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ABSTRACT: Background: Pseudomonas aeruginosa pneumonia remains a difficult therapeutic problem. Optimal doses and modes of administration of single agents often do not result in acceptable outcomes. Further, emergence of resistance occurs frequently in this setting with single agent chemotherapy. The purpose of these experiments was to evaluate combination chemotherapy with meropenem plus tobramycin for P. aeruginosa in a murine pneumonia model.Methods: We employed a murine pneumonia model. Neutropenia was induced by cyclophosphamide. Pharmacokinetics of meropenem and tobramycin were determined using a population pharmacokinetic approach. Both drugs were given 4-hourly. Meropenem was administered as total daily doses of 30-600 mg/kg while tobramycin ranged from 50-400 mg/kg. Combination therapy evaluated all combinations of 50, 100 and 150 mg/kg/day of tobramycin with 60 or 300 mg/kg/day of meropenem. Total and drug-resistant organisms were enumerated.Results: Meropenem alone had a near-maximal effect at 60 mg/kg/day, (3.18 log10(CFU/g) kill from stasis). The Time > MIC in ELF at this dose was 35.25% of 24 hrs. For tobramycin alone, near-maximal effect was at 150 mg/kg/day and the AUC/MIC in ELF was 240.3. Resistance suppression occurred at an ELF AUC/MIC ratio of 110.6 For combination therapy, near-maximal effect was reached at 60 mg/kg/day/50 mg/kg/day of meropenem/tobramycin which produced a 35.25% Time>MIC in ELF and an ELF AUC/MIC ratio of 80.1. Interaction was additive. All combination regimens suppressed resistance.Conclusions: Combination therapy produced additive drug interaction and suppressed all resistance amplification. It is likely that optimal therapy for Pseudomonas aeruginosa pneumonia will involve combination of agents.
Antimicrobial Agents and Chemotherapy 04/2013; · 4.84 Impact Factor
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Gary Nieman, David Brown,
Joydeep Sarkar,
Brian Kubiak,
Cordelia Ziraldo,
Joyeeta Dutta-Moscato,
Christopher Vieau,
Derek Barclay,
Louis Gatto,
Kristopher Maier,
Gregory Constantine,
Timothy R Billiar,
Ruben Zamora,
Qi Mi,
Steve Chang,
Yoram Vodovotz
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ABSTRACT: To gain insights into individual variations in acute inflammation and physiology.
Large-animal study combined with mathematical modeling.
Academic large-animal and computational laboratories.
Outbred juvenile swine.
Four swine were instrumented and subjected to endotoxemia (100 µg/kg), followed by serial plasma sampling.
Swine exhibited various degrees of inflammation and acute lung injury, including one death with severe acute lung injury (PaO(2)/FIO(2) ratio μ200 and static compliance μ10 L/cm H(2)O). Plasma interleukin-1β, interleukin-4, interleukin-6, interleukin-8, interleukin-10, tumor necrosis factor-α, high mobility group box-1, and NO(2)/NO(3) were significantly (p μ .05) elevated over the course of the experiment. Principal component analysis was used to suggest principal drivers of inflammation. Based in part on principal component analysis, an ordinary differential equation model was constructed, consisting of the lung and the blood (as a surrogate for the rest of the body), in which endotoxin induces tumor necrosis factor-α in monocytes in the blood, followed by the trafficking of these cells into the lung leading to the release of high mobility group box-1, which in turn stimulates the release of interleukin-1β from resident macrophages. The ordinary differential equation model also included blood pressure, PaO(2), and FIO(2), and a damage variable that summarizes the health of the animal. This ordinary differential equation model could be fit to both inflammatory and physiologic data in the individual swine. The predicted time course of damage could be matched to the oxygen index in three of the four swine.
The approach described herein may aid in predicting inflammation and physiologic dysfunction in small cohorts of subjects with diverse phenotypes and outcomes.
Critical care medicine 04/2012; 40(4):1052-63. · 6.37 Impact Factor
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ABSTRACT: Phenoxodiol is an isoflavone derivative that has been shown to elicit cytotoxic effects against a broad range of human cancers. We examined the effect of phenoxodiol on cell death pathways on the prostate cell lines LNCaP, DU145 and PC3, representative of different stages of prostate cancer, and its effects on cell death pathways in these cell lines. Cell proliferation assays demonstrated a significant reduction in the rate of cell proliferation after 48 h exposure to phenoxodiol (10 and 30 μM). FACS analysis and 3'-end labelling indicated that all three prostate cancer cell lines underwent substantial levels of cell death 48 h after treatment. Mitochondrial membrane depolarization, indicative of early-stage cell death signalling, using JC-1 detection, was also apparent in all cell lines after exposure to phenoxodiol in the absence of caspase-3 activation. Caspase inhibition assays indicated that phenoxodiol operates through a caspase-independent cell death pathway. These data demonstrate that phenoxodiol elicits anti-cancer effects in prostate cancer cell lines representative of early and later stages of development through an as-yet-unknown cell death mechanism. These data warrant the further investigation of phenoxodiol as a potential treatment for prostate cancer.
Journal of Biosciences 03/2012; 37(1):73-84. · 1.65 Impact Factor
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ABSTRACT: To evaluate a sample of Internet sites advertising statins for sale to the general public.
A simulated customer search and evaluation of retrieved sites using evaluation tools focussing on quality (Q) and safe medicine use (SMU). Sites retrieved on 17 November 2010 were systematically analysed from 19 November to 23 December 2010.
One hundred eighty-four sites met the inclusion criteria: 40 each for atorvastatin, pravastatin, rosuvastatin, and simvastatin and 24 for fluvastatin. Sites originated from 17 different countries. Most sites scored less than half the maximum Q score (26; range 5-17). Mean total SMU scores for each statin group were lower than 50% of the maximum (45; range of 0-28). There were no statistically significant differences between statins. General contraindications were absent in 92.4% of sites and contraindicated medicines in 47.3%. Key warnings on the appearance of symptoms associated with myopathy, liver disease, hypersensitivity, and pancreatitis were absent in 37, 48.4, 91.3, and 96.2% of sites, respectively. Most websites presented a chaotic and incomplete list of known side effects; just 13 (7.1%) presented a list compatible with current prescribing information. Only two-thirds (65.8%) attempted to describe any in lay language.
A potential purchaser of statins is likely to encounter websites from a wide geographical base and of generally poor quality. This has potentially serious implications for the safety of purchasers who may not be aware of the problems associated with ordering medicines online or the actual medication, which they receive. Direct to consumer advertising websites need tighter controls.
Pharmacoepidemiology and Drug Safety 02/2012; 21(4):352-65. · 2.53 Impact Factor
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G L Drusano,
Robert A Bonomo,
Nadzeya Bahniuk,
Juergen B Bulitta,
Brian Vanscoy,
Holland Defiglio,
Steven Fikes, David Brown,
Sarah M Drawz,
Robert Kulawy,
Arnold Louie
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ABSTRACT: The panoply of resistance mechanisms in Pseudomonas aeruginosa makes resistance suppression difficult. Defining optimal regimens is critical. Cefepime is a cephalosporin whose 3' side chain provides some stability against AmpC β-lactamases. We examined the activity of cefepime against P. aeruginosa wild-type strain PAO1 and its isogenic AmpC stably derepressed mutant in our hollow-fiber infection model. Dose-ranging studies demonstrated complete failure with resistance emergence (both isolates). Inoculum range studies demonstrated ultimate failure for all inocula. Lower inocula failed last (10 days to 2 weeks). Addition of a β-lactamase inhibitor suppressed resistance even with the stably derepressed isolate. Tobramycin combination studies demonstrated resistance suppression in both the wild-type and the stably derepressed isolates. Quantitating the RNA message by quantitative PCR demonstrated that tobramycin decreased the message relative to that in cefepime-alone experiments. Western blotting with AmpC-specific antibody for P. aeruginosa demonstrated decreased expression. We concluded that suppression of β-lactamase expression by tobramycin (a protein synthesis inhibitor) was at least part of the mechanism behind resistance suppression. Monte Carlo simulation demonstrated that a regimen of 2 g of cefepime every 8 h plus 7 mg/kg of body weight of tobramycin daily would provide robust resistance suppression for Pseudomonas isolates with cefepime MIC values up to 8 mg/liter and tobramycin MIC values up to 1 mg/liter. For P. aeruginosa resistance suppression, combination therapy is critical.
Antimicrobial Agents and Chemotherapy 01/2012; 56(1):231-42. · 4.84 Impact Factor
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Arnold Louie,
Mariana Castanheira,
Weiguo Liu,
Caroline Grasso,
Ronald N Jones,
Gregory Williams,
Ian Critchley,
Dirk Thye, David Brown,
Brian Vanscoy,
Robert Kulawy,
G L Drusano
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ABSTRACT: New broad-spectrum β-lactamases such as KPC enzymes and CTX-M-15 enzymes threaten to markedly reduce the utility of our armamentarium of β-lactam agents, even our most potent drugs, such as carbapenems. NXL104 is a broad-spectrum non-β-lactam β-lactamase inhibitor. In this evaluation, we examined organisms carrying defined β-lactamases and identified doses and schedules of NXL104 in combination with the new cephalosporin ceftaroline, which would maintain good bacterial cell kill and suppress resistance emergence for a clinically relevant period of 10 days in our hollow-fiber infection model. We examined three strains of Klebsiella pneumoniae and one isolate of Enterobacter cloacae. K. pneumoniae 27-908M carried KPC-2, SHV-27, and TEM-1 β-lactamases. Its isogenic mutant, K. pneumoniae 4207J, was "cured" of the plasmid expressing the KPC-2 enzyme. K. pneumoniae 24-1318A carried a CTX-M-15 enzyme, and E. cloacae 2-77C expressed a stably derepressed AmpC chromosomal β-lactamase. Dose-ranging experiments for NXL104 administered as a continuous infusion with ceftaroline at 600 mg every 8 h allowed identification of a 24-h area under the concentration-time curve (AUC) for NXL104 that mediated bactericidal activity and resistance suppression. Dose fractionation experiments identified that "time > threshold" was the pharmacodynamic index linked to cell kill and resistance suppression. Given these results, we conclude that NXL104 combined with ceftaroline on an 8-hourly administration schedule would be optimal for circumstances in which highly resistant pathogens are likely to be encountered. This combination dosing regimen should allow for optimal bacterial cell kill (highest likelihood of successful clinical outcome) and the suppression of resistance emergence.
Antimicrobial Agents and Chemotherapy 01/2012; 56(1):258-70. · 4.84 Impact Factor
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ABSTRACT: Non small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality world-wide and the majority of cases are diagnosed at late stages of disease. There is currently no cost-effective screening test for NSCLC, and the development of such a test is a public health imperative. Recent studies have suggested that chest computed tomography screening of patients at high risk of lung cancer can increase survival from disease, however, the cost effectiveness of such screening has not been established. In this Phase I/II biomarker study we examined the feasibility of using serum miRNA as biomarkers of NSCLC using RT-qPCR to examine the expression of 180 miRNAs in sera from 30 treatment naive NSCLC patients and 20 healthy controls. Receiver operating characteristic curves (ROC) and area under the curve were used to identify differentially expressed miRNA pairs that could distinguish NSCLC from healthy controls. Selected miRNA candidates were further validated in sera from an additional 55 NSCLC patients and 75 healthy controls. Examination of miRNA expression levels in serum from a multi-institutional cohort of 50 subjects (30 NSCLC patients and 20 healthy controls) identified differentially expressed miRNAs. A combination of two differentially expressed miRNAs miR-15b and miR-27b, was able to discriminate NSCLC from healthy controls with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100% in the training set. Upon further testing on additional 130 subjects (55 NSCLC and 75 healthy controls), this miRNA pair predicted NSCLC with a specificity of 84% (95% CI 0.73-0.91), sensitivity of 100% (95% CI; 0.93-1.0), NPV of 100%, and PPV of 82%. These data provide evidence that serum miRNAs have the potential to be sensitive, cost-effective biomarkers for the early detection of NSCLC. Further testing in a Phase III biomarker study in is necessary for validation of these results.
PLoS ONE 01/2012; 7(2):e32307. · 4.09 Impact Factor
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PLoS ONE 01/2012; 7(5). · 4.09 Impact Factor
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ABSTRACT: Yersinia pestis, the bacterium that causes plague, is a potential agent of bioterrorism. Streptomycin is the "gold standard" for the treatment of plague infections in humans, but the drug is not available in many countries, and resistance to this antibiotic occurs naturally and has been generated in the laboratory. Other antibiotics have been shown to be active against Y. pestis in vitro and in vivo. However, the relative efficacies of clinically prescribed regimens of these antibiotics with streptomycin and with each other for the killing of Yersinia pestis are unknown. The efficacies of simulated pharmacokinetic profiles for human 10-day clinical regimens of ampicillin, meropenem, moxifloxacin, ciprofloxacin, and gentamicin were compared with the gold standard, streptomycin, for killing of Yersinia pestis in an in vitro pharmacodynamic model. Resistance amplification with therapy was also assessed. Streptomycin killed the microbe in one trial but failed due to resistance amplification in the second trial. In two trials, the other antibiotics consistently reduced the bacterial densities within the pharmacodynamic systems from 10⁸ CFU/ml to undetectable levels (<10² CFU/ml) between 1 and 3 days of treatment. None of the comparator agents selected for resistance. The comparator antibiotics were superior to streptomycin against Y. pestis and deserve further evaluation.
Antimicrobial Agents and Chemotherapy 06/2011; 55(6):2623-8. · 4.84 Impact Factor
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Hung-Yun Lin,
Cornelia B Landersdorfer,
David London,
Ran Meng,
Chang-Uk Lim,
Cassie Lin,
Sharon Lin,
Heng-Yuan Tang, David Brown,
Brian Van Scoy,
Robert Kulawy,
Lurdes Queimado,
George L Drusano,
Arnold Louie,
Faith B Davis,
Shaker A Mousa,
Paul J Davis
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ABSTRACT: Unmodified or as a poly[lactide-co-glycolide] nanoparticle, tetraiodothyroacetic acid (tetrac) acts at the integrin αvβ3 receptor on human cancer cells to inhibit tumor cell proliferation and xenograft growth. To study in vitro the pharmacodynamics of tetrac formulations in the absence of and in conjunction with other chemotherapeutic agents, we developed a perfusion bellows cell culture system. Cells were grown on polymer flakes and exposed to various concentrations of tetrac, nano-tetrac, resveratrol, cetuximab, or a combination for up to 18 days. Cells were harvested and counted every one or two days. Both NONMEM VI and the exact Monte Carlo parametric expectation maximization algorithm in S-ADAPT were utilized for mathematical modeling. Unmodified tetrac inhibited the proliferation of cancer cells and did so with differing potency in different cell lines. The developed mechanism-based model included two effects of tetrac on different parts of the cell cycle which could be distinguished. For human breast cancer cells, modeling suggested a higher sensitivity (lower IC50) to the effect on success rate of replication than the effect on rate of growth, whereas the capacity (Imax) was larger for the effect on growth rate. Nanoparticulate tetrac (nano-tetrac), which does not enter into cells, had a higher potency and a larger anti-proliferative effect than unmodified tetrac. Fluorescence-activated cell sorting analysis of harvested cells revealed tetrac and nano-tetrac induced concentration-dependent apoptosis that was correlated with expression of pro-apoptotic proteins, such as p53, p21, PIG3 and BAD for nano-tetrac, while unmodified tetrac showed a different profile. Approximately additive anti-proliferative effects were found for the combinations of tetrac and resveratrol, tetrac and cetuximab (Erbitux), and nano-tetrac and cetuximab. Our in vitro perfusion cancer cell system together with mathematical modeling successfully described the anti-proliferative effects over time of tetrac and nano-tetrac and may be useful for dose-finding and studying the pharmacodynamics of other chemotherapeutic agents or their combinations.
PLoS Computational Biology 01/2011; 7(2):e1001073. · 5.22 Impact Factor
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Arnold Louie,
Adam Bied,
Christine Fregeau,
Brian Van Scoy, David Brown,
Weiguo Liu,
Karen Bush,
Anne-Marie Queenan,
Brian Morrow,
Mohammed Khashab,
James B Kahn,
Susan Nicholson,
Robert Kulawy,
G L Drusano
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ABSTRACT: We compared drugs (imipenem and doripenem), doses (500 mg and 1 g), and infusion times (0.5 and 1.0 [imipenem], 1.0 and 4.0 h [doripenem]) in our hollow-fiber model, examining cell kill and resistance suppression for three isogenic strains of Pseudomonas aeruginosa PAO1. The experiments ran for 10 days. Serial samples were taken for total organism and resistant subpopulation counts. Drug concentrations were determined by high-pressure liquid chromatography-tandem mass spectrometry (LC/MS/MS). Free time above the MIC (time > MIC) was calculated using ADAPT II. Time to resistance emergence was examined with Cox modeling. Cell kill and resistance emergence differences were explained, in the main, by differences in potency (MIC) between doripenem and imipenem. Prolonged infusion increased free drug time > MIC and improved cell kill. For resistance suppression, the 1-g, 4-h infusion was able to completely suppress resistance for the full period of observation for the wild-type isolate. For the mutants, control was ultimately lost, but in all cases, this was the best regimen. Doripenem gave longer free time > MIC than imipenem and, therefore, better cell kill and resistance suppression. For the wild-type organism, the 1-g, 4-h infusion regimen is preferred. For organisms with resistance mutations, larger doses or addition of a second drug should be studied.
Antimicrobial Agents and Chemotherapy 03/2010; 54(6):2638-45. · 4.84 Impact Factor
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ABSTRACT: Isoniazid, administered as part of combination antituberculosis therapy, is responsible for most of the early bactericidal activity (EBA) of the regimen. However, the emergence of Mycobacterium tuberculosis resistance to isoniazid is a major problem. We examined the relationship between isoniazid exposure and M. tuberculosis microbial kill, as well as the emergence of resistance, in our in vitro pharmacodynamic model of tuberculosis. Since single-nucleotide polymorphisms of the N-acetyltransferase-2 gene lead to two different clearances of isoniazid from serum in patients, we simulated the isoniazid concentration-time profiles encountered in both slow and fast acetylators. Both microbial kill and the emergence of resistance during monotherapy were associated with the ratio of the area under the isoniazid concentration-time curve from 0 to 24 h (AUC(0-24)) to the isoniazid MIC. The time in mutant selection window hypothesis was rejected. Next, we utilized the in vitro relationship between the isoniazid AUC(0-24)/MIC ratio and microbial kill, the distributions of isoniazid clearance in populations with different percentages of slow and fast acetylators, and the distribution of isoniazid MICs for isonazid-susceptible M. tuberculosis clinical isolates in Monte Carlo simulations to calculate the EBA expected for approximately 10,000 patients treated with 300 mg of isoniazid. For those patient populations in which the proportion of fast acetylators and the isoniazid MICs were high, the average EBA of the standard dose was approximately 0.3 log(10) CFU/ml/day and was thus suboptimal. Our approach, which utilizes preclinical pharmacodynamics and the genetically determined multimodal distributions of serum clearances, is a preclinical tool that may be able to predict the EBAs of various doses of new antituberculosis drugs.
Antimicrobial Agents and Chemotherapy 08/2007; 51(7):2329-36. · 4.84 Impact Factor
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ABSTRACT: It is believed that the cessation of isoniazid's early bactericidal activity during the initial phase of antituberculosis therapy is due to the depletion of Mycobacterium tuberculosis in the exponential phase of growth. We examined the veracity of this cornerstone belief.
We used an in vitro infection model in which M. tuberculosis was exposed to isoniazid concentration-time profiles encountered in human patients. Experiments were performed to examine the time-related changes in the total bacterial population, the isoniazid-susceptible subpopulation, and the isoniazid-resistant subpopulation.
The cessation of microbial kill occurred between days 3 and 4 of isoniazid therapy, as occurs in patients. There were multiple logs of organisms in the exponential phase of growth remaining at the time when bactericidal activity ceased. The isoniazid-susceptible subpopulation was replaced by an isoniazid-resistant subpopulation after 80 h of therapy. The size of the isoniazid-susceptible subpopulation continued to decrease after the total population had ceased to decrease, whereas the resistant subpopulation remained in the exponential phase of growth. Resistance was due to single point mutations in the catalase-peroxidase gene and to reserpine-inhibitable efflux pumps.
The age-old hypothesis that isoniazid's microbial killing of M. tuberculosis during log-phase growth ceases because of the depletion of this bacillary population needs to be modified.
The Journal of Infectious Diseases 02/2007; 195(2):194-201. · 6.41 Impact Factor
