Souleymane Dama

University of Bamako, Bamako, District de Bamako, Mali

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Publications (9)30.07 Total impact

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    ABSTRACT: Background. The mechanism of Plasmodium falciparum resistance to quinine is not known. In vitro QTL mapping suggests involvement of a predicted P. falciparum sodiumhydrogen exchanger (pfnhe1) on chromosome 13.Methods. We conducted prospective quinine efficacy studies in two villages, Kollé and Faladié, Mali. Cases of clinical malaria requiring intravenous therapy were treated with standard doses of quinine and followed for 28 days. Treatment outcomes were classified using modified World Health Organization protocols. Molecular markers of parasite polymorphisms were used to distinguish recrudescent parasites from new infections. Prevalence of pfnhe1 ms47601 in infections before vs. after quinine treatment was determined by directsequencing.Results. Overall, 163 patients were enrolled and successfully followed. Without molecular correction, the mean ACPR was 50.3% (n = 163). After PCR correction to account for new infections, corrected ACPR was 100%. Prevalence of ms47601increased significantly from 26.2% (n = 107) before quinine treatment to 46.3% (n = 54) after therapy (P = 0.01). In a control sulfadoxinepyrimethamine study, prevalence of ms47601 was similar before and after treatment.Conclusions. This study supports a role for pfnhe1 in decreased susceptibility of P. falciparum to quinine in the field.
    The Journal of Infectious Diseases 11/2012; · 5.85 Impact Factor
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    ABSTRACT: Background. The mechanism of Plasmodium falciparum resistance to quinine is not known. In vitro quantitative trait loci mapping suggests involvement of a predicted P. falciparum sodium-hydrogen exchanger (pfnhe-1) on chromosome 13. Methods. We conducted prospective quinine efficacy studies in 2 villages, Kollé and Faladié, Mali. Cases of clinical malaria requiring intravenous therapy were treated with standard doses of quinine and followed for 28 days. Treatment outcomes were classified using modified World Health Organization protocols. Molecular markers of parasite polymorphisms were used to distinguish recrudescent parasites from new infections. The prevalence of pfnhe-1 ms4760-1 among parasites before versus after quinine treatment was determined by direct sequencing. Results. Overall, 163 patients were enrolled and successfully followed. Without molecular correction, the mean adequate clinical and parasitological response (ACPR) was 50.3% (n = 163). After polymerase chain reaction correction to account for new infections, the corrected ACPR was 100%. The prevalence of ms4760-1 increased significantly, from 26.2% (n= 107) before quinine treatment to 46.3% (n = 54) after therapy (P = .01). In a control sulfadoxine-pyrimethamine study, the prevalence of ms4760-l was similar before and after treatment. Conclusions. This study supports a role for pfnhe-l in decreased susceptibility of P. falciparum to quinine in the field.
    The Journal of Infectious Diseases 09/2012; The Journal of Infectious Diseases(#49881R1). · 5.85 Impact Factor
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    ABSTRACT: Plasmodium falciparum resistance to artemisinins by delayed parasite clearance is present in Southeast Asia. Scant data on parasite clearance after artemisinins are available from Africa, where transmission is high, burden is greatest, and artemisinin use is being scaled up. Children 1-10 years of age with uncomplicated malaria were treated with 7 days of artesunate and followed for 28 days. Blood smears were done every 8 hours until negative by light microscopy. Results were compared with a similar study conducted in the same village in 2002-2004. The polymerase chain reaction-corrected cure rate was 100%, identical to 2002-2004. By 24 hours after treatment initiation, 37.0% of participants had cleared parasitemia, compared with 31.9% in 2002-2004 (P = 0.5). The median parasite clearance time was 32 hours. Only one participant still had parasites at 48 hours and no participant presented parasitemia at 72 hours. Artesunate was highly efficacious, with no evidence of delayed parasite clearance. We provide baseline surveillance data for the emergence or dissemination of P. falciparum resistance in sub-Saharan Africa.
    The American journal of tropical medicine and hygiene 07/2012; 87(1):23-8. · 2.53 Impact Factor
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    ABSTRACT: Background Neonatal malaria is classicaly known to be rare in malaria endemic countries. However, reports increasingly suggest an underestimation of its true frequency. The aim of this study was to determine the prevalence of congenital and neonatal malaria in infants admitted in tertiary reference hospital in Mali using three complementary diagnostic methods. Methods The study was conducted in neonatalogy unit of the pediatric ward of the teaching hospital Gabriel Toure in Bamako, Mali from October 1st 2006 to March 17th 2008. In-patient infants aged between 0 and 28 days and their mothers were included. Malaria was diagnosed on infants and mothers venous blood using a rapid diagnostic test (RDT, OptiMAL IT®), light microscopy of thick smear and polymerase chain reaction (PCR). Results Overall 267 infants and 146 mothers were included. The mean age and weight of the infants were 2.7 days and 2862.4 g respectively. Light microscopy of thick smears and PCR amplification of parasite DNA were both negative in the infant population. Mothers had a mean age of 25 years. Microscopy of thick smears was negative in all samples collected from these mothers while the RDT detected one case of Plasmodium falciparum and PCR detected seven cases of P. falciparum and two cases of P. ovale. Conclusion Congenital and neonatal malaria remain of a rare occurrence in in-patients infants admitted in a tertiary reference hospital in Mali.
    Health Policy. 01/2011; 24(2):57-61.
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    ABSTRACT: Plasmodium falciparum chloroquine resistance (CQR) transporter point mutation (PfCRT 76T) is known to be the key determinant of CQR. Molecular detection of PfCRT 76T in field samples may be used for the surveillance of CQR in malaria-endemic countries. The genotype-resistance index (GRI), which is obtained as the ratio of the prevalence of PfCRT 76T to the incidence of CQR in a clinical trial, was proposed as a simple and practical molecular-based addition to the tools currently available for monitoring CQR in the field. In order to validate the GRI model across populations, time, and resistance patterns, we compiled data from the literature and generated new data from 12 sites across Mali. We found a mean PfCRT 76T mutation prevalence of 84.5% (range 60.9-95.1%) across all sites. CQR rates predicted from the GRI model were extrapolated onto a map of Mali to show the patterns of resistance throughout the participating regions. We present a comprehensive map of CQR in Mali, which strongly supports recent changes in drug policy away from chloroquine.
    FEMS Immunology & Medical Microbiology 02/2010; 58(1):113-8. · 2.68 Impact Factor
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    ABSTRACT: Intermittent preventive treatment in infants (IPTi) with sulphadoxine-pyrimethamine (SP) given during routine vaccinations is efficacious in preventing malaria disease and shows no interaction with the vaccines. However, there is a fear that IPTi may result in a rapid increase of parasite resistance to SP. To evaluate the impact of IPTi on SP-resistance point mutations, the 22 health sub-districts in the district of Kolokani, Mali, were randomized in a 1:1 ratio and starting in December 2006, IPTi with SP was implemented in 11 health sub-districts (intervention zone), while the other 11 health sub-districts served as the control (non-intervention zone). Blood smears and blood dots on filter paper were obtained from children aged 0-5 years, randomly selected in each of heath sub-districts during two cross-sectional surveys. The first survey was conducted in May 2007 before the start of the transmission season to collect baseline prevalence of the molecular markers of resistance to SP and the second in December 2007 after the end of the transmission season and one year after implementation of IPTi. A total of 427 and 923 randomly selected blood samples from the first and second surveys respectively were analysed by PCR for dhfr and dhps mutations. Each of the three dhfr mutations at codons 51, 59 and 108 was present in 35% and 57% of the samples during the two surveys with no significant differences between the two zones. Dhps mutations at codons 437 and 540 were present respectively in about 20% and 1% of the children during the two surveys in both zones at similar proportion. The prevalence of quadruple mutants (triple dhfr-mutants + dhps-437G) associated with in-vivo resistance to SP in Mali after one year implementation of IPTi was also similar between the two zones (11.6% versus 11.2%, p = 0.90) and to those obtained at baseline survey (10.3% versus 8.1%). This study shows no increase in the frequency of molecular markers of SP resistance in areas where IPTi with SP was implemented for one year.
    Malaria Journal 01/2010; 9:9. · 3.49 Impact Factor
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    ABSTRACT: To update the National Malaria Control Programme of Mali on the efficacy of chloroquine, amodiaquine and sulphadoxine-pyrimethamine in the treatment of uncomplicated falciparum malaria. During the malaria transmission seasons of 2002 and 2003, 455 children--between six and 59 months of age, with uncomplicated malaria in Kolle, Mali, were randomly assigned to one of three treatment arms. In vivo outcomes were assessed using WHO standard protocols. Genotyping of msp1, msp2 and CA1 polymorphisms were used to distinguish reinfection from recrudescent parasites (molecular correction). Day 28 adequate clinical and parasitological responses (ACPR) were 14.1%, 62.3% and 88.9% in 2002 and 18.2%, 60% and 85.2% in 2003 for chloroquine, amodiaquine and sulphadoxine-pyrimethamine, respectively. After molecular correction, ACPRs (cACPR) were 63.2%, 88.5% and 98.0% in 2002 and 75.5%, 85.2% and 96.6% in 2003 for CQ, AQ and SP, respectively. Amodiaquine was the most effective on fever. Amodiaquine therapy selected molecular markers for chloroquine resistance, while in the sulphadoxine-pyrimethamine arm the level of dhfr triple mutant and dhfr/dhps quadruple mutant increased from 31.5% and 3.8% in 2002 to 42.9% and 8.9% in 2003, respectively. No infection with dhps 540E was found. In this study, treatment with sulphadoxine-pyrimethamine emerged as the most efficacious on uncomplicated falciparum malaria followed by amodiaquine. The study demonstrated that sulphadoxine-pyrimethamine and amodiaquine were appropriate partner drugs that could be associated with artemisinin derivatives in an artemisinin-based combination therapy.
    Malaria Journal 03/2009; 8:34. · 3.49 Impact Factor
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    ABSTRACT: In vitro susceptibility to antimalarial drugs of Malian Plasmodium falciparum isolates collected between 2004 and 2006 was studied. Susceptibility to chloroquine and to three artemisinin-based combination therapy (ACT) component drugs was assessed as a first, to our knowledge, in vitro susceptibility study in Mali. Overall 96 Malian isolates (51 from around Bamako and 45 collected from French travellers returning from Mali) were cultivated in a CO(2) incubator. Fifty percent inhibitory concentrations (IC(50)s) were measured by either hypoxanthine incorporation or Plasmodium lactate dehydrogenase (pLDH) ELISA. Although the two sets of data were generated with different methods, the global IC(50) distributions showed parallel trends. A good concordance of resistance phenotype with pfcrt 76T mutant genotype was found within the sets of clinical isolates tested. We confirm a high prevalence of P. falciparum in vitro resistance to chloroquine in Mali (60-69%). While some isolates showed IC(50)s close to the cut-off for resistance to monodesethylamodiaquine, no decreased susceptibility to dihydroartemisinin or lumefantrine was detected. This study provides baseline data for P. falciparum in vitro susceptibility to ACT component drugs in Mali.
    International Journal for Parasitology 07/2008; 38(7):791-8. · 3.64 Impact Factor
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    ABSTRACT: We conducted a randomized single-blinded trial comparing the efficacy and safety of artesunate (AS) + amodiaquine (AQ, 3 days) versus AS (3 days) + sulfadoxine-pyrimethamine (SP, single dose) versus AS monotherapy (5 days) in Southern Mali. Uncomplicated malaria cases were followed for 28 days. Molecular markers of drug resistance were determined. After identification of recrudescences by genotyping, both artemisinin-based combination therapies (ACTs) reached nearly 100% efficacy at Day 14 and Day 28 versus 98.3% and 96.5% for AS, respectively (P > 0.05). AS + SP significantly selected DHFR and DHPS mutations associated with sulfadoxine and pyrimethamine resistance (P < 0.001), and AS + AQ equally selected PfCRT and PfMDR1 point mutations associated with chloroquine and AQ resistance (P < 0.001). No significant adverse event attributable to any of the study drugs was found. The ACTs were efficacious and safe, but the selection of markers for resistance to the partner drugs raises concerns over their lifespan in areas of intense malaria transmission.
    The American journal of tropical medicine and hygiene 03/2008; 78(3):455-61. · 2.53 Impact Factor