Autor/a:
|
Barnadas, Céline; Timinao, Lincoln; Javati, Sarah; Iga, Jonah; Malau, Elisheba; Koepfli, Cristian; Robinson, Leanne J.; Senn, Nicolas; Kiniboro, Benson; Rare, Lawrence; Reeder, John C.; Siba, Peter; Zimmerman, Peter A.; Karunajeewa, Harin; Davis, Timothy M.; Mueller, Ivo
|
Abstract:
|
BACKGROUND: Drug resistance remains a major obstacle to malaria
treatment and control. It can arise and spread rapidly, and vary
substantially even at sub-national level. National malaria
programmes require cost-effective and timely ways of
characterizing drug-resistance at multiple sites within their
countries. METHODS: An improved multiplexed post-PCR ligase
detection reaction-fluorescent microsphere assay (LDR-FMA) was
used to simultaneously determine the presence of mutations in
chloroquine resistance transporter (crt), multidrug resistance 1
(mdr1), dihydrofolate reductase (dhfr) and dihydropteroate
synthase (dhps) genes in Plasmodium falciparum (n = 727) and
Plasmodium vivax (n = 574) isolates collected in 2006 from
cross-sectional community population surveys in two
geographically distinct regions (Madang and East Sepik) of Papua
New Guinea (PNG) where strong regional differences in in vivo
aminoquinoline and antifolate therapeutic efficacy had
previously been observed. Data were compared to those of a
follow-up survey conducted in 2010. RESULTS: Despite some very
low parasite densities, the assay successfully amplified all P.
falciparum and P. vivax loci in 77 and 69 % of samples,
respectively. In 2006, prevalences of pfdhfr (59R-108 N) double
mutation/wild type pfdhps haplotype, pfcrt SVMNT haplotype
(72S-76T double mutation), and 86Y pfmdr1 mutation all exceeded
90 %. For P. vivax, 65 % carried at least two pvdhfr mutations,
97 % the 647P pvdhps mutation and 54 % the 976F pvmdr1 mutation.
Prevalence of mutant haplotypes was higher in Madang than East
Sepik for pfcrt SVMNT (97.4 vs 83.3 %, p = 0.001), pfdhfr
(59R-108 N) (100 vs 90.6 %, p = 0.001), pvdhfr haplotypes (75.8
vs 47.6 %, p = 0.001) and pvmdr1 976F (71.2 vs 26.2 %, p <
0.001). Data from a subsequent Madang survey in 2010 showed that
the prevalence of pfdhps mutations increased significantly from
<5 % to >30 % (p < 0.001) as did the prevalence of
pvdhfr mutant haplotypes (from 75.8 to 97.4 %, p = 0.012).
CONCLUSIONS: This LDR-FMA multiplex platform shows feasibility
for low-cost, high-throughput, rapid characterization of a broad
range of drug-resistance markers in low parasitaemia infections.
Significant geographical differences in mutation prevalence
correlate with previous genotyping surveys and in vivo trials
and may reflect variable drug pressure and differences in
health-care access in these two PNG populations. |