bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacies of piperacillin-tazobactam and cefepime in rats with experimental intra-abdominal abscesses due to an extended-spectrum beta-lactamase-producing strain of Klebsiella pneumoniae
Authors: Thauvin-Eliopoulos C , Tripodi M F , Moellering R C , Eliopoulos G M
Published: October 2018

The in vivo activities of piperacillin-tazobactam and cefepime were compared with those of ticarcillin-clavulanate, ceftazidime, cefotaxime, and imipenem in a rat model of intra-abdominal abscess with a strain of Klebsiella pneumoniae elaborating an extended-spectrum beta-lactamase (TEM-26). With the exception of ceftazidime, all of the antimicrobial agents significantly reduced bacterial counts within abscesses at the end of therapy compared with those in untreated controls. Residual viable cell counts (mean +/- standard deviation in log10 CFU/gram) were as follows: control, 8.76 +/- 0.97; ceftazidime, 8.00 +/- 0.76; piperacillin-tazobactam, 3.87 +/- 1.72; ticarcillin-clavulanate, 3.74 +/- 1.34; cefepime, 3.15 +/- 1.19; cefotaxime, 2.61 +/- 0.77; imipenem, 2.41 +/- 0.93. Imipenem was more effective than either of the inhibitor combinations (P < 0.05). Cefotaxime was unexpectedly effective given its poor in vivo activity against this organism in our earlier studies, which used a different dose and total duration of therapy (L. B. Rice, J. D. C. Yao, K. Klimm, G. M. Eliopoulos, and R. C. Moellering, Jr., Antimicrob. Agents Chemother. 35:1243-1244, 1991). These observations suggest that the effectiveness of cephalosporins in the treatment of experimental infections caused by extended-spectrum beta-lactamase-producing K. pneumoniae may be highly dependent on dosing regimens, even for a specific organism and site of infection.
Pharmacokinetics of gentamicin at traditional versus high doses: implications for once-daily aminoglycoside dosing
Authors: Demczar D J , Nafziger A N , Bertino J S
Published: October 2018

Two doses of gentamicin (2 and 7 mg/kg of body weight) were administered to 11 healthy volunteers in a randomized, crossover single-dose study to compare their pharmacokinetics. Doses were infused over 1 h with a syringe infusion pump, and 14 concentrations in sera were obtained over an 8-h period. Concentration in serum versus time data were fitted to a two-compartment pharmacokinetic model. In addition, to mimic the clinical setting, subjects' data were fitted by the Sawchuk-Zaske method. Distributional and postdistributional peak concentrations, along with the last obtained concentration in serum, were utilized to compare the following pharmacokinetic variables: volume of distribution at steady state (Vss), half-life, clearance (CL), and maximum concentration in serum (Cmax). With two-compartment pharmacokinetic fitting, significant differences in distribution half-life (average, 21.8 and 41.6 min [P < or = 0.05]) and gentamicin CL (76.6 +/- 6.6 and 67.2 +/- 4.2 ml/min/1.73 m2 [P < or = 0.001]) were found between traditional-dose and high-dose groups, respectively. When the data for concentrations in sera were fitted to a one-compartment pharmacokinetic model by using either the distributional or the postdistributional Cmax, statistically significant differences (P < or = 0.001) were found between Vss, half-life, CL, and Cmax values for both dosage groups. The results show that the pharmacokinetics of gentamicin at a large dose differ significantly from those at the traditional dose. This information has direct implications for once-daily aminoglycoside (ODA) literature when the Cmax values reported are distributional and therefore show falsely high Cmax/MIC ratio estimates. In addition, ODA nomogram dosing tools developed with distributional Cmax values are probably inaccurate.
Postantibiotic effect assessments for antibiotics exhibiting a wide range of bactericidal activities by using a modified total-cell-counting method
Authors: Li R C , Lee S W
Published: October 2018

We recently described a total-cell-counting method for postantibiotic effect (PAE) assessments that performs well with weakly bactericidal antibiotics. This note presents a modified method for the study of PAE with extended capability to cover a broad range of bactericidal activities.
Comparative in vitro activities of DU-6859a, levofloxacin, ofloxacin, sparfloxacin, and ciprofloxacin against 387 aerobic and anaerobic bite wound isolates
Authors: Goldstein E J , Citron D M , Hunt Gerardo S , Hudspeth M , Merriam C V
Published: October 2018

The activities of DU-6859a, levofloxacin, ofloxacin, sparfloxacin, and ciprofloxacin against bite wound isolates were determined by the agar dilution method. DU-6859a was the most active compound (MICs, < or = 0.125 microg/ml) against all Pasteurella species, Staphylococcus aureus, and streptococci; anaerobes were susceptible to < or = 0.5 microg/ml, except fusobacteria, which were susceptible to < or = 2 microg/ml. Against aerobes, levofloxacin was more active than ofloxacin (MIC at which 90% of isolates are inhibited [MIC90], < or = 1.0 microg/ml for both) and sparfloxacin and ciprofloxacin were also active (MIC90s, < or = 0.25 and < 1 microg/ml, respectively).
Modulation of the metabolism of beta-L-(-)-2',3'-dideoxy-3'-thiacytidine by thymidine, fludarabine, and nitrobenzylthioinosine
Authors: Rahn J J , Kieller D M , Tyrrell D L , Gati W P
Published: October 2018

beta-L-(-)-2',3'-Dideoxy-3'-thiacytidine (3TC) is a cytosine nucleoside analog that potently inhibits the replication of human and duck hepatitis B viruses and human immunodeficiency virus through the activity of its 5'-triphosphate ester metabolite. The present study examined the intracellular decay of 3TC 5'-phosphates and tested strategies for modulating the cellular content of those nucleotides in primary cultures of duck hepatocytes and in human hepatoma 2.2.15 cells and CCRF-CEM T lymphoblasts. Inhibition by deoxycytidine of the 5'-phosphorylation of 3TC in duck hepatocytes confirmed that, as in mammalian cells, deoxycytidine kinase catalyzed 3TC activation. The 5'-mono, 5'-di-, and 5'-triphosphates of 3TC underwent monoexponential elimination from duck hepatocytes and 2.2.15 cells (half-lives, 3.6 to 8.0 h). Thymidine and fludarabine, which are agents that enhance the activity of deoxycytidine kinase, were tested in strategies for increasing the cellular content of 3TC 5'-phosphates. Coordinate treatment of cells with 3TC and thymidine (50 microM) increased the content of 3TC 5'-monophosphate in duck hepatocytes and the content of 3TC 5'-di- and 5'-triphosphates in 2.2.15 cells, but enhancement of 3TC 5'-phosphate levels in CCRF-CEM cells required a higher thymidine concentration (100 microM). Fludarabine (5 microM) did not affect the contents of 3TC 5'-di- and 5'-triphosphates in duck hepatocytes, but modestly increased the contents of those nucleotides in 2.2.15 cells and CCRF-CEM cells. Nitrobenzylthioinosine (NBMPR), an inhibitor of the es facilitated diffusion nucleoside transporter, reduced the level of entry of 3TC into 2.2.15 cells and abolished inward fluxes of thymidine, adenosine, and deoxycytidine. In 2.2.15 cells and CCRF-CEM cells, NBMPR reduced the formation of 3TC 5'-di- and 5'-triphosphates and reversed the thymidine- and fludarabine-induced increases in the formation of those nucleotides. NBMPR protected against the cytotoxicity of 3TC in CCRF-CEM cells, whereas thymidine potentiated that toxicity, apparently by enhancing the formation of 3TC 5'-triphosphate. Taken together, these results indicate that deoxycytidine kinase and the es nucleoside transporter are targets for manipulation of the metabolism and activity of 3TC.
Ginseng treatment reduces bacterial load and lung pathology in chronic Pseudomonas aeruginosa pneumonia in rats
Authors: Song Z , Johansen H K , Faber V , Moser C , Kharazmi A , Rygaard J , Høiby N
Published: October 2018

The predominant pathogen in patients with cystic fibrosis (CF) is Pseudomonas aeruginosa, which results in a chronic lung infection associated with progressive pulmonary insufficiency. In a rat model of chronic P. aeruginosa pneumonia mimicking that in patients with CF, we studied whether the inflammation and antibody responses could be changed by treatment with the Chinese herbal medicine ginseng. An aqueous extract of ginseng was injected subcutaneously, and cortisone and saline were used as controls. Two weeks after challenge with P. aeruginosa, the ginseng-treated group showed a significantly improved bacterial clearance from the lungs (P < 0.04), less severe lung pathology (P = 0.05), lower lung abscess incidence (P < 0.01), and fewer mast cell numbers in the lung foci (P < 0.005). Furthermore, lower total immunoglobulin G (IgG) levels (P < 0.01) and higher IgG2a levels (P < 0.025) in serum against P. aeruginosa sonicate and a shift from an acute type to a chronic type of lung inflammation compared to those in the control and cortisone-treated groups were observed. These findings indicate that ginseng treatment of an experimental P. aeruginosa pneumonia in rats promotes a cellular response resembling a TH1-like response. On the basis of these results it is suggested that ginseng may have the potential to be a promising natural medicine, in conjunction with other forms of treatment, for CF patients with chronic P. aeruginosa lung infection.
Antimicrobial effects of continuous versus intermittent administration of carbapenem antibiotics in an in vitro dynamic model
Authors: Keil S , Wiedemann B
Published: October 2018

In an in vitro dynamic model we compared the antimicrobial effects of two carbapenems, imipenem (MIC, 1 microg/ml) and meropenem (MIC, 0.25 microg/ml) on Pseudomonas aeruginosa. The antibiotics were administered either as short-time infusions once or three times a day or as continuous infusions with steady-state levels ranging from 0.5 to 20 microg/ml. From the resulting kill curves the period of time until the onset of bacterial death (dt), the rate constant of bacterial death (ka), the maximal reduction of CFU (mr), and the period of time until bacterial regrowth occurred (tr) were determined. Additionally, the occurrence of bacterial resistance during the simulations (rq) and the postantibiotic effect (PAE) were recorded. For both investigated carbapenems no significant difference in dt, ka, mr, and PAE values between the short-time infusions and continuous infusions with steady-state levels above 2 microg/ml could be detected. The tr was longest with continuous infusions of over approximately 24 h, corresponding to steady-state levels of 3 microg/ml for imipenem and 2.5 microg/ml for meropenem. An increase in MIC was observed only during continuous infusions with steady-state levels below 2 microg/ml. Independent of the chosen method of application and despite the lower MIC of meropenem, imipenem was slightly more effective than meropenem.
Effects of drugs on 2',3'-dideoxy-2',3'-didehydrothymidine phosphorylation in vitro
Authors: Hoggard P G , Kewn S , Barry M G , Khoo S H , Back D J
Published: October 2018

Drugs commonly administered to patients infected with the human immunodeficiency virus (HIV) have been studied for their propensity to alter the intracellular phosphorylation of the anti-HIV nucleoside analog stavudine (2',3'-dideoxy-2',3'-didehydrothymidine; d4T) in peripheral blood mononuclear cells (PBMCs) and U937 cells in vitro. PBMCs isolated from the blood of healthy volunteers were stimulated by the mitogen phytohemagglutinin (10 microg/ml) for 72 h. Stimulated PBMCs (3 x 10(6) cells/plate) were then incubated with [3H]d4T (0.65 microCi; 3 microM) and either acyclovir, dapsone, ddC, ddI, fluconazole, foscarnet, ganciclovir, itraconazole, lobucavir, ranitidine, ribavirin, rifampin, sorivudine, sulfamethoxazole, trimethoprim, lamivudine (3TC), zidovudine, or thymidine (30 and 300 microM) for 24 h. Doxorubicin and drugs showing some evidence of inhibition were also studied at 0.3 and 3 microM. Cells were extracted overnight with 60% methanol prior to analysis by radiometric high-performance liquid chromatography. Additional data for nine of the drugs were obtained by incubation with [3H]d4T in U937 cells for 24 h. The effect of d4T (0.2 to 20 microM) on zidovudine (0.65 microCi; 0.018 microCi) phosphorylation was also studied. Zidovudine significantly reduced d4T total phosphates in PBMCs and U937 cells (in PBMCs to 33% [P < 0.001] and 17% [P < 0.001] of that in control cells at 3 and 30 microM, respectively). A small reduction in zidovudine phosphorylation was seen with d4T but only at d4T:zidovudine ratios of 100 and 1,000. Of the other compounds screened, only thymidine, ribavirin, and doxorubicin produced inhibition of d4T phosphorylation in both PBMCs and U937 cells. However, doxorubicin was cytotoxic at 3 microM. The decrease in d4T phosphorylation in the presence of ribavirin is consistent with previous findings with zidovudine. Although ddC significantly inhibited the phosphorylation of d4T in PBMCs, this was not seen in U937 cells, and it is probable that the findings in PBMCs are related to mitochondrial toxicity [based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity assay]. The only drugs screened which may interfere with d4T phosphorylation at clinically relevant concentrations were zidovudine, ribavirin, and doxorubicin.
Comparison of recalcitrance to ciprofloxacin and levofloxacin exhibited by Pseudomonas aeruginosa bofilms displaying rapid-transport characteristics
Authors: Vrany J D , Stewart P S , Suci P A
Published: October 2018

Attenuated total reflection Fourier transform infrared spectroscopy was used to measure transport of the fluoroquinolones (FQs) ciprofloxacin and levofloxacin into Pseudomonas aeruginosa biofilms. Biofilms were exposed to each FQ at dose levels of 100, 250, and 500 microg/ml for 30 min. A mathematical transport model was used to extract the diffusion coefficient, binding site density, and adsorption and desorption rates for each experiment. Recalcitrance of the biofilms toward each FQ was evaluated by comparison of efficacies with planktonic bacteria. By this criterion, biofilms were found to exhibit more recalcitrance toward levofloxacin than ciprofloxacin under the experimental conditions. These results cannot be explained by the more hindered transport of levofloxacin, implicating the domination of physiological factors.
Pharmacodynamics of RP 59500 (quinupristin-dalfopristin) administered by intermittent versus continuous infusion against Staphylococcus aureus-infected fibrin-platelet clots in an in vitro infection model
Authors: Rybak M J , Houlihan H H , Mercier R C , Kaatz G W
Published: October 2018

We evaluated the bactericidal activity of RP 59500 (quinupristin-dalfopristin) against fibrin-platelet clots (FPC) infected with two clinical isolates of Staphylococcus aureus, one constitutively erythromycin and methicillin resistant (S. aureus AW7) and one erythromycin and methicillin susceptible (S. aureus 1199), in an in vitro pharmacodynamic infection model. RP 59500 was administered by continuous infusion (peak steady-state concentration of 6 microg/ml) or intermittent infusion (simulated regimens of 7.5 mg/kg of body weight every 6 h (q6h) q8h, and q12h. FPCs were infected with S. aureus to achieve an initial bacterial density of 10(9) CFU/g. Model experiments were run in duplicate over 72 h. Two FPCs were removed from each model at 0, 12, 24, 36, 48, and 72 h, and the bacterial densities (in CFU per gram) were determined and compared to those of growth control experiments. Additional samples were also removed from the model over the 72-h period for pharmacokinetic evaluation. All regimens significantly (P < or = 0.01) decreased bacterial densities in the infected FPCs for both isolates compared to growth controls. This occurred even though MBCs were equal to or greater than the RP 59500 concentrations achieved in the models. There were no significant differences found between the dosing frequencies and levels of killing when examining each isolate separately. However, examination of the residual bacterial densities (CFU per gram at 72 h) and visual inspection of the overall killing effect (killing curve plots over 72 h) clearly demonstrated a more favorable bactericidal activity against 1199 than against the AW7 isolate. This was most apparent when the q8h and the q12h AW7 regimens were compared to all 1199 treatment regimens by measuring the 72-h bacterial densities (P < or = 0.01). Killing (99.9%) was not achieved against the AW7 isolate. However, a 99.9% kill was demonstrated for all dosing regimens against the 1199 isolate. The area under the concentration-time curve from 0 to 24 h was found to be significantly correlated with reduction in bacterial density for the AW7 isolate (r = 0.74, P = 0.04). No resistance was detected during any experiment for either isolate. RP 59500 efficacy against constitutively erythromycin- and methicillin-resistant S. aureus may be improved by increasing organism exposure to RP 59500 as a function of dosing frequency.
Candida norvegensis: a fluconazole-resistant species
Authors: Sandven P , Nilsen K , Digranes A , Tjade T , Lassen J
Published: October 2018

Candida norvegensis has been an unusual cause of infections in humans. In Norway this species was isolated from eight patients from 1990 to 1996 and was of probable pathogenic significance in four of them. All isolates were resistant to fluconazole. The same was true for two C. norvegensis isolates from before 1940, and it is therefore assumed that the fluconazole resistance is inherent.
In vitro reduction of endotoxin concentrations with the 5S fragment of immunoglobulin G
Authors: Xuan D , Nicolau D P , Tessier P R , Bow L , Quintiliani R , Nightingale C H
Published: October 2018

Endotoxin has long been implicated as an inducer for the development and progression of gram-negative sepsis. Accordingly, antiendotoxin therapy has been considered one of the major targets for the treatment of sepsis. To investigate the influence of a human immunoglobulin G (IgG) derivative, the 5S fragment of IgG (5S-IgG; Gamma-Venin, Centeon Pharma GmbH, Frankfurt-Niederrad, Germany), on endotoxin release during bacterial proliferation and under antibiotic bactericidal action, time-kill studies were performed by using Escherichia coli ATCC 25922 starting inocula of 10(3), 10(5), and 10(7) CFU/ml with cefotaxime (120 microg/ml) alone and in combination with 5S-IgG (2,100 microg/ml). Samples were collected for bacterial colony count and endotoxin concentration determinations; the area under the free endotoxin concentration curve (AUFEC) was calculated by using the trapezoidal rule. Colony counts showed that cefotaxime had a rapid bactericidal effect because it achieved greater than a 4-log decrease in the numbers of E. coli CFU per milliliter over the first 2 h; the addition of 5S-IgG did not appear to alter the kinetics of killing. Comparison of the AUFEC revealed that the addition of 5S-IgG resulted in a mean reduction of 50, 66, and 27% in the free endotoxin concentration at starting inocula of 10(3), 10(5), and 10(7) CFU/ml, respectively. Moreover, experiments were conducted with a starting inoculum of 10(5) CFU/ml and various amounts of 5S-IgG (2 to 20 mg/ml) to further investigate the dose-effect relation of 5S-IgG on endotoxin release. Decreased AUFECs were observed with increasing concentrations of 5S-IgG, suggesting the dose-dependent antiendotoxin activity of 5S-IgG. Further study is required to investigate the mechanism(s) responsible for this observation, the biological significance of this antiendotoxin activity, and the potential utility of 5S-IgG as an adjuvant therapy in the treatment of gram-negative sepsis.
Activity of the triazole SCH 56592 against disseminated murine coccidioidomycosis
Authors: Lutz J E , Clemons K V , Aristizabal B H , Stevens D A
Published: October 2018

SCH 56592 (SCH) is a new triazole antifungal with a broad spectrum of activity. In vitro susceptibility testing against five strains of Coccidioides immitis revealed MICs from 0.39 to 3.13 microg/ml and minimal fungicidal concentrations from 1.56 to 3.13 microg/ml. A murine model of systemic coccidioidomycosis was established in female CD-1 mice. Groups received either no treatment or oral therapy with fluconazole at 10 or 100 mg/kg of body weight; itraconazole at 10 or 100 mg/kg; SCH at 0.5, 2, 10, or 25 mg/kg; or its methylcellulose diluent alone. Therapy began 2 days postinfection and continued once daily for 19 days. Surviving mice were euthanized 49 days postinfection, and infectious burdens were determined by culture. All drugs were superior to no-treatment or diluent-treatment controls (P < 0.001) in prolonging survival but were not significantly different from one another. Itraconazole at 100 mg/kg was superior to fluconazole in reduction of CFU in the spleen, liver, and lung (P < 0.01 to 0.001). SCH at 0.5 mg/kg was superior to either fluconazole or itraconazole at 10 mg/kg in reduction of CFU in all three organs (P < 0.05 to 0.001). SCH at 2 mg/kg was not significantly different from itraconazole at 100 mg/kg in all three organs. SCH at 10 and 25 mg/kg was superior to either dose of fluconazole or itraconazole in all three organs (P < 0.05 to 0.001). In terms of reduction of CFU, SCH was > or = 200-fold as potent as fluconazole and > or = 50-fold as potent as itraconazole. There was a clear dose-responsive relationship for SCH in each of the organs. It is noteworthy that SCH effected cures (no detectable C. immitis in any organ) in 1 of 9, 6 of 10, or 9 of 9 surviving mice in animals given 2, 10, or 25 mg/kg, respectively. Neither fluconazole nor itraconazole cured any survivor. SCH has potent, fungicidal activity in vivo against C. immitis. It should be considered for clinical trials in patients with coccidioidomycosis.
Cross-resistance associated with development of resistance to isometamidium in a clone of Trypanosoma congolense
Authors: Peregrine A S , Gray M A , Moloo S K
Published: October 2018

Resistance to isometamidium was increased 94-fold in a clone of Trypanosoma congolense (clone IL 1180) by repeated subcurative treatment of infected mice for 11 months. This was associated with 3.4-, 33-, and 4.2-fold increases in resistance to diminazene, homidium, and quinapyramine, respectively. Both T. congolense IL 1180 and the resistant derivative were able to undergo cyclical development in Glossina morsitans centralis tsetse flies, producing hypopharyngeal infection rates of 40.0 and 39.8%, respectively.
Assessment of biliary excretion of piperacillin-tazobactam in humans
Authors: Westphal J F , Brogard J M , Caro-Sampara F , Adloff M , Blicklé J F , Monteil H , Jehl F
Published: October 2018

Piperacillin-tazobactam concentrations in serum and bile were measured intraoperatively in 10 patients undergoing cholecystectomy (group 1) and 5 cholecystectomized patients provided with external bile duct drainage (group 2). Each patient received a single intravenous dose of piperacillin at 4 g plus tazobactam at 0.5 g over 30 min. Drug concentrations in both serum and bile were measured by high-performance liquid chromatography. In group 1 patients, serum and bile specimens and gallbladder wall fragments were collected at mean times of 70 and 83 min postinfusion, respectively. The mean concentrations of piperacillin and tazobactam were, respectively, 69.1 +/- 41.5 (standard deviation) and 9.9 +/- 5.1 microg/ml in serum, 630.4 microg/ml (range, 24.8 to 1,194 microg/ml) and 11.8 microg/ml (range, 3.6 to 22 microg/ml) in choledochal bile, 342.3 microg/ml (range, 1.1 to 1,149 microg/ml) and 7.7 microg/ml, (range, 0.2 to 23.1 microg/ml) in gallbladder bile, and 49.3 microg/g (range, 9.7 to 223 microg/g) and 2.9 microg/g (range, 0.1 to 5.9 microg/g) in the gallbladder wall. In group 2 patients, the amounts of drugs recovered in bile drainage obtained over 12 h were 28.4 +/- 18.0 and 1.0 +/- 0.5 mg for piperacillin and tazobactam, respectively. Peak piperacillin and tazobactam concentrations in bile reached 358 +/- 242 and 10.8 +/- 4.2 microg/ml, respectively. Comparison of drug levels in serum and bile suggests an underlying active secretion process for piperacillin elimination into the bile, unlike that of tazobactam. From a therapeutic viewpoint, given the concentrations of tazobactam recorded in bile fluid and tissue, the addition of this beta-lactamase inhibitor to piperacillin therapy might be of interest in the management of biliary tract infections, mostly in patients at risk of mixed aerobic-anaerobic infections due to beta-lactamase-producing organisms.
Pharmacokinetics of sparfloxacin and interaction with cisapride and sucralfate
Authors: Zix J A , Geerdes-Fenge H F , Rau M , Vöckler J , Borner K , Koeppe P , Lode H
Published: October 2018

In an open, randomized, triple crossover study, the effects of cisapride and sucralfate on the pharmacokinetics of sparfloxacin were assessed. Fifteen healthy volunteers received 400 mg of sparfloxacin as a single oral dose on day 0. In a random order, concomitant doses of 10 mg of cisapride three times daily from day -2 to day 2 and 1 g of sucralfate four times daily from day -2 to day 0 were administered. Sparfloxacin concentrations were measured by bioassay and high-performance liquid chromatography. Pharmacokinetic parameters for sparfloxacin alone were as follows (mean +/- standard deviation): maximum concentration of drug in serum (C(max)), 1.27 +/- 0.39 microg/ml; time to C(max) (T(max)), 4.1 +/- 1.9 h; area under the concentration-time curve (AUC), 35.0 +/- 9.7 microg x h/ml; mean residence time, 28.5 +/- 5.7 h; half-life (t1/2), 20 +/- 4 h; urinary recovery (UR x f), 11.0% +/- 2.7%; and metabolite-sparfloxacin ratio in urine, 2.6. For the cisapride group there was a significant decrease in the sparfloxacin T(max) (1.9 +/- 2.1 h) and a significant increase in C(max) (1.74 +/- 0.73 microg/ml). The QTc interval for patients receiving sparfloxacin and cisapride was prolonged by 7.7% compared to the QTc interval during medication-free periods. Significant differences in the values for the group receiving sucralfate compared to the values for the group receiving sparfloxacin alone were found: C(max), 0.77 +/- 0.31 microg/ml; AUC, 18.6 +/- 5.8 microg x h/ml; t1/2, 26 +/- 10 h; and UR x f, 5.8 +/- 1.8%. Concomitant adminstration of cisapride accelerates the absorption and increases the peak concentration of sparfloxacin without having a significant effect on the extent of bioavailability. Coadministration of sucralfate leads to a 44% decrease in the bioavailability of sparfloxacin.
Use of Toxoplasma gondii expressing beta-galactosidase for colorimetric assessment of drug activity in vitro
Authors: McFadden D C , Seeber F , Boothroyd J C
Published: October 2018

A microtiter assay for drug evaluation has been developed with a strain of Toxoplasma gondii that expresses bacterial beta-galactosidase. By using chlorophenol red-beta-D-galactopyranoside (CPRG) as the substrate for beta-galactosidase, the efficacy of a drug against the parasite can be determined with a colorimetric readout. Drugs known to have activity against T. gondii (specifically, pyrimethamine, sulfadiazine, atovaquone, and clindamycin) were tested, and efficacies were determined by CPRG cleavage. The 50% inhibitory concentrations determined by the CPRG-based colorimetric assay were similar to those determined by the traditional radiolabelled uracil incorporation assay. Since CPRG is nontoxic to the parasite, viable drug-treated parasites can be obtained at the conclusion of the assay for further evaluation if desired. This assay provides a high-throughput and nonradioactive alternative for the identification of anti-T. gondii compounds.
Enterococcal transposon Tn5384: evolution of a composite transposon through cointegration of enterococcal and staphylococcal plasmids
Authors: Bonafede M E , Carias L L , Rice L B
Published: October 2018

Mechanisms for the possible transfer of antimicrobial resistance genes between staphylococci and enterococci remain poorly defined. We have previously reported the transfer between Enterococcus faecalis strains of a multiresistance chromosomal element (beta-lactamase positive and resistance to erythromycin, gentamicin, mercuric chloride, streptomycin, and tetracycline) which we have tentatively designated Tn5385. Tn5385 is a composite of several smaller transposable elements, including Tn5384, a 26-kb composite transposon conferring resistance to erythromycin, gentamicin, and mercuric chloride. Analyses of 7 kb within Tn5384 and flanking sequences within the larger element revealed sequences characteristic of staphylococcal beta-lactamase and small, mobilizable plasmids flanking a region with a sequence identical to those of the replication genes previously described for enterococcal and streptococcal broad-host-range plasmids. These diverse regions are linked by insertion sequences IS256 and IS257 in a manner which suggests a series of cointegration events as the genesis of the current relationship. Taken together, these data suggest that Tn5384 and the larger element within which it is incorporated (Tn5385) evolved at least in part as a result of cointegration between an enterococcal broad-host-range plasmid and staphylococcal beta-lactamase and small mobilizable plasmids. These results implicate broad-host-range plasmids in the transfer of resistance determinants from staphylococci to enterococci.
Physical characteristics and lipoprotein distribution of liposomal nystatin in human plasma
Authors: Wasan K M , Ramaswamy M , Cassidy S M , Kazemi M , Strobel F W , Thies R L
Published: October 2018

The physical characteristics and lipoprotein distribution of free nystatin (NYS) and liposomal NYS (L-NYS) in human plasma were investigated. To determine the percentage of NYS that was lipid associated following incubation in human plasma, C18 reverse-phase extraction columns were used. To assess plasma drug distribution, NYS and L-NYS (20 microg/ml) were incubated in human plasma for 5, 60, and 120 min at 37 degrees C. After each interval, plasma was removed and separated into its lipoprotein and lipoprotein-deficient plasma (LPDP) fractions by ultracentrifugation and assayed for NYS by high-pressure liquid chromatography. Further studies evaluated the liposome structure of L-NYS by filtering through a 0.14-microm-pore-size microfilter before and after the addition of human plasma. When reconstituted L-NYS (mean particle diameter +/- standard deviation, 321 +/- 192 nm) was applied to a C18 column, 67% +/- 4% of the initial NYS concentration was associated with the lipid. When plasma samples containing L-NYS that had been incubated for 5 to 120 min at 37 degrees C were applied to C18 columns, 66 to 76% of the NYS was lipid associated. Incubation of NYS in human plasma for 5 min at 37 degrees C resulted in 3% +/- 1% of the initial NYS concentration incubated in the low-density lipoprotein (LDL) fraction, 23% +/- 4% of that in the high-density lipoprotein (HDL) fraction, and 66% +/- 10% of that in the LPDP fraction. In contrast, the distribution of NYS following incubation of L-NYS in human plasma for 5 min was 13% +/- 2% in the LDL fraction, 44% +/- 5% in the HDL fraction, and 42% +/- 5% in the LPDP fraction. Similar results were observed following 60 and 120 min of incubation. In addition, the liposome structure of L-NYS was quickly lost when mixed with plasma. These findings suggest that rapid disruption of the L-NYS structure upon incubation in human plasma is consistent with its rapid distribution in plasma. The preferential distribution of NYS into the HDL fraction upon incubation of L-NYS may be a function of its phospholipid composition.
Penetration of GS4071, a novel influenza neuraminidase inhibitor, into rat bronchoalveolar lining fluid following oral administration of the prodrug GS4104
Authors: Eisenberg E J , Bidgood A , Cundy K C
Published: October 2018

GS4071 is a novel potent inhibitor of influenza neuraminidase (Ki < 1 nM) with low (< 5%) oral bioavailability in animals. An ethyl ester prodrug of GS4071, GS4104, has exhibited good oral bioavailability in rat, mouse, and dog models and is currently being developed for the treatment of influenza A and B virus infections. Since influenza virus replicates primarily in the surface epithelial cells of the respiratory tract, the ability of the prodrug to deliver GS4071 to the bronchoalveolar lining fluid (BALF) following an oral dose of GS4104 should be an important indicator of its potential efficacy. In the present study, we determined the concentration-time profiles of GS4071 in the BALF and plasma of rats following oral administration of GS4104. The BALF was sampled by bronchoalveolar lavage with endogenous urea as a dilution marker. The concentration of GS4071 in BALF reached a peak at 2 h (1 h after the plasma peak) and declined at a slower rate than plasma levels, suggesting slow clearance of drug from the lung acini. The ratios of the area-under-the-curve (AUC) values of GS4071 in BALF to those in plasma were 1.05 for AUC from 0 to 6 h (AUC(0-6)) and 1.51 for AUC(0-infinity), indicating significant penetration of the parent drug into the lower respiratory tracts of rats following oral administration of the prodrug. No unchanged GS4104 was detected in BALF.
A novel class C beta-lactamase (FOX-2) in Escherichia coli conferring resistance to cephamycins
Authors: Bauernfeind A , Wagner S , Jungwirth R , Schneider I , Meyer D
Published: October 2018

An Escherichia coli strain resistant to a broad spectrum of beta-lactams, including cephamycins, was isolated from a patient suffering from urinary tract infection. A resistance plasmid (pMVP-7) was transferred from the clinical isolate to an Escherichia coli recipient. Both strains produce a cefoxitin-hydrolyzing beta-lactamase focusing at pI 6.7. The phenotype was similar to that of a Klebsiella pneumoniae strain producing cephamycinase FOX-1, so primers were selected from the FOX-1 sequence to amplify the bla gene of the transconjugant. The PCR product obtained was sequenced. The percentage of identity of the deduced amino acid sequence with sequences of other AmpC-type beta-lactamases was 96.9% with FOX-1, 74.9% with CMY-1, and 67.7% with MOX-1. This new plasmid-mediated enzyme is most closely related to FOX-1 (11 amino acid exchanges). We therefore propose the designation FOX-2.
Cytotoxic analogs of the iron(III) chelator pyridoxal isonicotinoyl hydrazone: effects of complexation with copper(II), gallium(III), and iron (III) on their antiproliferative activities
Authors: Richardson D R
Published: October 2018

This study examined if complexation with metals increased the antiproliferative activities of chelators of the pyridoxal isonicotinoyl hydrazone (PIH) class. Addition of iron(III) to some PIH analogs markedly depressed their activities, whereas it had little effect on others. The gallium(III) complex of PIH, but not its copper(II) complex, was more efficient than the apochelator at inhibiting [3H]thymidine incorporation.
Randomized Comparison of Artemether-Benflumetol and Artesunate-Mefloquine in Treatment of MultidrugResistant Falciparum Malaria
Authors: van Vugt M. , Brockman A. , Gemperli B. , Luxemburger C. , Gathmann I. , Royce C. , Slight Thra , Looareesuwan S. , White N. J. , Nosten F.
Published: October 2018

An open, randomized comparison of artemether-benflumetol (CGP 56 697; Novartis) with artesunate-mefloquine was conducted in 617 patients with acute uncomplicated multidrug-resistant falciparum malaria on the western border of Thailand. Both treatments rapidly and reliably cleared fever and parasitemia, and there was no significant difference in the initial therapeutic response parameters. Parasite genotyping was used to distinguish recrudescences from new infections. The 63-day cure rate for artesunate-mefloquine (94%) was significantly higher than the cure rate for artemether-benflumetol (81%) (
P
< 0.001). Both regimens were well tolerated. Nausea, vomiting, dizziness, sleep disorders, and other neurological side effects were between two and four times more common in the artesunate-mefloquine group than in the artemether-benflumetol group (
P
< 0.001). Artemether-benflumetol is effective and very well tolerated in the treatment of multidrug-resistant falciparum malaria. A higher dose than that used in the present study may improve efficacy.
Topoisomerase Mutations in Fluoroquinolone-Resistant and Methicillin-Susceptible and -Resistant Clinical Isolates of
Staphylococcus aureus
Authors: Kaatz Glenn W. , Seo Susan M.
Published: October 2018

The incidence of the various mutations in the genes encoding topoisomerase IV and DNA gyrase in fluoroquinolone-resistant clinical isolates of
Staphylococcus aureus
is not known. Using restriction fragment length polymorphism analysis and DNA sequencing, we found that in fluoroquinolone- and methicillin-resistant strains, mutations in
grlA
and
gyrA
are quite likely to be present together. For fluoroquinolone-resistant but methicillin-susceptible strains, mutations in
grlA
alone are more common.
Efficacy of CS-834 against Experimental Pneumonia Caused by Penicillin-Susceptible and -Resistant
Streptococcus pneumoniae
in Mice
Authors: Fukuoka Takashi , Kawada Harumi , Kitayama Akiko , Koga Tetsufumi , Kubota Mikie , Harasaki Tamako , Kamai Yasuki , Ohya Satoshi , Yasuda Hiroshi , Iwata Masayuki , Kuwahara Shogo
Published: October 2018

The efficacy of CS-834, a novel oral carbapenem, was assessed by using a murine model of pneumonia caused by penicillin-susceptible and penicillin-resistant
Streptococcus pneumoniae
and was compared with those of oral cephems, i.e., cefteram pivoxil, cefpodoxime proxetil, cefdinir, and cefditoren pivoxil. Intranasal inoculation of 10
6
CFU of penicillin-susceptible or penicillin-resistant
S. pneumoniae
in the exponential growth phase induced pneumonia and bacteremia in ddY mice within 48 h. For the treatment of infections caused by the penicillin-susceptible strain the antibiotics were administered orally at 0.4, 2, and 10 mg/kg of body weight twice daily for 2 days beginning at 24 h after bacterial inoculation, and for the treatment of infections caused by a penicillin-resistant strain the antibiotics were administered at 2, 10, and 50 mg/kg twice daily for 2 days beginning at 24 h after bacterial inoculation. Among the antibiotics tested, CS-834 exhibited the most potent efficacy against both types of strains. Against infections caused by penicillin-susceptible
S. pneumoniae
, CS-834 at all doses significantly reduced the numbers of viable cells in both the lungs and blood. Cefpodoxime proxetil at all doses and cefteram pivoxil and cefditoren pivoxil at doses of 2 and 10 mg/kg showed comparable efficacies. Against infections caused by penicillin-resistant
S. pneumoniae
, CS-834 at doses of 10 and 50 mg/kg showed the most potent efficacy among the antibiotics tested, resulting in the maximum decrease in the numbers of viable cells in the lungs. Comparable efficacies were observed with cefteram pivoxil and cefpodoxime proxetil at doses of 50 mg/kg each. The concentration of CS-834 in the lungs and blood was higher than that of cefdinir and was lower than those of the other antibiotics tested, suggesting that the potent therapeutic efficacy of CS-834 reflects its strong activity against
S. pneumoniae.
Host Mutations (
miaA
and
rpsL
) Reduce Tetracycline Resistance Mediated by Tet(O) and Tet(M)
Authors: Taylor Diane E. , Trieber Catharine A. , Trescher Gudrun , Bekkering Michelle
Published: October 2018

The effects of mutations in host genes on tetracycline resistance mediated by the Tet(O) and Tet(M) ribosomal protection proteins, which originated in
Campylobacter
spp. and
Streptococcus
spp., respectively, were investigated by using mutants of
Salmonella typhimurium
and
Escherichia coli
. The
miaA
,
miaB
, and
miaAB
double mutants of
S. typhimurium
specify enzymes for tRNA modification at the adenosine at position 37, adjacent to the anticodon in tRNA. In
S. typhimurium
, this involves biosynthesis of
N
6
-(4-hydroxyisopentenyl)-2-methylthioadenosine (ms
2
io
6
A). The
miaA
mutation reduced the level of tetracycline resistance mediated by both Tet(O) and Tet(M), but the latter showed a greater effect, which was ascribed to the isopentenyl (i
6
) group or to a combination of the methylthioadenosine (ms
2
) and i
6
groups but not to the ms
2
group alone (specified by
miaB
). In addition, mutations in
E. coli rpsL
genes, generating both streptomycin-resistant and streptomycin-dependent strains, were also shown to reduce the level of tetracycline resistance mediated by Tet(O) and Tet(M). The single-site amino acid substitutions present in the
rpsL
mutations were pleiotropic in their effects on tetracycline MICs. These mutants affect translational accuracy and kinetics and suggest that Tet(O) and Tet(M) binding to the ribosome may be reduced or slowed in the
E. coli rpsL
mutants in which the S12 protein is altered. Data from both the
miaA
and
rpsL
mutant studies indicate a possible link between stability of the aminoacyl-tRNA in the ribosomal acceptor site and tetracycline resistance mediated by the ribosomal protection proteins.
Expression of
Pseudomonas aeruginosa
Multidrug Efflux Pumps MexA-MexB-OprM and MexC-MexD-OprJ in a Multidrug-Sensitive
Escherichia coli
Strain
Authors: Srikumar Ramakrishnan , Kon Tatiana , Gotoh Naomasa , Poole Keith
Published: October 2018

The
mexCD-oprJ
and
mexAB-oprM
operons encode components of two distinct multidrug efflux pumps in
Pseudomonas aeruginosa
. To assess the contribution of individual components to antibiotic resistance and substrate specificity, these operons and their component genes were cloned and expressed in
Escherichia coli
. Western immunoblotting confirmed expression of the
P. aeruginosa
efflux pump components in
E. coli
strains expressing and deficient in the endogenous multidrug efflux system (AcrAB), although only the Δ
acrAB
strain, KZM120, demonstrated increased resistance to antibiotics in the presence of the
P. aeruginosa
efflux genes.
E. coli
KZM120 expressing MexAB-OprM showed increased resistance to quinolones, chloramphenicol, erythromycin, azithromycin, sodium dodecyl sulfate (SDS), crystal violet, novobiocin, and, significantly, several β-lactams, which is reminiscent of the operation of this pump in
P. aeruginosa
. This confirmed previous suggestions that MexAB-OprM provides a direct contribution to β-lactam resistance via the efflux of this group of antibiotics. An increase in antibiotic resistance, however, was not observed when MexAB or OprM alone was expressed in KZM120. Thus, despite the fact that β-lactams act within the periplasm, OprM alone is insufficient to provide resistance to these agents.
E. coli
KZM120 expressing MexCD-OprJ also showed increased resistance to quinolones, chloramphenicol, macrolides, SDS, and crystal violet, though not to most β-lactams or novobiocin, again somewhat reminiscent of the antibiotic resistance profile of MexCD-OprJ-expressing strains of
P. aeruginosa
. Surprisingly,
E. coli
KZM120 expressing MexCD alone also showed an increase in resistance to these agents, while an OprJ-expressing KZM120 failed to demonstrate any increase in antibiotic resistance. MexCD-mediated resistance, however, was absent in a
tolC
mutant of KZM120, indicating that MexCD functions in KZM120 in conjunction with TolC, the previously identified outer membrane component of the AcrAB-TolC efflux system. These data confirm that a tripartite efflux pump is necessary for the efflux of all substrate antibiotics and that the
P. aeruginosa
multidrug efflux pumps are functional and retain their substrate specificity in
E. coli.
Activity of Trovafloxacin (with or without Ampicillin-Sulbactam) against Enterococci in an In Vitro Dynamic Model of Infection
Authors: Zinner Stephen H. , Gilbert Deborah , Dudley Michael N.
Published: October 2018

Antibiotic-resistant enterococci are being increasingly identified as causal agents of infection. Trovafloxacin is a new fluoronaphthyridone with enhanced activity against gram-positive cocci and variable activity reported against
Enterococcus
spp. Twenty-one strains of vancomycin-resistant
Enterococcus faecium
and two strains of
Enterococcus faecalis
(one vancomycin resistant) were studied at an initial inoculum of 10
6
CFU/ml in time-kill assays with trovafloxacin (3 mg/liter), ampicillin-sulbactam (100/50 mg/liter), and the combination. Six strains of
E. faecium
(five vancomycin resistant) also were studied in an in vitro two-compartment dynamic model that mimics human pharmacokinetics with trovafloxacin simulated at 300 mg every 12 h (q12h), ampicillin-sulbactam at 2/1 g q6h, and the combination. Peripheral compartments were sampled q2h for 30 h for bacterial counts. Trovafloxacin MICs ranged from 0.5 to 32 mg/liter, and the nine strains of vancomycin-resistant
E. faecium
for which MICs were ≤2 mg/liter were more likely to show a reduction of 2 log units or more in viable counts in time-kill assays than were strains for which MICs were higher. Synergism with ampicillin-sulbactam was found for only one strain (trovafloxacin MIC, 16 mg/liter). Similar results were obtained in the pharmacokinetic model, with 2- to 4-log-unit reductions in viable bacteria for trovafloxacin-susceptible strains. Although no convincing evidence of synergism was found, ampicillin-sulbactam in combination minimized late bacterial regrowth of two trovafloxacin-susceptible strains. These data suggest that this high dose of trovafloxacin (with or without ampicillin-sulbactam) might be useful against strains of vancomycin-resistant
E. faecium
for which MICs were ≤2 mg/liter.
Characterization of Mutations Contributing to Sulfathiazole Resistance in
Escherichia coli
Authors: Vedantam Gayatri , Guay Gordon G. , Austria Natasha E. , Doktor Stella Z. , Nichols Brian P.
Published: October 2018

A sulfathiazole-resistant dihydropteroate synthase (DHPS) present in two different laboratory strains of
Escherichia coli
repeatedly selected for sulfathiazole resistance was mapped to
folP
by P1 transduction. The
folP
mutation in each of the strains was shown to be identical by nucleotide sequence analysis. A single C→T transition resulted in a Pro→Ser substitution at amino acid position 64. Replacement of the mutant
folP
alleles with wild-type
folP
significantly reduced the level of resistance to sulfathiazole but did not abolish it, indicating the presence of an additional mutation(s) that contributes to sulfathiazole resistance in the two strains. Transfer of the mutant
folP
allele to a wild-type background resulted in a strain with only a low level of resistance to sulfathiazole, suggesting that the presence of the resistant DHPS was not in itself sufficient to account for the overall sulfathiazole resistance in these strains of
E. coli
. Additional characterization of an amplified secondary resistance determinant,
sur
, present in one of the strains, identified it as the previously identified bicyclomycin resistance determinant
bcr
, a member of a family of membrane-bound multidrug resistance antiporters. An additional mutation contributing to sulfathiazole resistance,
sux
, has also been identified and has been shown to affect the histidine response to adenine sensitivity displayed by these
purU
strains.