title: Genotypic and phenotypic characterization of Trypanosoma brucei gambiense isolates from Ibba, South Sudan, an area of high melarsoprol treatment failure rate.
abstract: Resistance of trypanosomes to melarsoprol is ascribed to reduced uptake of the drug via the P2 nucleoside transporter. The aim of this study was to look for evidence of drug resistance in Trypanosoma brucei gambiense isolates from sleeping sickness patients in Ibba, South Sudan, an area of high melarsoprol failure rate. Eighteen T. b. gambiense stocks were phenotypically and only 10 strains genotypically characterized. In vitro, all isolates were sensitive to melarsoprol, melarsen oxide, and diminazene. Infected mice were cured with a 4 day treatment of 2.5mg/kg bwt melarsoprol, confirming that the isolates were sensitive. The gene that codes for the P2 transporter, TbATI, was amplified by PCR and sequenced. The sequences were almost identical to the TbAT1(sensitive) reference, except for one point mutation, C1384T resulting in the amino acid change proline-462 to serine. None of the described TbAT1(resistant)-type mutations were detected. In a T. b. gambiense sleeping sickness focus where melarsoprol had to be abandoned due to the high incidence of treatment failures, no evidence for drug resistant trypanosomes or for TbAT1(resistant)-type alleles of the P2 transporter could be found. These findings indicate that factors other than drug resistance contribute to melarsoprol treatment failures.
authors.affiliation: Trypanosomiasis Research Institute (TRC), PO Box 362, Kikuyu, Kenya.
authors.forename: Naomi
authors.initials: N
authors.lastname: Maina
authors.forename: Kagira Joseph
authors.initials: KJ
authors.lastname: Maina
authors.forename: Pascal
authors.initials: P
authors.lastname: Mäser
authors.forename: Reto
authors.initials: R
authors.lastname: Brun
mesh_terms: D000818:Animals; D001152:Arsenicals / Q000627:therapeutic use; D004133:Diminazene / Q000627:therapeutic use; D004351:Drug Resistance / Q000235:genetics; D005838:Genotype; D008549:Melarsoprol / Q000627:therapeutic use*; D051379:Mice; D009547:Nifurtimox / Q000627:therapeutic use; D033703:Nucleoside Transport Proteins / Q000235:genetics; D021261:Parasitic Sensitivity Tests; D010419:Pentamidine / Q000627:therapeutic use; D010641:Phenotype; D016133:Polymerase Chain Reaction; D013397:Sudan; D017211:Treatment Failure; D014344:Trypanocidal Agents / Q000627:therapeutic use*; D014347:Trypanosoma brucei gambiense / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D014353:Trypanosomiasis, African / Q000188:drug therapy* / Q000469:parasitology
chemical_list: D001152:Arsenicals; D033703:Nucleoside Transport Proteins; C486446:P2 transporter, Trypanosoma brucei; D014344:Trypanocidal Agents; C044719:melarsen oxide; D010419:Pentamidine; D009547:Nifurtimox; D004133:Diminazene; D008549:Melarsoprol