bluuebunny/crossref_metadata_2025 huggingface dataset:
Furazolidone and nitrofurantoin in the treatment of experimental Pneumocystis carinii pneumonia
Authors: Walzer P D , Kim C K , Foy J , Zhang J L
Published: June 2012

Furazolidone and nitrofurantoin, oral nitrofuran derivatives with broad-spectrum antimicrobial properties already in clinical use, were compared for activity against Pneumocystis carinii in an immunosuppressed rat model of P. carinii pneumonia. Furazolidone exhibited only slight activity as a prophylactic agent but was moderately effective in the therapy of pneumocystosis. The median histologic score and organism count fell from 4+ and 10(8) to 10(9) cysts per lung, respectively, in the controls to 1+ to 2+ and 10(7) to 10(8) cysts per lung, respectively, in the furazolidone-treated groups. However, these results were not as good as those obtained with the standard drug, trimethoprim-sulfamethoxazole (0+, 10(6) to 10(7) cysts per lung). Nitrofurantoin showed little anti-P. carinii activity despite different doses or drug preparations. The high doses of furazolidone used here and their toxic effects on the rats will probably discourage investigation of this drug in the treatment of pneumocystosis in humans. Nevertheless, since many nitrofurans have been synthesized, further exploration of this class of compounds might be helpful in developing new anti-P. carinii agents or in studying structure-activity relationships.
Effects of ciprofloxacin on plasmid DNA supercoiling of Escherichia coli topoisomerase I and gyrase mutants
Authors: Aleixandre V , Herrera G , Urios A , Blanco M
Published: June 2012

Changes in plasmid DNA supercoiling were measured following treatment of Escherichia coli cells, carrying topoisomerase mutations, with the quinolone ciprofloxacin. In quinolone-susceptible cells (top+ gyr+) as well as in topA mutants and in gyrB mutants, plasmid DNA was relaxed after the addition of ciprofloxacin. In cells partially resistant to quinolones, low ciprofloxacin levels led to an increase in negative superhelicity of plasmid DNA, whereas at higher ciprofloxacin concentrations, DNA became relaxed. Cells exhibiting partial resistance to quinolones carried either a gyrA mutation alone or a combination of gyrA and gyrB mutations. Moreover, they showed a reduction in gyrase activity, indicated by the supercoiling of a reporter plasmid. Therefore, we conclude that a low level of quinolone action and a DNA with a lower-than-normal level of superhelicity are the two essential conditions for obtaining a ciprofloxacin-promoted increase in plasmid DNA supercoiling. In contrast, deficiency in topoisomerase I is not required for this effect.
Delta pH-dependent accumulation of tetracycline in Escherichia coli
Authors: Yamaguchi A , Ohmori H , Kaneko-Ohdera M , Nomura T , Sawai T
Published: June 2012

The effects of ionophores on tetracycline accumulation in Escherichia coli cells were investigated in the presence of polymyxin B nonapeptide. Accumulation was inhibited by nigericin but not by valinomycin. Tetracycline accumulation was stimulated by decreasing the pH of the medium and inhibited by the addition of magnesium ions. These results indicated that tetracycline enters cells through diffusion as a protonated form (TH2) and is accumulated as a membrane-impermeable magnesium-tetracycline chelate complex (THMg+). This noncarrier diffusion hypothesis was confirmed by the fact that tetracycline accumulated in protein-free liposomes through an artificially imposed pH difference.
Inhibition of human immunodeficiency virus type 1 morphogenesis in T cells by alpha interferon
Authors: Smith M S , Thresher R J , Pagano J S
Published: June 2012

Some murine retroviruses exhibit altered release of virus when cells are treated with alpha interferon (IFN-alpha), resulting in the accumulation of intracellular virions in cytoplasmic vacuoles. In studies of the inhibitory effect of IFN-alpha (Wellferon) on acute human immunodeficiency virus type 1 infection of human T-cell lines, we found that in C3 cells, the 50% effective concentration was 9 U/ml and the 90% effective concentration was 310 U/ml. There was no apparent accumulation of intracellular particles detected by p24 antigen levels or by processing the cells for electron microscopy. Extracellular reverse transcriptase activity and p24 levels decreased in parallel with increasing IFN, whereas the intracellular viral proteins decreased only slightly. By electron microscopy, cells treated with higher concentrations of IFN (512 U/ml) disclosed very few particles budding into extracellular spaces; no intracellular particles could be seen, despite nearly normal levels of intracellular viral protein detected by the p24 antigen assay and correct processing detected by Western blot (immunoblot) analysis. Thus in human immunodeficiency virus-infected cells, the major block produced by IFN-alpha appeared to be late in the viral cycle at the morphogenesis stage of virion production. Chronically infected Jurkat cells treated with IFN appeared to be inhibited in growth rate, as virus production decreased proportionally with cell number.
Reevaluation of the factors involved in the efficacy of new beta-lactams against Enterobacter cloacae
Authors: Bellido F , Pechère J C , Hancock R E
Published: June 2012

The roles of outer membrane permeability, beta-lactamase stability, and inhibition of penicillin-binding proteins in the activity of new beta-lactams against Enterobacter cloacae were reappraised by using several methodological improvements. Outer membrane permeability in intact cells was determined by using a high-pressure liquid chromatography (HPLC)-based technique that avoided certain possible artifacts of the traditional methods. Vmax values were calculated from the numbers of enzyme molecules produced per cell and from catalytic constant (Kcat) values, which were obtained with purified beta-lactamase. Minimal periplasmic antibiotic concentrations needed to inhibit bacterial cell wall synthesis were estimated from the Zimmermann-Rosselet equation. All the beta-lactams tested formed relatively stable complexes with purified beta-lactamase. The antibiotics that exhibited low affinity for beta-lactamase apparently needed higher periplasmic concentrations to inhibit cell wall synthesis, suggesting a possible correlation between the affinity of beta-lactamase and the affinity of penicillin-binding proteins for the new beta-lactams. By using these estimates of outer membrane permeability, beta-lactamase hydrolysis, and cell wall-inhibiting concentrations, MIC could be theoretically predicted to within 1 dilution for five beta-lactams in three isogenic E. cloacae strains with differences in antibiotic susceptibility due to different porin or beta-lactamase contents.
Effect of dexamethasone or HWA-138 in combination with antibiotics in experimental Haemophilus influenzae type b infection
Authors: Rodriguez A F , Kaplan S L , Hawkins E P , Mason E O
Published: June 2012

Modulation of the host's inflammatory response in bacterial meningitis may be beneficial. In this study, the effects of dexamethasone and HWA-138, an analog of pentoxifylline, on CSF cultures and cochlear inflammation in an infant rat model of Haemophilus influenzae type b were studied. Five-day-old infant rats were inoculated once intraperitoneally with 1 x 10(4) to 10 x 10(4) CFU of H. influenzae type b (strain 1406). Twenty-four hours later, infant rats were treated intraperitoneally with one dose of ampicillin (0.1 mg/g of body weight), cefotaxime (0.05 mg/g), or cefuroxime (0.05 mg/g) alone or in combination with one dose of dexamethasone (0.00015 mg/g) or HWA-138 (0.005 mg/g). Twenty-four hours after treatment with cefuroxime plus dexamethasone, animals had a significantly (P less than or equal to 0.04) greater incidence of bacteremia and meningitis (eight of nine animals) than that in animals of the other treatment groups. Overall, dexamethasone was associated with less inflammation (P less than 0.04) of the cochlear nerve compared with that from antibiotic treatment alone. In this model, when suboptimal antimicrobial therapy is administered, anti-inflammatory agents may be beneficial with respect to reducing cochlear inflammation. However, dexamethasone and cefuroxime lead to a higher rate of positive blood and cerebral spinal fluid cultures than cefuroxime alone.
Efficacy of SCH 39304 in treatment of experimental invasive aspergillosis
Authors: Patterson T F , George D , Ingersoll R , Miniter P , Andriole V T
Published: June 2012

The efficacy of SCH 39304 (SCH) against Aspergillus fumigatus was assessed with an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Therapy with SCH at 10 or 15 mg/kg of body weight per day was begun 24 h after lethal challenge and compared with therapy with amphotericin B at 1.5 mg/kg/day. Compared with untreated controls, SCH reduced mortality and also reduced the tissue burden of A. fumigatus 100- to 1,000-fold in liver, kidney, and lung tissues. SCH at 15 mg/kg/day and amphotericin B eliminated A. fumigatus in liver, kidney, and lung tissues. In addition, both dosages of SCH significantly eliminated the organism from brain tissues, compared with controls. Both SCH and amphotericin B decreased or eliminated circulating aspergillus antigen. These results show that new azoles can be as effective as amphotericin B in eradicating the organism from tissues and offer promise in improving the treatment of invasive aspergillosis.
Characterization of erythromycin resistance in Campylobacter jejuni and Campylobacter coli
Authors: Yan W , Taylor D E
Published: June 2012

The mechanism of resistance to erythromycin, the drug of choice in the treatment of campylobacter gastroenteritis, was investigated. Erythromycin resistance (MICs, greater than 1,024 micrograms/ml) in three clinical isolates of Campylobacter jejuni and one C. coli isolate was determined to be constitutive and chromosomally mediated. In vivo protein synthesis in erythromycin-susceptible C. jejuni and C. coli strains was completely inhibited by low levels of erythromycin (5 micrograms/ml), whereas a high concentration of the antibiotic (100 micrograms/ml) had no effect on protein synthesis in erythromycin-resistant strains. Biological assays showed that extracellular degradation of erythromycin was not responsible for erythromycin resistance in strains of Campylobacter species. The rates and amounts of uptake of [14C]erythromycin by resistant and susceptible campylobacter cells were determined to be similar. Binding assays with purified campylobacter 70S ribosomes as well as 50S ribosomal subunits showed that those from erythromycin-resistant strans bound much less [14C]erythromycin than did those from susceptible strains. Genomic DNA from C. coli UA585 was used to transform erythromycin resistance to C. coli UA417. The erythromycin resistance marker was associated with a 240-kb SmaI fragment of the C. coli UA585 genome. Our results rule out erythromycin inactivation or efflux and are not consistent with the production of an RNA methylase, although they are consistent with a mutational mechanism of resistance due to a change in a ribosomal protein gene. This study constitutes a detailed biochemical and genetic characterization of erythromycin resistance in Campylobacter species.
Chlorhexidine resistance in methicillin-resistant Staphylococcus aureus or just an elevated MIC? An in vitro and in vivo assessment
Authors: Cookson B D , Bolton M C , Platt J H
Published: June 2012

Chlorhexidine (Hibiscrub; ICI) is generally accepted to be effective as an antiseptic hand wash for methicillin-susceptible Staphylococcus aureus (MSSA), but there is dispute whether the chlorhexidine MIC for methicillin-resistant S. aureus (MRSA) strains is higher than that for MSSA strains and, indeed, whether it is relevant. In addition, the link between resistance to chlorhexidine, gentamicin, and "nucleic acid-binding" compounds (NAB; which code, in particular, for propamidine isethionate and ethidium bromide) requires clarification. We performed chlorhexidine MIC and rate of kill tests on a number of MSSA and MRSA isolates. Two gentamicin-resistant MRSA isolates without NAB plasmids were more susceptible (0.25 and 0.5 microgram/ml) than four of eight MSSA that we tested (range, 0.25 to 2 microgram/ml). Chlorhexidine MICs were higher (4 to 8 micrograms/ml) for seven distinct MRSA isolates with plasmids conveying resistance to gentamicin and NAB (GNAB). Curing of the GNAB plasmid from MRSA strains resulted in a fall in the MIC (1 to 3.3 micrograms/ml), but no consistent fall in killing by chlorhexidine was observed. No effect on the chlorhexidine MIC or killing was observed when we cured strains of methicillin resistance. GNAB plasmid transfer resulted in a rise in the chlorhexidine MIC for the strains but not consistent fall in killing by chlorhexidine. Ethical approval was granted for 10 volunteers to each have a methicillin-susceptible, GNAB-resistant, derived transcipient and its GNAB-susceptible isogenic parent applied to separate sites in an in vivo skin test; no significant difference was seen in survival rates after the application of chlorhexidine. These results suggest that chlorhexidine appears to be as effective as a hand-washing agent for MRSA isolates with or with out NAB plasmids as it is for MSSA isolates.
Differential modulation of cytokine production by macrolides: interleukin-6 production is increased by spiramycin and erythromycin
Authors: Bailly S , Pocidalo J J , Fay M , Gougerot-Pocidalo M A
Published: June 2012

Antibiotics do not act alone but act in conjunction with the host defense system. In particular, it has been shown that some antibiotics can modify cytokine production. We compared the in vitro effects of three macrolides (roxithromycin, spiramycin, and erythromycin) actively concentrated by leukocytes on interleukin-1 alpha, (IL-1 alpha), IL-1 beta, IL-6, and tumor necrosis factor alpha production by human monocytes stimulated with lipopolysaccharide. Our results show that the three macrolides tested have different effects on production of these cytokines. Spiramycin and, to a lesser extent, erythromycin increased total IL-6 production without affecting IL-1 alpha, IL-1 beta, or tumor necrosis factor alpha production, whereas roxithromycin had no effect. To our knowledge, this is the first time that an antibiotic has been shown to increase IL-6 production.
Influence of albumin on itraconazole and ketoconazole antifungal activity: results of a dynamic in vitro study
Authors: Schäfer-Korting M , Korting H C , Amann F , Peuser R , Lukacs A
Published: June 2012

The relevance of intense protein binding to the antifungal activity of azole compounds is still a matter of debate. The influence of albumin on the antimicrobial activity of ketoconazole and itraconazole, which exhibit very strong plasma protein binding (99 and 99.8%), was evaluated in vitro. Candida albicans was exposed to continuously changing azole concentrations corresponding to drug levels in serum following an oral dose of 200 mg. Total as well as free drug levels in serum were simulated. The incubation medium was free of proteins or contained 4% human serum albumin. Itraconazole levels reflecting free drug concentrations in humans did not reduce the growth rate of C. albicans, as compared with controls (difference in the log CFU per milliliter at 12 h, 0.03 +/- 0.09), whereas total drug levels were as active in the presence of 4% albumin (mean difference, -0.61) as in its absence (-0.75). The same was true for ketoconazole, except that free drug levels were also active (-1.21 versus -1.39 for total drug levels). This result was due to the higher ketoconazole levels in humans. Thus, in terms of routine susceptibility testing, in vitro total drug levels can be considered relevant.
Effects of two cations on gastrointestinal absorption of ofloxacin
Authors: Martínez Cabarga M , Sánchez Navarro A , Colino Gandarillas C I , Domínguez-Gil A
Published: June 2012

A study was performed to establish the effect of Al3+ and Fe2+ cations on the absorption of ofloxacin when it is administered orally at a dose of 200 mg. The study was carried out with nine volunteers, who each received three treatments (A [200 mg of ofloxacin], B [200 mg of ofloxacin plus 11 g of colloidal aluminum phosphate], and C [200 mg of ofloxacin plus 1,050 mg of FeSO4]) according to a Latin square design; the washout period was 1 week. The analytical technique was a microbiological diffusion method. The pharmacokinetic parameters were calculated from the cumulative urinary excretion data and from a sigma-minus plot. The total amount of ofloxacin excreted in urine had a mean value of 163.59 +/- 22.13 mg when ofloxacin was administered alone, 152.41 +/- 18.76 mg when it was administered with Al3+, and 146.49 +/- 14.85 mg when it was administered with Fe2+. No statistically significant differences were found in the F values (fractions of dose absorbed) obtained with ofloxacin alone and ofloxacin plus Al3+ (P = 0.341). When ofloxacin alone was compared with joint administration with Fe2+ the value of F decreased 10.85%; this difference is statistically significant (P = 2.623 x 10(-2)).
Enantioselective disposition of ofloxacin in humans
Authors: Okazaki O , Kojima C , Hakusui H , Nakashima M
Published: June 2012

The enantioselective disposition of ofloxacin (OFLX) was studied in healthy subjects after oral administration of (+/-)-OFLX at a dose of 200 mg. S-(-)-OFLX and R-(+)-OFLX concentrations in serum and urine were measured separately by high-performance liquid chromatography, and various pharmacokinetic parameters were calculated from the data. The ratio of S-(-) to R-(+) enantiomer concentrations in serum showed a increase with time, with S/R ratios of 1.01 at 2 h and 1.31 at 24 h. The terminal elimination half-life of S-(-)-OFLX was 6.9 h, which was significantly greater (P less than 0.05) than that of the R-(+) enantiomer (6.3 h). S-(-)-OFLX also revealed a significantly greater area under the concentration-time curve in serum, mean residence time, and total body clearance than the R-(+) enantiomer did. The renal clearance of S-(-)-OFLX (7.14 liters/h/1.73 m2) was significantly lower than that of the R-(+) enantiomer (7.53 liters/h/1.73 m2). Although the difference in the pharmacokinetic parameters of the enantiomers was small, their disposition in humans was found to be stereoselective. The difference between the enantiomers may be explained by the difference in their renal excretion.
Hygromycin B therapy of a murine coronaviral hepatitis
Authors: Macintyre G , Curry B , Wong F , Anderson R
Published: June 2012

Hepatitis caused by mouse hepatitis virus (MHV-A59), a murine coronavirus, is accompanied by direct infection and replication of virus within the liver. We demonstrate here that the aminoglycoside hygromycin B is able to eliminate MHV-A59 infection from mouse peritoneal macrophages and cultured liver cells in vitro and is also able to reduce levels of virus replication and necrotic liver foci in vivo.
Comparative efficacies of amphotericin B lipid complex and amphotericin B deoxycholate suspension against murine blastomycosis
Authors: Clemons K V , Stevens D A
Published: June 2012

Amphotericin B as a lipid complex and as a deoxycholate suspension (Fungizone) was tested against murine blastomycosis. All doses of each form prolonged survival (P less than 0.05 to 0.001). Fungizone was more effective than lipid complex at doses of 0.8 mg/kg of body weight. However, lipid complex at 12.8 mg/kg was not toxic and superior in efficacy (P less than 0.001) to 2.0 mg of Fungizone per kg (a toxic dose), and it cleared all animals of infection. Lipid complex is an effective therapy for murine blastomycosis.
Ofloxacin penetration into tuberculous pleural effusion
Authors: Yew W W , Lee J , Chan C Y , Cheung S W , Wong P C , Kwan S Y
Published: June 2012

After 3 days of treatment with ofloxacin (300 mg given orally once daily), the drug levels in serum and pleural fluid 2 and 4 h after drug administration in patients with tuberculous pleural effusion were assessed by a rapid high-performance liquid chromatography assay. The levels in serum (mean +/- standard error of the mean [SEM]) were 4.70 +/- 0.14 and 4.63 +/- 0.09 mg/liter 2 and 4 h after administration, respectively, and the levels in pleural fluid (mean +/- SEM) were 3.82 +/- 0.09 and 4.21 +/- 0.08 mg/liter, respectively. The pleural fluid-to-serum ofloxacin ratio at 2 h was 0.82 +/- 0.02 (mean +/- SEM), and the ratio at 4 h was 0.92 +/- 0.02 (mean +/- SEM). This study demonstrated very good penetration of ofloxacin into pleural fluid in tuberculous pleuritis.
Subcellular distribution of gentamicin in proximal tubular cells, determined by immunogold labeling
Authors: Beauchamp D , Gourde P , Bergeron M G
Published: June 2012

The subcellular distribution of gentamicin in rat renal proximal tubular cells was evaluated by immunogold labeling. The distribution of the drug was monitored from 10 min to 10 days following single (40 mg/kg of body weight) and multiple (5 and 20 mg/kg/12 h) injections of gentamicin. Animals were killed on day 11, and cubes of renal cortex tissue were fixed overnight in cold phosphate-buffered glutaraldehyde (0.5%), dehydrated in ethanol, and embedded in Araldite 502 epoxy resin. Ultrathin sections were made and incubated with sheep antigentamicin and then with protein A-gold (15 nm) complex. At 10 min after a single injection, the labeling was found over the brush border membrane and over the membranes of endocytic apical vesicles of proximal tubular cells. After 1 h, a similar distribution was observed and the labeling was also seen over small lysosomes located close to the brush border membrane. At 24 h, gold particles were found over large lysosomes of proximal tubular cells. Following 10 days of treatment, lysosomes of proximal tubular cells were densely labeled with gold particles. The labeling was distributed uniformly over the lysosomes, although a lower density of labeling was observed over the myeloid bodies inside the lysosomes. Necrotic proximal tubular cells showed labeling over intact lysosomes and also in the cytoplasms of the cells, in the mitochondria, and in the nucleoli. The various control experiments demonstrated the high specificity of these results. The present immunocytochemical study better documents the subcellular disposition of gentamicin in proximal tubular cells, as previously evaluated by subcellular fractionation and autoradiography. This technique will be useful for better understanding the relationship between drug disposition and drug-induced toxicity.
In vitro and in vivo antifungal activities of BMY-28864, a water-soluble pradimicin derivative
Authors: Kakushima M , Masuyoshi S , Hirano M , Shinoda M , Ohta A , Kamei H , Oki T
Published: June 2012

BMY-28864, a water-soluble pradimicin derivative, had potent in vitro activity against a wide variety of fungi, including those associated with deep-seated mycosis; it inhibited the growth of standard strains and clinical isolates at concentrations of 12.5 micrograms/ml or less. At the MIC or higher concentrations, BMY-28864 was fungicidal for Candida albicans under both growing and nongrowing conditions. BMY-28864 expressed fungicidal activity only in the presence of Ca2+, and its activity was totally diminished when ethylene glycol-bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), a Ca2+ chelator, was added to the test medium. The effectiveness of intravenously administered BMY-28864 in vivo was examined and compared with that of amphotericin B in mouse models of fungal infections. Both normal and cyclophosphamide-treated immunosuppressed mice infected with C. albicans, Cryptococcus neoformans, or Aspergillus fumigatus responded to therapy with BMY-28864 (50% protective doses of 17, 18, and 37 mg/kg of body weight in normal mice and of 32, 35, and 51 mg/kg in cyclophosphamide-treated mice, respectively). Lethal lung infections were also established with C. albicans or A. fumigatus in cyclophosphamide-treated mice. The 50% protective doses of BMY-28864 were 15 and 23 mg/kg per dose against C. albicans and A. fumigatus, respectively. The immunosuppression induced by intraperitoneal administration of 200 mg of cyclophosphamide per kg lasted for 5 days, and total recovery was observed by day 7.
Antiviral and pharmacokinetic properties of C2 symmetric inhibitors of the human immunodeficiency virus type 1 protease
Authors: Kempf D J , Marsh K C , Paul D A , Knigge M F , Norbeck D W , Kohlbrenner W E , Codacovi L , Vasavanonda S , Bryant P , Wang X C
Published: June 2012

Specific processing of the human immunodeficiency virus (HIV) gag and gag-pol polyprotein gene products by the HIV protease is essential for the production of mature, infections progeny virions. Inhibitors of HIV protease block this maturation and thus prohibit the spread of HIV in vitro. Previously, we reported a series of novel, symmetric inhibitors of HIV protease designed to match the C2 symmetric structure of the active site of the enzyme. In response to the poor aqueous solubility of those lead compounds, we designed a series of analogs with substantially improved (greater than 10(4) fold) solubility. These inhibitors showed anti-HIV activity in H9 and MT4 cells at 0.05 to 10 microM, and in most cases, they were noncytotoxic at concentrations in excess of 100 microM. Further examination of one inhibitor (A-77003) revealed broad-spectrum activity against both HIV types 1 and 2, including azidothymidine-resistant HIV, in a variety of transformed and primary human cell lines. After administration of the inhibitors to rats, short half-lives and, with two notable exceptions, moderate oral bioavailability were observed. Additional pharmacokinetic studies in dogs and monkeys revealed the potential utility of A-77003 as an intravenous anti-HIV agent.
Crystal structure and molecular structure of mefloquine methylsulfonate monohydrate: implications for a malaria receptor
Authors: Karle J M , Karle I L
Published: June 2012

The crystal structure of (+/-)-mefloquine methylsulfonate monohydrate was determined by X-ray diffraction and was compared with the crystal structures of mefloquine hydrochloride and mefloquine free base. The conformation of mefloquine was essentially the same in all three crystalline environments and was not dependent on whether mefloquine was a salt or a free base. In mefloquine methylsulfonate monohydrate, the angle between the average plane of the quinoline ring and the average plane of the piperidine ring was 76.9 degrees. The intramolecular aliphatic N-13...O-1 distance was 2.730 +/- 0.008 A (1 A = 0.1 nm), which is close to the aliphatic N...O distance found in the antimalarial cinchona alkaloids. The hydroxyl group formed a hydrogen bond with the water molecule, and the amine group formed hydrogen bonds with two different methylsulfonate ions. The crystallographic parameters for (+/-)-mefloquine methylsulfonate monohydrate were as follows: C17H17F6N2O(+).CH3SO3(-).H2O; Mr = 492.4; symmetry of unit cell, monoclinic; space group, P2(1)/a; parameters of unit cell, a was 8.678 +/- 0.001 A, b was 28.330 +/- 0.003 A, c was 8.804 +/- 0.001 A, beta was 97.50 +/- 0.01 degrees; the volume of the unit cell was 2145.9 A3; the number of molecules per unit cell was 4; the calculated density was 1.52 g cm(-3); the source of radiation was Cu K alpha (lambda = 1.54178 A); mu (absorption coefficient) was 20.46 cm(-1); F(000) (sum of atomic scattering factors at zero scattering angle) was 1,016; room temperature was used; and the final R (residual index) was 6.58% for 1,740 reflections with magnitude of Fo greater than 3 sigma (F). Since the mechanism of antimalarial action and the mechanism of mefloquine resistance may involve hydrogen bond formation between mefloquine and a cellular effector or transport proteins, the common conformation of mefloquine found in each crystalline environment may define the orientation in which mefloquine forms these potentially critical hydrogen bonds with cellular constituents.
Effects of amphotericin B and fluconazole on the extracellular and intracellular growth of Candida albicans
Authors: van Etten E W , van de Rhee N E , van Kampen K M , Bakker-Woudenberg I A
Published: June 2012

The effects of amphotericin B and fluconazole on the extracellular and intracellular growth of Candida albicans were studied. With respect to the extracellular growth of C. albicans, antifungal activity was measured in terms of MICs and minimal fungicidal concentrations as well as by determination of the concentration that effectively killed (greater than 99.9%) C. albicans in the absence or presence (amphotericin B only) of serum. Amphotericin B was highly active in terms of killing, even at an increased inoculum size. In the presence of serum, amphotericin B activity was substantially reduced. For fluconazole, activity was restricted to inhibition of fungal growth, even after the inoculum size was reduced. With respect to the intracellular growth of C. albicans, antifungal activity was measured by using monolayers of murine peritoneal macrophages infected with C. albicans and was measured in terms of inhibition of germ tube formation as well as effective killing (greater than 99%) of C. albicans. Amphotericin B was highly active against C. albicans. At an increased ratio of infection, amphotericin B activity was slightly reduced. Fluconazole had no antifungal activity. Neither a reduction in the ratio of infection nor exposure of C. albicans to fluconazole prior to macrophage ingestion resulted in activity against intracellular C. albicans by fluconazole. Previous exposure of C. albicans to amphotericin B resulted in increased intracellular activity of amphotericin B. The intracellular antifungal activity of the combination of fluconazole with amphotericin B was less than that of amphotericin B alone. Amphotericin B showed fungicidal activity against C. albicans growing both extracellularly and intracellularly, whereas fluconazole inhibited growth only of extracellular C. albicans. A slight antagonistic effect between fluconazole and amphotericin B was found with respect to intracellular as well as extracellular C. albicans.
Molecular basis of tetracycline action: identification of analogs whose primary target is not the bacterial ribosome
Authors: Rasmussen B , Noller H F , Daubresse G , Oliva B , Misulovin Z , Rothstein D M , Ellestad G A , Gluzman Y , Tally F P , Chopra I
Published: June 2012

Tetracycline analogs fell into two classes on the basis of their mode of action. Tetracycline, chlortetracycline, minocycline, doxycycline, and 6-demethyl-6-deoxytetracycline inhibited cell-free translation directed by either Escherichia coli or Bacillus subtilis extracts. A second class of analogs tested, including chelocardin, anhydrotetracycline, 6-thiatetracycline, anhydrochlortetracycline, and 4-epi-anhydrochlortetracycline, failed to inhibit protein synthesis in vitro or were very poor inhibitors. Tetracyclines of the second class, however, rapidly inhibited the in vivo incorporation of precursors into DNA and RNA as well as protein. The class 2 compounds therefore have a mode of action that is entirely distinct from the class 1 compounds, such as tetracycline that are used clinically. Although tetracyclines of the second class entered the cytoplasm, the ability of these analogs to inhibit macromolecular synthesis suggests that the cytoplasmic membrane is their primary site of action. The interaction of class 1 and class 2 tetracyclines with ribosomes was studied by examining their effects on the chemical reactivity of bases in 16S rRNA to dimethyl sulfate. Class 1 analogs affected the reactivity of bases to dimethyl sulfate. The response with class 2 tetracyclines varied, with some analogs affecting reactivity and others (chelocardin and 4-epi-anhydrotetracycline) not.
Comparison of cefepime, cefpirome, and cefaclidine binding affinities for penicillin-binding proteins in Escherichia coli K-12 and Pseudomonas aeruginosa SC8329
Authors: Pucci M J , Boice-Sowek J , Kessler R E , Dougherty T J
Published: June 2012

The relative binding affinities of the extended-spectrum cephalosporins cefepime, cefpirome, and cefaclidine for the penicillin-binding proteins (PBPs) of Escherichia coli K-12 and Pseudomonas aeruginosa SC8329 were determined. Affinities were calculated from competition experiments between these antibiotics and [3H]benzylpenicillin in isolated membrane preparations. The concentrations which reduced binding to a PBP by 50% (IC50s) were determined. For E. coli, all three antibiotics displayed good PBP 3 binding (IC50s of 0.5 microgram/ml or less), and MICs roughly correlated with these values. Cefepime had a greater than 20-fold-lower IC50 for PBP 2 of E. coli than the other antibiotics. For P. aeruginosa, all of the antibiotics bound poorly (greater than 25 micrograms/ml) to PBP 2 but showed excellent pseudomonal (less than 0.0025 microgram/ml) PBP 3 binding. No correlations were seen between IC50s and MICs for P. aeruginosa. Despite differences in PBP binding, cefepime, cefpirome, and cefaclidine all displayed similar bactericidal activity for E. coli K-12 over the initial 3 h after antibiotic addition. All three caused E. coli to form filaments at values close to the MICs. In addition, cefepime induced "bleb" formation along the filaments at concentrations greater than 10x the MIC.
Temafloxacin pharmacokinetics in subjects with normal and impaired renal function
Authors: Granneman G R , Braeckman R , Kraut J , Shupien S , Craft J C
Published: June 2012

The pharmacokinetics of temafloxacin were investigated following oral administration of single 400-mg doses to 6 normal subjects and 18 subjects with various degrees of impaired renal function. Renal impairment did not significantly affect the peak concentration, time to peak concentration, or the nonrenal clearance of temafloxacin. Both renal clearance (CLR) and total apparent clearance (CLT/F, where F represents the fraction of dose absorbed) of temafloxacin were highly correlated with creatinine clearance (CLCR). The regression equations were as follows: CLR = 0.85.CLCR, with R2 = 0.907, and CLT/F = 56.0 + 0.92.CLCR, with R2 = 0.656. The half-life (mean +/- standard deviation) increased from 10.6 +/- 2.4 h in the normal volunteers to 24.6 +/- 7.3 h in the subjects with a CLCR of less than 10 ml/min; the respective CLT/F decreased from 169 +/- 58 to 70 +/- 27 ml/min. Compared with the CLT/F in the subjects with normal renal function, CLT/F was reduced 60% in subjects with a CLCR of less than 40 ml/min, indicating that the dosage should be reduced by at least one-half for patients with comparable impairment. For the subjects on chronic hemodialysis, most of the variability in the nonrenal clearance and the terminal-phase rate constant of temafloxacin was associated with the quantity of calcium carbonate and related medication taken for the treatment of hyperphosphatemia. Supplemental dosage is not required for patients undergoing hemodialysis, since the distribution of temafloxacin in tissue is extensive and the recoveries from 4-h dialysis sessions accounted for less than 10% of the drug present at the start of the dialysis.
Efficacy of chloramphenicol, enrofloxacin, and tetracycline for treatment of experimental Rocky Mountain spotted fever in dogs
Authors: Breitschwerdt E B , Davidson M G , Aucoin D P , Levy M G , Szabados N S , Hegarty B C , Kuehne A L , James R L
Published: June 2012

Dogs were experimentally inoculated with Rickettsia rickettsii to characterize the comparative efficacies of chloramphenicol, enrofloxacin, and tetracycline for the treatment of Rocky Mountain spotted fever (RMSF). All three antibiotics were equally effective in abrogating the clinical, hematologic, and vascular indicators of rickettsial infection. Antibiotic treatment for 24 h was sufficient to decrease the rickettsemia to levels below detection by Vero cell culture. Early treatment with all three antibiotics resulted in a similar decrease in antibody titer, but acute and convalescent serum samples taken at appropriate times would have still facilitated an accurate diagnosis of RMSF in all but one dog, which did not seroconvert. We conclude that chloramphenicol, enrofloxacin, and tetracycline are equally efficacious for treating experimental canine RMSF.
Isepamicin disposition in subjects with various degrees of renal function
Authors: Halstenson C E , Kelloway J S , Affrime M B , Lin C C , Teal M A , Shapiro B E , Awni W M
Published: June 2012

The disposition of isepamicin, an investigational aminoglycoside antibiotic, was evaluated in 30 subjects with various degrees of renal function. The subjects were divided into five groups: those with normal renal function (creatinine clearance [CLCR], greater than 80 ml/min/1.73 m2), those with mild renal insufficiency (CLCR, 50 to 80 ml/min/1.73 m2), those with moderate renal insufficiency (CLCR, 30 to 49 ml/min/1.73 m2), those with severe renal insufficiency (CLCR, 5 to 29 ml/min/1.73 m2), and those maintained on hemodialysis (CLCR, less than 5 ml/min/1.73 m2). Subjects on hemodialysis were studied both during hemodialysis and during an interdialytic period. The volumes of distribution of isepamicin were not significantly different among the five groups of patients. The total body clearance (CLP) and renal clearance (CLR) of isepamicin significantly decreased as CLCR decreased. The CLP of isepamicin and CLCR were significantly related [(COP = 0.391.[CLCR] + 1.83; r2 = 0.878)]. Nonrenal clearance of isepamicin did not differ between groups. Hemodialysis augmented the CLP of isepamicin by approximately 25-fold. The amount of isepamicin recovered in the dialysate was 60.6 +/- 15.8% of the dose administered. The maximal rebound of the isepamicin concentration in plasma after cessation of hemodialysis was observed at 0.78 +/- 0.7 h. Concentrations in plasma increased 32.7 +/- 22.9% over that measured at the end of hemodialysis. These data indicate that dosage adjustments are necessary in subjects with decreased renal function.
Antibiotic-induced release of endotoxin in chronically bacteriuric patients
Authors: Hurley J C , Louis W J , Tosolini F A , Carlin J B
Published: June 2012

A novel in vivo model for the study of antibiotic-induced release of endotoxin from gram-negative bacteria is described. The model uses the chronically colonized urinary tracts of patients whose spinal cords have been injured. At baseline, the organisms were present in the range of 1 x 10(3) to 2 x 10(7) CFU/ml, and the concentration of endotoxin ranged from 2 x 10(-1) to 1 x 10(3) ng/ml in 44 studies. In 10 control studies, the concentration of endotoxin and the numbers of viable gram-negative bacteria over time changed by an average of less than 0.15 log10 units from the baseline values. At 2 h after antibiotic administration, the average decrease in CFU was 0.93 log10 units, and because antibiotics cause the release of endotoxin, an average increase in endotoxin concentration of 0.59 log10 units was noted in 21 studies with susceptible bacteria. Similar changes in response to antibiotic exposure were seen in studies with susceptible Pseudomonas bacteria in comparison with those seen in studies with susceptible members of the family Enterobacteriaceae. These results provide evidence that this novel model may be useful for comparing the effects of antibiotics with different modes of action, both as single agents and in combination, on the concentration of endotoxin in relation to changes in the numbers of bacteria, under conditions of bacterial replication and antibiotic exposure more closely resembling those found in vivo than is possible in other models.
Influence of the unbound concentration of cefonicid on its renal elimination in isolated perfused rat kidneys
Authors: Rodriguez C A , Smith D E
Published: June 2012

The effect of variations in plasma protein binding on the renal excretion of cefonicid was assessed by using isolated perfused rat kidneys. Cefonicid exhibits preferential binding ex vivo to human serum albumin (HSA), as opposed to bovine serum albumin (BSA), and is eliminated mainly by tubular secretion, a process that was reported to be dependent on the total drug concentration. This contradicts previous studies with antimicrobial compounds and other drugs of low renal extraction in which the unbound drug concentration was shown to be the driving force for carrier-mediated tubular transport. To clarify this discrepancy, we performed perfusion studies by using 6% BSA at initial concentrations of 200 micrograms/ml (n = 6) and 20 micrograms/ml (n = 9) and in a combination of 4% BSA plus 2% HSA at initial concentrations of 200 micrograms/ml (n = 4). The excretion ratio [ER = CLR/(fu x GFR)] of cefonicid decreased with increasing unbound concentrations, whereas no apparent relationship with the total concentration was evident. At similar total concentrations of cefonicid, the renal clearance remained unchanged; the secretion clearance increased significantly in the 4% BSA-2% HSA experiments, reflecting the reduced unbound fraction and unbound drug concentration of cefonicid. The excretion ratio data were compatible with a model in which Michaelis-Menten kinetics were required to describe active transport and secretion was dependent on the unbound cefonicid concentration. As a result, changes in plasma protein binding as a result of drug interactions or disease states could significantly influence the tubular transport capability of compounds with low renal extraction.
Plasmid-mediated ROB-1 beta-lactamase in Pasteurella multocida from a human specimen
Authors: Rosenau A , Labigne A , Escande F , Courcoux P , Philippon A
Published: June 2012

A Pasteurella multocida human isolate was resistant to beta-lactams because of production of ROB-1 beta-lactamase. The beta-lactamase was encoded by a 4.3-kb plasmid closely related to that of a Pasteurella bovine strain, as shown by Sau3A restriction profile and hybridization with a plasmid probe containing the blaROB-1 gene.
Effect of protein binding of daptomycin on MIC and antibacterial activity
Authors: Lee B L , Sachdeva M , Chambers H F
Published: June 2012

A higher rate of clinical failures in patients treated with daptomycin (2 mg/kg of body weight, given once daily) compared with rates in patients treated with conventional regimens caused early termination of this comparative clinical trial. One explanation for these failures could be that daptomycin is highly protein bound and that the concentration of the unbound active drug is too low for antibacterial activity. To assess this explanation, we studied the binding of daptomycin to proteins by using an ultrafiltration method. pH (7.0 to 7.4), temperature (25 or 37 degrees C), or daily freezing and thawing over 2 months had no effect on binding of daptomycin to proteins. We found that daptomycin was bound to albumin (90%) at 4 g/100 ml. Binding of daptomycin was not concentration dependent (2.5 to 80 micrograms/ml). In human serum samples spiked with daptomycin, average binding was 94% +/- 2.4%. In 6 subjects given an intravenous infusion of daptomycin (3 mg/kg), average binding was 90% +/- 2.1%. Susceptibility studies showed that a concentration in serum 20 times the unbound concentration was needed to equal the MIC of the total drug. These results indicate that daptomycin is highly bound (90 to 94%) to albumin and that clinical failure to daptomycin can in part be explained by the low concentration of the unbound drug.
Mechanisms of amphotericin B-induced decrease in glomerular filtration rate in rats
Authors: Sabra R , Branch R A
Published: June 2012

Mechanisms responsible for the reductions in renal blood flow (RBF) and glomerular filtration rate (GFR) in response to acute infusions of amphotericin B were investigated in vivo in rats. The influence of salt status and the roles of adenosine, cyclic AMP, and calcium influx were examined. Amphotericin B was infused into the renal artery in seven groups of rats at 0.025 mg/kg of body weight per min for 15 min. RBF and GFR were measured over 15 min before, during, and after the infusion. Control rats were maintained on a normal salt diet; a second group of rats received a salt-depleted diet, and a third group received a high-salt intake. Four other groups were kept on a normal diet and received theophylline (0.5 mumol/kg/min into the renal artery, intra-arterially [i.a.]), dibutyryl cyclic AMP (85 micrograms/min, i.a.), the 5'-nucleotidase inhibitor adenosine alpha,beta-methylene diphosphate (4 mg/kg, intramuscularly), or diltiazem (20 micrograms/kg/min, i.a.). Control rats had a prompt 50% decrease in RBF in response to amphotericin B. This was sustained over the 15-min infusion period and was accompanied by a decrease in creatinine clearance (CLCR) (from 0.83 +/- 0.08 to 0.40 +/- 0.09 ml/min; P less than 0.05). On stopping the infusion, RBF returned quickly to baseline but CLCR continued to decrease further (to 0.35 +/- 0.07 ml/min; P less than 0.05). Salt loading, theophylline, and diltiazem administration prevented the decreases in both RBF and CLCR. Both RBF and CLCR responses in the remaining groups were not significantly different from those in controls. The results of this study reveal a protective effect of salt loading and theophylline against amphotericin B nephrotoxicity in the rat but deny a role for adenosine in mediating these effects. They further suggest that theophylline inhibits the acute responses by a mechanism unrelated to either adenosine receptor blockade or phosphodiesterase inhibition and that calcium influx into the cells is probably responsible for the acute changes in RBF and GFR in response to amphotericin B.
Isolation and characterization of Saccharomyces cerevisiae mutants resistant to aculeacin A
Authors: Font de Mora J , Gil R , Sentandreu R , Herrero E
Published: June 2012

Aculeacin A is a lipopeptide that inhibits beta-glucan synthesis in yeasts. A number of Saccharomyces cerevisiae mutants resistant to this antibiotic were isolated, and four loci (ACR1, ACR2, ACR3, and ACR4) whose products are involved in the sensitivity to aculeacin A of yeast cells were defined. Mutants containing mutations in the four loci were also resistant to echinocandin B, another member of this lipopeptide family of antibiotics. In contrast, acr1, acr3, and acr4 mutants were resistant to papulacandin B (an antibiotic containing a disaccharide linked to two fatty acid chains that also inhibits beta-glucan synthesis), but acr2 mutants were susceptible to this antibiotic. This result defines common and specific steps in the entry and action of aculeacin A and papulacandin B. The analysis of double mutants revealed an epistatic effect of the acr2 mutation on the other three mutations. Cell walls of the four different mutants did not show significant alterations in composition with respect to the parental strain, and in vitro glucan synthase activity was also unaffected. However, cell surface hydrophobicity in three of the mutants was considerably decreased with respect to the parental strain.