´veloppement, Dakar, Senegal Abstract. The in vitro activities of doxycycline, chloroquine, quini... more ´veloppement, Dakar, Senegal Abstract. The in vitro activities of doxycycline, chloroquine, quinine, amodiaquine, artemether, pyrimethamine, and cycloguanil were evaluated against Plasmodium falciparumisolates from Senegal (Dielmo and Ndiop), using an isotopic, micro, drug susceptibility test. The 71 50% inhibitory concentration (IC 50) values for doxycycline ranged from 0.7 to 108.0 M and the geometric mean IC50 for the 71 isolates was
The effectsof combining four dihydroethanoanthracenic (DEA) derivativ esand chloroquine were as -... more The effectsof combining four dihydroethanoanthracenic (DEA) derivativ esand chloroquine were as - sessed in vitro against Plasmodium falciparum chloroquine resistant parasites W2, Palo Alto, FCR3, and Bres1. Like verapamil or promethazine, the four dihydroethanoanthracenic derivatives tested can be added to the growing list of agentsthat s how capability in enhancing the activity of chloroquine agai nst resistant parasites. The structurally
Our objective was to evaluate the efficacy of fipronil for the prevention of Ehrlichia canis tran... more Our objective was to evaluate the efficacy of fipronil for the prevention of Ehrlichia canis transmission to dogs by Rhipicephalus sanguineus in two endemic areas situated in Africa (Dakar and Djibouti). We carried out controlled trials in kennels for 1 year on 248 dogs, mainly police dogs and military working dogs. Eight groups were studied in a multi-centre study. Fifty
Canine monocytic ehrlichiosis is an infectious worldwide disease caused by small obligatory intra... more Canine monocytic ehrlichiosis is an infectious worldwide disease caused by small obligatory intramonocytic bacterium (Ehrlichia canis) transmitted by ticks (Rhipicephalus sanguineus). The infection is characterized by non specific clinical signs (hyperthermia, anorexia…) which can only orient the veterinary practician towards a presumptive diagnosis. The main biological signs associated with canine ehrlichiosis are thrombocytopenia, leucopenia or leucocytosis, anemia, rise of seric
We conducted an analysis to reevaluate the in vitroculture inhibition assays as a reliable criter... more We conducted an analysis to reevaluate the in vitroculture inhibition assays as a reliable criteria of functional activity of anti-P. falcipanrm antibodies in premunized individuals. Several strains of P. falcipanrm adapted to in vitro culture were compared, and various technical conditions of parasite growth factors such as culture medium or incubation conditions were explored. A subsequent degree of variation was evidenced related to the parasite strain used and the culture conditions. The culture inhibition and the merozoite reinvasion inhibition assays were performed using a collection of plasma from premunized individuals living in two different endemic area of transmission in Senegal. High levels of inhibition were evidenced with a limited degree of variation according to the two different locations of individual's samples. A Significant relationship between anti-merozoite Ab levels and the culture inhibition assays was found contrary to the merozoite re-invasion inhibitio...
The spread ofPlasmodium falciparumresistance toward most of the used drugs requires new antimalar... more The spread ofPlasmodium falciparumresistance toward most of the used drugs requires new antimalarial compounds. Taking advantage of the biodiversity, the ethnopharmacological approach opens the way for the discovery and the characterization of potent original molecules. Previous works led to the selection of a bisbenzylisoquinoline, cepharanthine, extracted fromStephania rotunda, which is mainly present in Cambodia. A sensitive and selective liquid chromatography method has been developed for the determination of cepharanthine in mouse plasma. The method involved a semiautomated microextraction by packed sorbent (MEPS) using 4 mg of solid phase silica-C8 sorbent. LC separation was performed on a Kinetex XB-C18 column (2.6 µm) with a mobile phase of acetonitrile containing formic acid and 10 mM ammonium formate buffer pH 3.5. Data were acquired at 282 nm with a diode array detector. The drug/internal standard peak area ratios were linked via linear relationships to plasma concentrati...
A simple gradient reversed phase high performance liquid chromatographic method was developed for... more A simple gradient reversed phase high performance liquid chromatographic method was developed for the determination of ambroxol hydrochloride in presence of antimicrobial preservatives in oral liquid formulation. The chromatographic separation was achieved by an Inertsil C 8 (250 X 4.6 mm, 5µ particle size) column using gradient technique. The eluents were detected at 245 nm with photodiode array detector. The optimized mobile phase consisted of 0.1% trifluoroacetic acid as a mobile phase A and a mixture of mobile phase A and acetonitrile in the ratio of 76:24 % v/v as mobile phase B. Ambroxol hydrochloride and microbial preservatives were eluted at a flow rate of 1.0 ml/min. The method validated according to the International Conference of Harmonization (ICH) guidelines. The calibration curves were linear over the (r 2 > 0.99) concentrations range from 300 to 900 ppm for ambroxol hydrochloride, 10 to 30 ppm for propyl paraben and 100 to 300 ppm for methyl paraben. The limit of detection was found to be 0.024 ppm for ambroxol hydrochloride, 0.018 ppm for propyl paraben and 0.009 ppm for methyl paraben. The percentage recoveries were found to be in the range from 99.55 to 101.1% for ambroxol hydrochloride, 100.31 to 101.46% for propyl paraben and 98.18 to 101.61% for methyl paraben. Stability indicating capability was established by forced degradation experiments. No chromatographic interference from the degradation products was found. The proposed method was highly sensitive, precision and accurate and hence successfully applied for the quantification of ambroxol active pharmaceutical ingredients (API) and preservatives content in the commercially available oral liquid formulation.
The effects of a series of dihydroethano- and ethenoanthracene derivatives on chloroquine (CQ) ac... more The effects of a series of dihydroethano- and ethenoanthracene derivatives on chloroquine (CQ) accumulation in CQ-susceptible strain 3D7 and CQ-resistant clone W2 were assessed. The levels of CQ accumulation increased little or none in CQ-susceptible strain 3D7 and generally increased markedly in CQ-resistant strain W2. At 10 μM, 28 compounds yielded cellular accumulation ratios (CARs) greater than that observed with CQ alone in W2. At 10 μM, in strain W2, 21 of 31 compounds had CQ CARs two or more times higher than that of CQ alone, 15 of 31 compounds had CQ CARs three or more times higher than that of CQ alone, 13 of 31 compounds had CQ CARs four or more times higher than that of CQ alone, and 9 of 31 compounds had CQ CARs five or more times higher than that of CQ alone. At 1 μM, 17 of 31 compounds had CQ CARs two or more times higher than that of CQ alone, 12 of 31 compounds had CQ CARs three or more times higher than that of CQ alone, 6 of 31 compounds had CQ CARs four or more t...
Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences)... more Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
The in vitro activity of pyronaridine was evaluated against 62 isolates of Plasmodium falciparumf... more The in vitro activity of pyronaridine was evaluated against 62 isolates of Plasmodium falciparumfrom Libreville, Gabon using an isotopic, drug susceptibility microtest and was compared with amodiaquine, chloroquine, quinine, and halofantrine activities. The mean 50% inhibitory concentration (IC 50) values of the 62 isolates from Gabon to pyronaridine was 3.0 nM (95% confidence interval (CI)5 2.1-3.9). Pyronaridine was less potent
The in vitro activity of artemether against 63 African isolates of Plasmodium falciparum from Lib... more The in vitro activity of artemether against 63 African isolates of Plasmodium falciparum from Libreville, Gabon was evaluated using an isotopic drug susceptibility semi-microtest. The 50% inhibitory concentration (IC50) values for artemether were in a narrow range from 0.8 to 34.8 nM (mean IC50 5.0 nM) and the 95% confidence interval (CI95%) was 3.6-6.3 nM. In vitro decreased susceptibility or resistance were observed with artemether (14%), to chloroquine (90%), to quinine (32%). Isolate susceptibility to amodiaquine and halofantrine was high i.e. 100% and 98%, respectively. There was a significant positive correlation between responses to artemether and amodiaquine (r2 = 0.45, P < 0.001), artemether and chloroquine (r2 = 0.36, P < 0.001), artemether and quinine (r2 = 0.31, P < 0.001), and artemether and halofantrine (r2 = 0.19, P < 0.01). Positive correlation between these drugs suggests in vitro cross-resistance or at least common features in drug uptake and/or mode of action or resistance.
The 50% inhibitory concentration (IC50s) of benflumetol (range, 12.5 to 240 nM; mean, 55.1 nM) fo... more The 50% inhibitory concentration (IC50s) of benflumetol (range, 12.5 to 240 nM; mean, 55.1 nM) for 158 Senegalese isolates were evaluated. Ten isolates (6%) showed decreased susceptibility to benflumetol. Benflumetol was slightly more potent against chloroquine-resistant isolates (P < 0.025). No correlation or weak correlations in the responses to benflumetol and pyrimethamine, chloroquine, amodiaquine, artemether, quinine, and pyronaridine were observed, and these correlations are insufficient to suggest cross-resistance. Benflumetol may be an important alternative drug for the treatment of chloroquine-resistant malaria.
We examined the atovaquone in vitro susceptibility and the cytochrome b (cytb) gene polymorphism ... more We examined the atovaquone in vitro susceptibility and the cytochrome b (cytb) gene polymorphism of African Plasmodium falciparum isolates during the first years of atovaquone/proguanil use. Patients and methods: Between 1999 and 2004, we collected blood samples from French P. falciparuminfected patients returning from African countries. Atovaquone susceptibility was determined using an in vitro isotopic test and cytb genotyping was performed by restriction fragment length polymorphism analysis and sequencing. These results were analysed according to the clinical response to atovaquone/ proguanil treatment. Results: No in vitro atovaquone resistance (IC 50 > 1900 nM) and no cytb mutation leading to the Y268S substitution were detected among 477 unexposed African P. falciparum isolates. Eight cytb polymorphisms were found outside the ubiquinone reduction site by sequencing the entire gene of 270 isolates. One atovaquone/proguanil treatment failure was documented; the post-treatment isolate had an atovaquone susceptibility of 8230 nM and the Ser 268 Cytb change; the pre-treatment isolate, obtained 4 weeks previously, was Cytb Tyr 268 (wild-type). Conclusions: No atovaquone/proguanil resistance was detected by phenotyping or genotyping among 477 unexposed African P. falciparum isolates. Atovaquone/proguanil-resistant parasite was detectable only in the post-treatment isolate from a treatment failure.
The in vitro activities of cyclines (tetracycline, doxycycline, minocycline, oxytetracycline, and... more The in vitro activities of cyclines (tetracycline, doxycycline, minocycline, oxytetracycline, and rolitetracycline), macrolides (erythromycin, spiramycin, roxithromycin, and lincomycin), quinolones (norfloxacin and ofloxacin), rifampin, thiamphenicol, tobramycin, metronidazole, vancomycin, phosphomycin, and cephalosporins (cephalexin, cefaclor, cefamandole, cefuroxime, ceftriazone, cefotaxime, and cefoxitin) were evaluated on Plasmodium falciparum clones, using an isotopic, micro-drug susceptibility test. Only tetracyclines, macrolides, quinolones, and rifampin demonstrated in vitro activity against P. falciparum, which increased after a prolonged exposure (96 or 144 h). In the presence of iron (FeCl 3 ), only the activities of tetracyclines and norfloxacin were decreased. Their in vitro activity against intraerythrocytic stages of multidrug-resistant P. falciparum and their efficacy in vivo favor the use of antibiotics as antimalarial drugs. However, due to their slow antimalarial action and to the fact that they act better after prolonged contact, they probably need to be administered in conjunction with a rapidly acting antimalarial drug, such as a short course of chloroquine or quinine.
Background: Over its life cycle, the Plasmodium falciparum parasite is exposed to different envir... more Background: Over its life cycle, the Plasmodium falciparum parasite is exposed to different environmental conditions, particularly to variations in O 2 pressure. For example, the parasite circulates in human venous blood at 5% O 2 pressure and in arterial blood, particularly in the lungs, at 13% O 2 pressure. Moreover, the parasite is exposed to 21% O 2 levels in the salivary glands of mosquitoes. Methods: To study the metabolic adaptation of P. falciparum to different oxygen pressures during the intraerythrocytic cycle, a combined approach using transcriptomic and proteomic techniques was undertaken.
Objectives. – The aim of this work was to study the chemosensitivity of Plasmodium falciparum str... more Objectives. – The aim of this work was to study the chemosensitivity of Plasmodium falciparum strains isolated from patients presenting with malaria after having returned from Comoros Islands in 2002–2003, and hospitalized at the North University Hospital, in Marseilles, France.Materials and methods. – In vitro drug susceptibility (for strains maintained in culture) and mutation-specific polymerase chain reaction (PCR) assays (for
Epidemiological (cohort follow-up) and laboratory techniques studies were done to validate a prog... more Epidemiological (cohort follow-up) and laboratory techniques studies were done to validate a programme of chemoprevention of canine monocytic ehrlichiosis (CME) with this molecule. 614 dogs returning to France after having spent at least 4 months in a CME-endemic area (Africa, Guyana, Middle-East, etc.) were the object of systematic serological testing by indirect immunofluorescence (IFA). The dogs were given 100 mg of doxycycline per os daily for chemoprevention of CME. In addition, HPLC (high performance liquid chromatography) was used to determine plasma levels of doxycycline in 124 of the dogs. The CEM mortality and morbidity rates for the 614 dogs in the chemoprevention programme were nil. The seroconversion rate was 4% (24/614). Seropositive dogs (low titres) were asymptomatic and generally became seronegative after treatment. A study done on 10 dogs shows that doxycyclinaemia was 1.2 (0.94-1.53) microg/ml 2 h after the drug had been administered. After 24 h, the residual concentration was 0.34 (0.26-0.44) microg/ml. Blind doxycyclinaemia tests done on 110 dogs living in Africa (the results for four dogs were nil and therefore eliminated from the study) showed that the minimum observed concentration was always greater than 0.2 microg/ml. Given that, as concerns infection with Ehrlichia spp., the minimum inhibitory concentration of doxycycline is &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 0.03 microg/ml, dogs receiving chemoprevention treatment should be protected.
The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amod... more The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amodiaquine, artesunate, atovaquone, cycloguanil and pyrimethamine were evaluated against Plasmodium falciparum isolates from Senegal (Dielmo, Ndiop), using an isotopic micro-drug susceptibility test. The IC50 values for ferrochloroquine ranged from 0.55 to 28.2 nM and the geometric mean IC50 for the 55 isolates was 7.9 nM (95% CI, 6.5-9.7 nM). Ferrochloroquine was 35 times more active than chloroquine (35-fold greater against chloroquine-resistant isolates), quinine, mefloquine, amodiaquine, cycloguanil and pyrimethamine. Weak positive correlations were observed between the responses to ferrochloroquine and that to chloroquine, quinine, and amodiaquine, but not compulsorily predictive of cross-resistance. There was no significant correlation between the response to ferrochloroquine and that to mefloquine, halofantrine, artesunate, atovaquone, cycloguanil and pyrimethamine. Ferrochloroquine may be an important alternative drug for the treatment of chloroquine-resistant malaria.
The emergence and dissemination of drug-resistant malaria parasites represent one of the most imp... more The emergence and dissemination of drug-resistant malaria parasites represent one of the most important problems in malaria case management. Plasmodium falciparum is the causative agent of the most lethal form of human malaria. The molecular mechanisms that control the life cycle of the malaria parasite are still poorly understood. The published genome sequence (P. falciparum strain 3D7) reveals that several homologs of eukaryotic signaling proteins, such as protein kinases and phosphatases, are conserved in P. falciparum. Proteins kinases are now widely recognized as valuable drug targets in protozoan parasites. In this study, gene silencing with double-stranded RNA (dsRNA) and microarray techniques were used to study the biological function of the cAMP-dependent protein kinase catalytic subunit (PfPKAc) in the parasite erythrocytic life cycle. Treatment of parasites with PfPKAc dsRNA resulted in a marked reduction of endogenous PfPKAc mRNA associated with a compensatory decrease of PfPKAr mRNA followed by morphological changes in schizont stages and cell cycle arrest. The global effects of gene silencing were also investigated using a P. falciparum pan-genomic microarray. Transcriptomic analysis showed that the expression of 329 genes was altered in response to downregulation of PfPKAc mRNA particularly genes in specific metabolic pathways linked with merozoite invasion processes, the calcium/calmodulin signaling, and kinases network and mitochondrial functions.
´veloppement, Dakar, Senegal Abstract. The in vitro activities of doxycycline, chloroquine, quini... more ´veloppement, Dakar, Senegal Abstract. The in vitro activities of doxycycline, chloroquine, quinine, amodiaquine, artemether, pyrimethamine, and cycloguanil were evaluated against Plasmodium falciparumisolates from Senegal (Dielmo and Ndiop), using an isotopic, micro, drug susceptibility test. The 71 50% inhibitory concentration (IC 50) values for doxycycline ranged from 0.7 to 108.0 M and the geometric mean IC50 for the 71 isolates was
The effectsof combining four dihydroethanoanthracenic (DEA) derivativ esand chloroquine were as -... more The effectsof combining four dihydroethanoanthracenic (DEA) derivativ esand chloroquine were as - sessed in vitro against Plasmodium falciparum chloroquine resistant parasites W2, Palo Alto, FCR3, and Bres1. Like verapamil or promethazine, the four dihydroethanoanthracenic derivatives tested can be added to the growing list of agentsthat s how capability in enhancing the activity of chloroquine agai nst resistant parasites. The structurally
Our objective was to evaluate the efficacy of fipronil for the prevention of Ehrlichia canis tran... more Our objective was to evaluate the efficacy of fipronil for the prevention of Ehrlichia canis transmission to dogs by Rhipicephalus sanguineus in two endemic areas situated in Africa (Dakar and Djibouti). We carried out controlled trials in kennels for 1 year on 248 dogs, mainly police dogs and military working dogs. Eight groups were studied in a multi-centre study. Fifty
Canine monocytic ehrlichiosis is an infectious worldwide disease caused by small obligatory intra... more Canine monocytic ehrlichiosis is an infectious worldwide disease caused by small obligatory intramonocytic bacterium (Ehrlichia canis) transmitted by ticks (Rhipicephalus sanguineus). The infection is characterized by non specific clinical signs (hyperthermia, anorexia…) which can only orient the veterinary practician towards a presumptive diagnosis. The main biological signs associated with canine ehrlichiosis are thrombocytopenia, leucopenia or leucocytosis, anemia, rise of seric
We conducted an analysis to reevaluate the in vitroculture inhibition assays as a reliable criter... more We conducted an analysis to reevaluate the in vitroculture inhibition assays as a reliable criteria of functional activity of anti-P. falcipanrm antibodies in premunized individuals. Several strains of P. falcipanrm adapted to in vitro culture were compared, and various technical conditions of parasite growth factors such as culture medium or incubation conditions were explored. A subsequent degree of variation was evidenced related to the parasite strain used and the culture conditions. The culture inhibition and the merozoite reinvasion inhibition assays were performed using a collection of plasma from premunized individuals living in two different endemic area of transmission in Senegal. High levels of inhibition were evidenced with a limited degree of variation according to the two different locations of individual's samples. A Significant relationship between anti-merozoite Ab levels and the culture inhibition assays was found contrary to the merozoite re-invasion inhibitio...
The spread ofPlasmodium falciparumresistance toward most of the used drugs requires new antimalar... more The spread ofPlasmodium falciparumresistance toward most of the used drugs requires new antimalarial compounds. Taking advantage of the biodiversity, the ethnopharmacological approach opens the way for the discovery and the characterization of potent original molecules. Previous works led to the selection of a bisbenzylisoquinoline, cepharanthine, extracted fromStephania rotunda, which is mainly present in Cambodia. A sensitive and selective liquid chromatography method has been developed for the determination of cepharanthine in mouse plasma. The method involved a semiautomated microextraction by packed sorbent (MEPS) using 4 mg of solid phase silica-C8 sorbent. LC separation was performed on a Kinetex XB-C18 column (2.6 µm) with a mobile phase of acetonitrile containing formic acid and 10 mM ammonium formate buffer pH 3.5. Data were acquired at 282 nm with a diode array detector. The drug/internal standard peak area ratios were linked via linear relationships to plasma concentrati...
A simple gradient reversed phase high performance liquid chromatographic method was developed for... more A simple gradient reversed phase high performance liquid chromatographic method was developed for the determination of ambroxol hydrochloride in presence of antimicrobial preservatives in oral liquid formulation. The chromatographic separation was achieved by an Inertsil C 8 (250 X 4.6 mm, 5µ particle size) column using gradient technique. The eluents were detected at 245 nm with photodiode array detector. The optimized mobile phase consisted of 0.1% trifluoroacetic acid as a mobile phase A and a mixture of mobile phase A and acetonitrile in the ratio of 76:24 % v/v as mobile phase B. Ambroxol hydrochloride and microbial preservatives were eluted at a flow rate of 1.0 ml/min. The method validated according to the International Conference of Harmonization (ICH) guidelines. The calibration curves were linear over the (r 2 > 0.99) concentrations range from 300 to 900 ppm for ambroxol hydrochloride, 10 to 30 ppm for propyl paraben and 100 to 300 ppm for methyl paraben. The limit of detection was found to be 0.024 ppm for ambroxol hydrochloride, 0.018 ppm for propyl paraben and 0.009 ppm for methyl paraben. The percentage recoveries were found to be in the range from 99.55 to 101.1% for ambroxol hydrochloride, 100.31 to 101.46% for propyl paraben and 98.18 to 101.61% for methyl paraben. Stability indicating capability was established by forced degradation experiments. No chromatographic interference from the degradation products was found. The proposed method was highly sensitive, precision and accurate and hence successfully applied for the quantification of ambroxol active pharmaceutical ingredients (API) and preservatives content in the commercially available oral liquid formulation.
The effects of a series of dihydroethano- and ethenoanthracene derivatives on chloroquine (CQ) ac... more The effects of a series of dihydroethano- and ethenoanthracene derivatives on chloroquine (CQ) accumulation in CQ-susceptible strain 3D7 and CQ-resistant clone W2 were assessed. The levels of CQ accumulation increased little or none in CQ-susceptible strain 3D7 and generally increased markedly in CQ-resistant strain W2. At 10 μM, 28 compounds yielded cellular accumulation ratios (CARs) greater than that observed with CQ alone in W2. At 10 μM, in strain W2, 21 of 31 compounds had CQ CARs two or more times higher than that of CQ alone, 15 of 31 compounds had CQ CARs three or more times higher than that of CQ alone, 13 of 31 compounds had CQ CARs four or more times higher than that of CQ alone, and 9 of 31 compounds had CQ CARs five or more times higher than that of CQ alone. At 1 μM, 17 of 31 compounds had CQ CARs two or more times higher than that of CQ alone, 12 of 31 compounds had CQ CARs three or more times higher than that of CQ alone, 6 of 31 compounds had CQ CARs four or more t...
Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences)... more Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
The in vitro activity of pyronaridine was evaluated against 62 isolates of Plasmodium falciparumf... more The in vitro activity of pyronaridine was evaluated against 62 isolates of Plasmodium falciparumfrom Libreville, Gabon using an isotopic, drug susceptibility microtest and was compared with amodiaquine, chloroquine, quinine, and halofantrine activities. The mean 50% inhibitory concentration (IC 50) values of the 62 isolates from Gabon to pyronaridine was 3.0 nM (95% confidence interval (CI)5 2.1-3.9). Pyronaridine was less potent
The in vitro activity of artemether against 63 African isolates of Plasmodium falciparum from Lib... more The in vitro activity of artemether against 63 African isolates of Plasmodium falciparum from Libreville, Gabon was evaluated using an isotopic drug susceptibility semi-microtest. The 50% inhibitory concentration (IC50) values for artemether were in a narrow range from 0.8 to 34.8 nM (mean IC50 5.0 nM) and the 95% confidence interval (CI95%) was 3.6-6.3 nM. In vitro decreased susceptibility or resistance were observed with artemether (14%), to chloroquine (90%), to quinine (32%). Isolate susceptibility to amodiaquine and halofantrine was high i.e. 100% and 98%, respectively. There was a significant positive correlation between responses to artemether and amodiaquine (r2 = 0.45, P &lt; 0.001), artemether and chloroquine (r2 = 0.36, P &lt; 0.001), artemether and quinine (r2 = 0.31, P &lt; 0.001), and artemether and halofantrine (r2 = 0.19, P &lt; 0.01). Positive correlation between these drugs suggests in vitro cross-resistance or at least common features in drug uptake and/or mode of action or resistance.
The 50% inhibitory concentration (IC50s) of benflumetol (range, 12.5 to 240 nM; mean, 55.1 nM) fo... more The 50% inhibitory concentration (IC50s) of benflumetol (range, 12.5 to 240 nM; mean, 55.1 nM) for 158 Senegalese isolates were evaluated. Ten isolates (6%) showed decreased susceptibility to benflumetol. Benflumetol was slightly more potent against chloroquine-resistant isolates (P < 0.025). No correlation or weak correlations in the responses to benflumetol and pyrimethamine, chloroquine, amodiaquine, artemether, quinine, and pyronaridine were observed, and these correlations are insufficient to suggest cross-resistance. Benflumetol may be an important alternative drug for the treatment of chloroquine-resistant malaria.
We examined the atovaquone in vitro susceptibility and the cytochrome b (cytb) gene polymorphism ... more We examined the atovaquone in vitro susceptibility and the cytochrome b (cytb) gene polymorphism of African Plasmodium falciparum isolates during the first years of atovaquone/proguanil use. Patients and methods: Between 1999 and 2004, we collected blood samples from French P. falciparuminfected patients returning from African countries. Atovaquone susceptibility was determined using an in vitro isotopic test and cytb genotyping was performed by restriction fragment length polymorphism analysis and sequencing. These results were analysed according to the clinical response to atovaquone/ proguanil treatment. Results: No in vitro atovaquone resistance (IC 50 > 1900 nM) and no cytb mutation leading to the Y268S substitution were detected among 477 unexposed African P. falciparum isolates. Eight cytb polymorphisms were found outside the ubiquinone reduction site by sequencing the entire gene of 270 isolates. One atovaquone/proguanil treatment failure was documented; the post-treatment isolate had an atovaquone susceptibility of 8230 nM and the Ser 268 Cytb change; the pre-treatment isolate, obtained 4 weeks previously, was Cytb Tyr 268 (wild-type). Conclusions: No atovaquone/proguanil resistance was detected by phenotyping or genotyping among 477 unexposed African P. falciparum isolates. Atovaquone/proguanil-resistant parasite was detectable only in the post-treatment isolate from a treatment failure.
The in vitro activities of cyclines (tetracycline, doxycycline, minocycline, oxytetracycline, and... more The in vitro activities of cyclines (tetracycline, doxycycline, minocycline, oxytetracycline, and rolitetracycline), macrolides (erythromycin, spiramycin, roxithromycin, and lincomycin), quinolones (norfloxacin and ofloxacin), rifampin, thiamphenicol, tobramycin, metronidazole, vancomycin, phosphomycin, and cephalosporins (cephalexin, cefaclor, cefamandole, cefuroxime, ceftriazone, cefotaxime, and cefoxitin) were evaluated on Plasmodium falciparum clones, using an isotopic, micro-drug susceptibility test. Only tetracyclines, macrolides, quinolones, and rifampin demonstrated in vitro activity against P. falciparum, which increased after a prolonged exposure (96 or 144 h). In the presence of iron (FeCl 3 ), only the activities of tetracyclines and norfloxacin were decreased. Their in vitro activity against intraerythrocytic stages of multidrug-resistant P. falciparum and their efficacy in vivo favor the use of antibiotics as antimalarial drugs. However, due to their slow antimalarial action and to the fact that they act better after prolonged contact, they probably need to be administered in conjunction with a rapidly acting antimalarial drug, such as a short course of chloroquine or quinine.
Background: Over its life cycle, the Plasmodium falciparum parasite is exposed to different envir... more Background: Over its life cycle, the Plasmodium falciparum parasite is exposed to different environmental conditions, particularly to variations in O 2 pressure. For example, the parasite circulates in human venous blood at 5% O 2 pressure and in arterial blood, particularly in the lungs, at 13% O 2 pressure. Moreover, the parasite is exposed to 21% O 2 levels in the salivary glands of mosquitoes. Methods: To study the metabolic adaptation of P. falciparum to different oxygen pressures during the intraerythrocytic cycle, a combined approach using transcriptomic and proteomic techniques was undertaken.
Objectives. – The aim of this work was to study the chemosensitivity of Plasmodium falciparum str... more Objectives. – The aim of this work was to study the chemosensitivity of Plasmodium falciparum strains isolated from patients presenting with malaria after having returned from Comoros Islands in 2002–2003, and hospitalized at the North University Hospital, in Marseilles, France.Materials and methods. – In vitro drug susceptibility (for strains maintained in culture) and mutation-specific polymerase chain reaction (PCR) assays (for
Epidemiological (cohort follow-up) and laboratory techniques studies were done to validate a prog... more Epidemiological (cohort follow-up) and laboratory techniques studies were done to validate a programme of chemoprevention of canine monocytic ehrlichiosis (CME) with this molecule. 614 dogs returning to France after having spent at least 4 months in a CME-endemic area (Africa, Guyana, Middle-East, etc.) were the object of systematic serological testing by indirect immunofluorescence (IFA). The dogs were given 100 mg of doxycycline per os daily for chemoprevention of CME. In addition, HPLC (high performance liquid chromatography) was used to determine plasma levels of doxycycline in 124 of the dogs. The CEM mortality and morbidity rates for the 614 dogs in the chemoprevention programme were nil. The seroconversion rate was 4% (24/614). Seropositive dogs (low titres) were asymptomatic and generally became seronegative after treatment. A study done on 10 dogs shows that doxycyclinaemia was 1.2 (0.94-1.53) microg/ml 2 h after the drug had been administered. After 24 h, the residual concentration was 0.34 (0.26-0.44) microg/ml. Blind doxycyclinaemia tests done on 110 dogs living in Africa (the results for four dogs were nil and therefore eliminated from the study) showed that the minimum observed concentration was always greater than 0.2 microg/ml. Given that, as concerns infection with Ehrlichia spp., the minimum inhibitory concentration of doxycycline is &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 0.03 microg/ml, dogs receiving chemoprevention treatment should be protected.
The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amod... more The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amodiaquine, artesunate, atovaquone, cycloguanil and pyrimethamine were evaluated against Plasmodium falciparum isolates from Senegal (Dielmo, Ndiop), using an isotopic micro-drug susceptibility test. The IC50 values for ferrochloroquine ranged from 0.55 to 28.2 nM and the geometric mean IC50 for the 55 isolates was 7.9 nM (95% CI, 6.5-9.7 nM). Ferrochloroquine was 35 times more active than chloroquine (35-fold greater against chloroquine-resistant isolates), quinine, mefloquine, amodiaquine, cycloguanil and pyrimethamine. Weak positive correlations were observed between the responses to ferrochloroquine and that to chloroquine, quinine, and amodiaquine, but not compulsorily predictive of cross-resistance. There was no significant correlation between the response to ferrochloroquine and that to mefloquine, halofantrine, artesunate, atovaquone, cycloguanil and pyrimethamine. Ferrochloroquine may be an important alternative drug for the treatment of chloroquine-resistant malaria.
The emergence and dissemination of drug-resistant malaria parasites represent one of the most imp... more The emergence and dissemination of drug-resistant malaria parasites represent one of the most important problems in malaria case management. Plasmodium falciparum is the causative agent of the most lethal form of human malaria. The molecular mechanisms that control the life cycle of the malaria parasite are still poorly understood. The published genome sequence (P. falciparum strain 3D7) reveals that several homologs of eukaryotic signaling proteins, such as protein kinases and phosphatases, are conserved in P. falciparum. Proteins kinases are now widely recognized as valuable drug targets in protozoan parasites. In this study, gene silencing with double-stranded RNA (dsRNA) and microarray techniques were used to study the biological function of the cAMP-dependent protein kinase catalytic subunit (PfPKAc) in the parasite erythrocytic life cycle. Treatment of parasites with PfPKAc dsRNA resulted in a marked reduction of endogenous PfPKAc mRNA associated with a compensatory decrease of PfPKAr mRNA followed by morphological changes in schizont stages and cell cycle arrest. The global effects of gene silencing were also investigated using a P. falciparum pan-genomic microarray. Transcriptomic analysis showed that the expression of 329 genes was altered in response to downregulation of PfPKAc mRNA particularly genes in specific metabolic pathways linked with merozoite invasion processes, the calcium/calmodulin signaling, and kinases network and mitochondrial functions.
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Papers by Daniel Parzy