of 5-FO for malaria chemotherapy are discussed.
Susceptibilities to 10 antimicrobial agents of 1,220 Campylobacter strains isolated from 1987 to 1993 from feces of pediatric patients
Authors: Reina J , Ros M J , Serra A
Published: June 2012

We report the in vitro antibiotic susceptibility of 1,220 strains belonging to the thermotolerant Campylobacter species, isolated from the feces of pediatric patients with diarrhea in the period from 1987 to 1993. The strains were identified as 1,148 C. jejuni isolates and 72 C. coli isolates. The overall results show that the strains showed drug resistance as follows: 51.8% to ampicillin, 4.4% to clindamycin, 2.6% to chloramphenicol, 21.2% to tetracycline, and 1% to gentamicin. Twenty-one strains (1.7%) displayed resistance to the combination of amoxicillin-clavulanic acid, and 3.2% of the strains were resistant to erythromycin (MIC of > or = 4 micrograms/ml), with a notable difference according to the species under consideration. While C. jejuni remained stable at 0.9 to 4% resistance to erythromycin, for C. coli the percentages detected ranged from 0 to 33%, with overall rates of 2.5 and 15.2% for the two species, respectively. Resistance to nalidixic acid (MIC of > or = 32 micrograms/ml) was found in 27.2% of the strains (27.8% for C. jejuni and 18% for C. coli), and resistance to ciprofloxacin (MIC of > or = 4 micrograms/ml) was found in 24.2% of the strains for C. jejuni and 15.2% for C. coli). Cross-resistance between nalidixic acid and ciprofloxacin was found in 89.1% of the strains (type 1 mutants), while 10.9% were resistant to nalidixic acid but susceptible to ciprofloxacin (type 2 mutants).
Detection of aac(6')-I genes in amikacin-resistant Acinetobacter spp. by PCR
Authors: Ploy M C , Giamarellou H , Bourlioux P , Courvalin P , Lambert T
Published: June 2012

The distribution of aac(6')-I genes in 62 strains of Acinetobacter spp. resistant to amikacin, netilmicin, and tobramycin and susceptible to gentamicin, a phenotype compatible with synthesis of an AAC(6')-I enzyme, was studied by PCR and by DNA hybridization. Both methods gave similar results. Among the 51 Acinetobacter baumannii strains, aac(6')-Ib was found in 19 isolates and aac(6')-Ih was found in the remaining strains. The aac(6')-Ig gene was present in all 10 A. haemolyticus strains studied and was detected only in this species. A pair of degenerate oligonucleotides complementary to conserved regions of aac(6')-Ic, -Id, -If, -Ig, and -Ih enabled detection of these genes and also of aac(6')-Ij, recently recognized in Acinetobacter sp. strain 13.
Streptomycin resistance in mycobacteria
Authors: Honoré N , Cole S T
Published: June 2012

Streptomycin, the first antibiotic used in tuberculosis control programs, perturbs protein synthesis at the ribosome level. It is shown here that streptomycin resistance in some clinical isolates of Mycobacterium tuberculosis is associated either with missense mutations in the rpsL gene, which encodes ribosomal protein S12, or with base substitutions at position 904 in the 16S rRNA. The primary structure of the S12 protein is well conserved among the mycobacteria, even those, such as M. avium, M. gordonae, and M. szulgai, that are naturally resistant to streptomycin. This suggests that permeability barriers may be responsible for the resistance to the antibiotic.
Activity of fleroxacin alone and in combination with clindamycin or metronidazole in experimental intra-abdominal abscesses
Authors: Pefanis A , Thauvin-Eliopoulos C , Holden J , Eliopoulos G M , Ferraro M J , Moellering R C
Published: June 2012

To assess the potential efficacy of fleroxacin in combination with clindamycin or metronidazole in mixed aerobic and anaerobic infections, we used a rat model of intra-abdominal abscesses in which the inoculum consisted of pooled rat feces mixed with BaSO4. Two hours after bacterial challenge, antimicrobial therapy was begun intravenously with regimens designed to stimulate human pharmacokinetics. A combination of clindamycin and gentamicin was included as an established treatment regimen. After 8.5 days of therapy, final bacterial counts in abscesses showed that fleroxacin alone or combined with metronidazole or clindamycin effectively eradicated Escherichia coli, with bacterial densities of < or = 2.84 +/- 0.1, < or = 2.9 +/- 0.1, and < or = 2.9 +/- 0.1 (mean +/- standard error of the mean) log10 CFU/g, respectively. The addition of either clindamycin or metronidazole to fleroxacin substantially enhanced the effectiveness of the regimens against Bacteroides fragilis, with bacterial counts of < or = 3.0 +/- 0.1 or < or = 2.9 +/- 0.1 log10 CFU/g, respectively, versus 9.2 +/- 0.2 log10 CFU/g for fleroxacin alone. The combination of metronidazole and fleroxacin also resulted in a significantly greater reduction of peptostreptococci and Bacteroides thetaiotaomicron than fleroxacin alone (< or = 2.9 +/- 0.1 versus 6.1 +/- 0.9 log10 CFU/g and 3.3 +/- 0.4 versus 8.3 +/- 0.1 log10 CFU/g, respectively). Except for those of B. fragilis, counts of other anaerobes were reduced to a greater extent by metronidazole plus fleroxacin than by clindamycin plus fleroxacin, although differences were not always significant. Metronidazole plus fleroxacin was at least as active a clindamycin plus gentamicin against all species and was significantly more active against Clostridium spp. No regimen effectively eradicated enterococci from the abscesses. These results suggest that the addition of either metronidazole or clindamycin would effectively enhance the spectrum of fleroxacin for treatment of mixed aerobic and anaerobic infections.
In vitro and in vivo inhibition of ortho- and paramyxovirus infections by a new class of sulfonic acid polymers interacting with virus-cell binding and/or fusion
Authors: Ikeda S , Neyts J , Verma S , Wickramasinghe A , Mohan P , De Clercq E
Published: June 2012

A series of sulfonic acid polymers were shown to be potent and selective inhibitors of respiratory syncytial virus (RSV) and influenza A virus. The compounds inhibit the replication of RSV and influenza A virus in HeLa and MDCK cells, at concentrations of 0.16 and 4.0 micrograms/ml, respectively, and are nontoxic to growing cells at concentrations of > 100 micrograms/ml. The mode of antiviral action of the sulfonic acid polymers can be ascribed to inhibition of virus-cell fusion (for influenza A virus) or inhibition of both virus-cell binding and fusion (for RSV). The sulfonic acid prototype PAMPS [poly(2-acrylamido-2-methyl-1-propanesulfonic acid)], when administered intranasally to mice as a single dose of 10 or 50 mg per kg of body weight at the time of infection, completely inhibited influenza A virus replication (in lungs) and virus-associated lung consolidation in immunocompetent mice and completely protected NMRI and SCID (severe combined immune deficiency) mice against influenza A virus-associated mortality. When administered 1 h before or after virus inoculation, no protective effect was observed at a dose of 10 or 100 mg/kg. Sulfonic acid polymers exert selective inhibitory effects on RSV and influenza A virus replication.
Antiviral drug resistance mutations in human immunodeficiency virus type 1 reverse transcriptase occur in specific RNA structural regions
Authors: Schinazi R F , Lloyd R M , Ramanathan C S , Taylor E W
Published: June 2012

A statistically significant correlation exists between the locations of drug resistance mutations (DRMs) observed for various reverse transcriptase inhibitors and features of the secondary structure predicted for the RNA coding for human immunodeficiency virus type 1 reverse transcriptase. The known DRMs map onto "unstable" bases, which are predominantly nonhelical regions (i.e., loops, bulges, and bends) of the predicted RNA secondary structure, whereas codons for the key conserved residues of polymerase sequence motifs map onto "stable" paired bases involved in helical regions. On the basis of these results, we hypothesize that the secondary structure of the RNA template (in this case, the reverse transcriptase gene itself) may be a previously unrecognized factor contributing to base misincorporation errors during reverse transcription and that, rather than being randomly distributed, mutations are more likely to occur in specific regions of the genome. The results suggest that these "mutation-prone" regions can be predicted by using a standard algorithm for RNA secondary structure.
Treatment of murine candidiasis and cryptococcosis with amphotericin B incorporated into egg lecithin-bile salt mixed micelles
Authors: Brajtburg J , Elberg S , Travis S J , Kobayashi G S
Published: June 2012

Amphotericin B (AmB) with deoxycholate (Fungizone) and AmB incorporated into mixed micelles (AmB-mixMs) composed of egg lecithin with glycocholate, deoxycholate, or taurocholate were compared as treatments for murine infections. For mice infected with Candida albicans, treatment consisted of a single intravenous injection; for mice infected with Cryptococcus neoformans, treatment consisted of two intravenous injections. The maximal tolerated doses of AmB as Fungizone were 1.25 mg/kg of body weight in mice with candidiasis and 2.5 mg/kg of body weight in mice with cryptococcosis. The AmB-mixMs were nontoxic to mice at doses of 80 and 100 mg/kg of body weight and were therapeutically more active than the maximal tolerated dose of Fungizone in both models of infection. However, when Fungizone or AmB-mixMs were administered at equivalent doses of AmB, AmB-mixMs were more active in treating murine candidiasis, whereas Fungizone was more active in treating murine cryptococcosis.
In vivo activity of ajoene against rodent malaria
Authors: Perez H A , De la Rosa M , Apitz R
Published: June 2012

Ajoene (4,5,9-trithiadodeca-1,6,11-triene 9-oxide), a product initially isolated from extracts of garlic (Allium sativum), was tested for its antimalarial activity in vivo in a well-characterized murine model. A single ajoene dose of 50 mg/kg, on the day of infection, suppressed the development of parasitemia; there were no obvious acute toxic effects from the tested dose. The combination of ajoene (50 mg/kg) and chloroquine (4.5 mg/kg), given as a single dose on the day of the infection, completely prevented the subsequent development of parasitemia in treated mice.
Aerosolized amphotericin B-liposomes for treatment of systemic Candida infections in mice
Authors: Gilbert B E , Wyde P R , Lopez-Berestein G , Wilson S Z
Published: June 2012

Mice lethally infected with Candida albicans were exposed to small-particle aerosols containing amphotericin B-liposomes. The drug, when administered twice daily for 2 h (0.58 mg/kg of body weight per day) on days 1, 2, and 3 postinoculation, significantly reduced the numbers of Candida organisms in the kidneys. Aerosol treatment increased the survival time of mice given 2 2-h treatments once a week for 4 weeks. A twice-weekly, 2-h small-particle aerosol administration of amphotericin B-liposomes for 1, 2, or 3 weeks significantly increased both the mean time of survival and percent survival.
Physicochemical cell damage in relation to lethal amphotericin B action
Authors: Beggs W H
Published: June 2012

A direct relationship between the concentration-dependent rate of amphotericin B-induced K+ release from Candida albicans and the concentration-dependent rate of killing by the drug was established. This relationship together with the observed rapidity of both release and killing action supports the conclusion that the lethal action of amphotericin B is primarily physicochemical in nature.
In vitro susceptibility of the opportunistic fungus Cryptococcus neoformans to anthelmintic benzimidazoles
Authors: Cruz M C , Bartlett M S , Edlind T D
Published: June 2012

Ten benzimidazole derivatives and amphotericin B were tested in vitro against three isolates of Cryptococcus neoformans. Drug concentrations inhibiting 50% of growth (IC50s) were determined. Four derivatives, including mebendazole and albendazole, had moderately high activities (IC50 = 0.1 to 0.3 microgram/ml). Fenbendazole, however, was 10-fold more active (IC50 = 0.01 to 0.02 microgram/ml) and also 2-fold more active than amphotericin B. Ten additional clinical isolates of C. neoformans were tested against fenbendazole, mebendazole, and albendazole; similar susceptibilities were observed. Drug concentrations lethal to 90% of the cells (LC90s) were determined for two isolates. The LC90s of albendazole and mebendazole were 0.92 to 2.1 micrograms/ml, and those of fenbendazole were 0.06 to 0.07 microgram/ml; the latter are eight to ninefold lower than the LC90s of amphotericin B that were obtained. Spontaneously arising mutants displaying partial resistance to fenbendazole arose at a low frequency (5 x 10(-9).
Bactericidal activities of peptide antibiotics against multidrug-resistant Enterococcus faecium
Authors: Mobarakai N , Quale J M , Landman D
Published: June 2012

Multidrug-resistant Enterococcus faecium has emerged as a serious pathogen for which no effective therapy has been established. In this report, we describe the activities of two peptide antibiotics, ramoplanin and daptomycin, against 15 isolates of E. faecium resistant to vancomycin, ampicillin, and aminoglycosides using time-kill experiments. Both antibiotics were rapidly bactericidal when tested in broth; however, the addition of 50% serum resulted in significant regrowth. The combination of ampicillin with either ramoplanin or daptomycin largely prevented this regrowth. These peptide antibiotics showed good activity against these pathogens. While the development of daptomycin has been halted, ramoplanin may hold promise for the therapy of multidrug-resistant E. faecium, especially when combined with ampicillin.
Expression of reverse transcriptase from feline immunodeficiency virus in Escherichia coli
Authors: North T W , Hansen G L , Zhu Y , Griffin J A , Shih C K
Published: June 2012

Reverse transcriptase from feline immunodeficiency virus (FIV) has been cloned and expressed in Escherichia coli. We have purified this recombinant enzyme and shown that it is a 66-kDa protein that is indistinguishable from virion-derived FIV reverse transcriptase in sensitivity to the 5'-triphosphates of 3'-azido-3'-deoxythymidine and the four 2',3'-dideoxynucleosides. The availability of large quantities of the FIV reverse transcriptase will allow more detailed physical and pharmacological studies.
Inhibition of intracellular growth of Listeria monocytogenes by antibiotics
Authors: Michelet C , Avril J L , Cartier F , Berche P
Published: June 2012

We studied the activities of 15 antibiotics on the intracellular growth of Listeria monocytogenes in a HeLa cell line. After 24 h of contact with the infected cells, the antibiotics most effective against the intracellular growth of the 10 strains tested were amoxicillin, temafloxacin, and sparfloxacin, which nevertheless failed to totally eliminate the intracellular bacteria. Rifampin and co-trimoxazole had variable effects, depending on the isolates studied. The most active combinations were amoxicillin-sparfloxacin, co-trimoxazole-gentamicin, and sparfloxacin-co-trimoxazole. The results suggest the value of using a cell culture technique to study the activities of antibiotics against certain bacteria with intracellular sites of multiplication.