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1.  In Vitro and In Vivo Evaluation of 28DAP010, a Novel Diamidine for Treatment of Second-Stage African Sleeping Sickness 
African sleeping sickness is a neglected tropical disease transmitted by tsetse flies. New and better drugs are still needed especially for its second stage, which is fatal if untreated. 28DAP010, a dipyridylbenzene analogue of DB829, is the second simple diamidine found to cure mice with central nervous system infections by a parenteral route of administration. 28DAP010 showed efficacy similar to that of DB829 in dose-response studies in mouse models of first- and second-stage African sleeping sickness. The in vitro time to kill, determined by microcalorimetry, and the parasite clearance time in mice were shorter for 28DAP010 than for DB829. No cross-resistance was observed between 28DAP010 and pentamidine on the tested Trypanosoma brucei gambiense isolates from melarsoprol-refractory patients. 28DAP010 is the second promising preclinical candidate among the diamidines for the treatment of second-stage African sleeping sickness.
doi:10.1128/AAC.02309-13
PMCID: PMC4136055  PMID: 24867978
2.  Plasma Concentrations of Isoniazid and Rifampin Are Decreased in Adult Pulmonary Tuberculosis Patients with Diabetes Mellitus 
Antimicrobial Agents and Chemotherapy  2013;57(11):5740-5742.
Plasma isoniazid and rifampin concentrations, but not pyrazinamide and ethambutol concentrations, were decreased by about 50% (P < 0.05) in diabetic pulmonary tuberculosis patients. The prevalences of subnormal plasma isoniazid, rifampin, pyrazinamide, and ethambutol concentrations were 49% or 100% (P < 0.01), 66% or 100% (P < 0.05), 30% or 50% (P = 0.198), and 32% or 21% (P = 0.742) in nondiabetic or diabetic tuberculosis patients, respectively. These data show that plasma concentrations of isoniazid and rifampin were greatly reduced in diabetic tuberculosis patients.
doi:10.1128/AAC.01345-13
PMCID: PMC3811326  PMID: 23979746
3.  Green Fluorescent Diamidines as Diagnostic Probes for Trypanosomes 
Light-emitting diode (LED) fluorescence microscopy offers potential benefits in the diagnosis of human African trypanosomiasis and in other aspects of diseases management, such as detection of drug-resistant strains. To advance such approaches, reliable and specific fluorescent markers to stain parasites in human fluids are needed. Here we describe a series of novel green fluorescent diamidines and their suitability as probes with which to stain trypanosomes.
doi:10.1128/AAC.02024-13
PMCID: PMC3957857  PMID: 24366732
4.  The Trypanocidal Activity of Amidine Compounds Does Not Correlate with Their Binding Affinity to Trypanosoma cruzi Kinetoplast DNA▿ 
Antimicrobial Agents and Chemotherapy  2011;55(10):4765-4773.
Due to limited efficacy and considerable toxicity, the therapy for Chagas' disease is far from being ideal, and thus new compounds are desirable. Diamidines and related compounds such as arylimidamides have promising trypanocidal activity against Trypanosoma cruzi. To better understand the mechanism of action of these heterocyclic cations, we investigated the kinetoplast DNA (kDNA) binding properties and trypanocidal efficacy against T. cruzi of 13 compounds. Four diamidines (DB75, DB569, DB1345, and DB829), eight arylimidamides (DB766, DB749, DB889, DB709, DB613, DB1831, DB1852, and DB2002), and one guanylhydrazone (DB1080) were assayed in thermal denaturation (Tm) and circular dichroism (CD) studies using whole purified T. cruzi kDNA and a conserved synthetic parasite sequence. The overall CD spectra using the whole kDNA were similar to those found for the conserved sequence and were indicative of minor groove binding. Our findings showed that some of the compounds that exhibited the highest trypanocidal activities (e.g., DB766) caused low or no change in the Tm measurements. However, while some active compounds, such as DB766, induced profound alterations of kDNA topology, others, like DB1831, although effective, did not result in altered Tm and CD measurements. Our data suggest that the strong affinity of amidines with kDNA per se is not sufficient to generate and trigger their trypanocidal activity. Cell uptake differences and possibly distinct cellular targets need to be considered in the final evaluation of the mechanisms of action of these compounds.
doi:10.1128/AAC.00229-11
PMCID: PMC3186963  PMID: 21807972
5.  Efficacy and Safety of Nemonoxacin versus Levofloxacin for Community-Acquired Pneumonia▿  
Antimicrobial Agents and Chemotherapy  2010;54(10):4098-4106.
Nemonoxacin, a novel nonfluorinated quinolone, exhibits potent in vitro and in vivo activities against community-acquired pneumonia (CAP) pathogens, including multidrug-resistant Streptococcus pneumoniae. Patients with mild to moderate CAP (n = 265) were randomized to receive oral nemonoxacin (750 mg or 500 mg) or levofloxacin (500 mg) once daily for 7 days. Clinical responses were determined at the test-of-cure visit in intent-to-treat (ITT), clinical per protocol (PPc), evaluable-ITT, and evaluable-PPc populations. The clinical cure rates for 750 mg nemonoxacin, 500 mg nemonoxacin, and levofloxacin were 89.9%, 87.0%, and 91.1%, respectively, in the evaluable-ITT population; 91.7%, 87.7%, and 90.3%, respectively, in the evaluable-PPc population; 82.6%, 75.3%, and 80.0%, respectively, in the ITT population; and 83.5%, 78.0%, and 82.3%, respectively, in the PPc population. Noninferiority to levofloxacin was demonstrated in both the 750-mg and 500-mg nemonoxacin groups for the evaluable-ITT and evaluable-PPc populations, and also in the 750 mg nemonoxacin group for the ITT and PPc populations. Overall bacteriological success rates were high for all treatment groups in the evaluable-bacteriological ITT population (90.2% in the 750 mg nemonoxacin group, 84.8% in the 500 mg nemonoxacin group, and 92.0% in the levofloxacin group). All three treatments were well tolerated, and no drug-related serious adverse events were observed. Overall, oral nemonoxacin (both 750 mg and 500 mg) administered for 7 days resulted in high clinical and bacteriological success rates in CAP patients. Further, good tolerability and excellent activity against common causative pathogens were demonstrated. Nemonoxacin (750 mg and 500 mg) once daily is as effective and safe as levofloxacin (500 mg) once daily for the treatment of CAP.
doi:10.1128/AAC.00295-10
PMCID: PMC2944601  PMID: 20660689
6.  Paradoxical Growth of Candida dubliniensis Does Not Preclude In Vivo Response to Echinocandin Therapy ▿  
Antimicrobial Agents and Chemotherapy  2009;53(12):5297-5299.
Candida dubliniensis commonly shows paradoxical or trailing growth effects in vitro in the presence of echinocandins. We tested the in vitro activities of anidulafungin, caspofungin, and micafungin against clinical isolates of C. dubliniensis and evaluated the efficacy of these drugs in two murine models of systemic infection. The three echinocandins were similarly effective in the treatment of experimental disseminated infections with C. dubliniensis strains showing or not showing abnormal growth in vitro.
doi:10.1128/AAC.00980-09
PMCID: PMC2786325  PMID: 19786599
7.  New Treatment Option for Second-Stage African Sleeping Sickness: In Vitro and In Vivo Efficacy of Aza Analogs of DB289 ▿  
Antimicrobial Agents and Chemotherapy  2009;53(10):4185-4192.
African sleeping sickness is a fatal parasitic disease, and all drugs currently in use for treatment have strong liabilities. It is essential to find new, effective, and less toxic drugs, ideally with oral application, to control the disease. In this study, the aromatic diamidine DB75 (furamidine) and two aza analogs, DB820 and DB829 (CPD-0801), as well as their methoxyamidine prodrugs and amidoxime metabolites, were evaluated against African trypanosomes. The active parent diamidines showed similar in vitro profiles against different Trypanosoma brucei strains, melarsoprol- and pentamidine-resistant lines, and a P2 transporter knockout strain (AT1KO), with DB75 as the most trypanocidal molecule. In the T. b. rhodesiense strain STIB900 acute mouse model, the aza analogs DB820 and DB829 demonstrated activities superior to that of DB75. The aza prodrugs DB844 and DB868, as well as two metabolites of DB844, were orally more potent in the T. b. brucei strain GVR35 mouse central nervous system (CNS) model than DB289 (pafuramidine maleate). Unexpectedly, the parent diamidine DB829 showed high activity in the mouse CNS model by the intraperitoneal route. In conclusion, DB868 with oral and DB829 with parenteral application are potential candidates for further development of a second-stage African sleeping sickness drug.
doi:10.1128/AAC.00225-09
PMCID: PMC2764217  PMID: 19620327
8.  Diphenyl Furans and Aza Analogs: Effects of Structural Modification on In Vitro Activity, DNA Binding, and Accumulation and Distribution in Trypanosomes▿  
Human African trypanosomiasis is a devastating disease with only a few treatment options, including pentamidine. Diamidine compounds such as pentamidine, DB75, and DB820 are potent antitrypanosomal compounds. Previous investigations have shown that diamidines accumulate to high concentrations in trypanosomes. However, the mechanism of action of this class of compounds remains unknown. A long-hypothesized mechanism of action has been binding to DNA and interference with DNA-associated enzymes. The fluorescent diamidines, DB75 and DB820, have been shown to localize not only in the DNA-containing nucleus and kinetoplast of trypanosomes but also to the acidocalcisomes. Here we investigate two series of analogs of DB75 and DB820 with various levels of in vitro antitrypanosomal activity to determine whether any correlation exists between trypanosome accumulation, distribution, and in vitro activity. Despite wide ranges of in vitro antitrypanosomal activity, all of the compounds investigated accumulated to millimolar concentrations in trypanosomes over a period of 8 h. Interestingly, some of the less potent compounds accumulated to concentrations much higher than those of more potent compounds. All of the compounds were localized to the DNA-containing nucleus and/or kinetoplast, and many were also found in the acidocalcisomes. Accumulation in the nucleus and kinetoplast should be important to the mechanism of action of these compounds. The acidocalcisomes may also play a role in the mechanism of action of these compounds. This investigation suggests that the extent of accumulation alone is not responsible for killing trypanosomes and that organelle-specific accumulation may not predict in vitro activity.
doi:10.1128/AAC.00005-07
PMCID: PMC1932548  PMID: 17517831
9.  Accumulation and Intracellular Distribution of Antitrypanosomal Diamidine Compounds DB75 and DB820 in African Trypanosomes 
The aromatic diamidine pentamidine has long been used to treat early-stage human African trypanosomiasis (HAT). Two analogs of pentamidine, DB75 and DB820, have been shown to be more potent and less toxic than pentamidine in murine models of trypanosomiasis. The diphenyl furan diamidine, DB75, is the active metabolite of the prodrug DB289, which is currently in phase III clinical trials as a new orally active candidate drug to treat first-stage HAT. The new aza analog, DB820, is the active diamidine of the prodrug DB844, currently undergoing preclinical evaluation as a new candidate to treat HAT of the central nervous system. The exact mechanisms of antitrypanosomal activity of aromatic dications remain poorly understood, with multiple mechanisms hypothesized. Pentamidine is known to be actively transported into trypanosomes and binds to DNA within the nucleus and kinetoplast. A long-hypothesized mechanism of action has been that DNA binding ultimately leads to interference with DNA-associated enzymes. Both DB75 and DB820 are intensely fluorescent, which provides an important tool for determining the kinetics of accumulation and intracellular distribution in trypanosomes. We show in the current study that DB75 and DB820 rapidly accumulate and strongly concentrate within trypanosomes, with intracellular concentrations over 15,000-fold higher than mouse plasma concentrations. Both compounds initially accumulate in the DNA-containing nucleus and kinetoplast, but at later time points, they concentrate in non-DNA-containing cytoplasmic organelles. Analyses of the kinetics of uptake and intracellular distribution are necessary to begin to define antitrypanosomal mechanisms of action of DB75, DB820, and other aromatic diamidines.
doi:10.1128/AAC.00192-06
PMCID: PMC1479144  PMID: 16723581
10.  The Action of Bismuth against Helicobacter pylori Mimics but Is Not Caused by Intracellular Iron Deprivation 
Helicobacter pylori is highly susceptible to bismuth, a heavy metal with antimicrobial activity linked to its effect on bacterial iron uptake. Three strains of H. pylori were analyzed for indicators of iron limitation following exposure to the MIC of colloidal bismuth subcitrate (MICCBS). Similar morphologic and outer membrane changes were observed following growth in iron-limiting medium and at the MICCBS that inhibited the growth of all three strains. These changes, which were also observed for iron-limited bacteria, were alleviated by the addition of iron to the cultures. H. pylori ATP levels, reduced in iron-limiting medium, were below the limits of detection in two of the three strains following exposure to bismuth. The addition of iron partially restored bacterial ATP levels in these two strains, although not to normal concentrations. In contrast, exposure of the same strains to the MICCBS failed to deplete intracellular levels of iron, which were significantly reduced by culturing in iron-limiting medium. Thus, the antimicrobial effect of bismuth and of iron limitation on H. pylori may be similar. However, the respective mechanisms of intracellular action would appear to be mediated by different pathways within the cell.
doi:10.1128/AAC.48.6.1983-1988.2004
PMCID: PMC415606  PMID: 15155188
12.  Lack of evidence for a saturable tetracycline transport system in Staphylococcus aureus. 
Antimicrobial Agents and Chemotherapy  1991;35(12):2643-2644.
Previous studies on tetracycline transport into Staphylococcus aureus identified a high-affinity, saturable uptake system for the antibiotic (Km, 4.76 microM) (B.L. Hutchings, Biochim. Biophys. Acta 174:734-738, 1969). However, the earlier results could not be confirmed using conditions that permitted energy-dependent, concentrative uptake of tetracycline. Kinetic artifacts introduced by inappropriate washing procedures may explain the previous results.
PMCID: PMC245447  PMID: 1810200

Results 1-12 (12)