Johns Hopkins University School of Medicine, Broadway Research Building,733 N. Broadway, Suite 147, Baltimore, MD 21205, USA.
Malar J. 2012 Sep 19;11:333. doi: 10.1186/1475-2875-11-333.
Confirmation of artemisinin-delayed parasite clearance in Plasmodium falciparum along the Thai-Myanmar border has inspired a global response to contain and monitor drug resistance to avert the disastrous consequences of a potential spread to Africa. However, resistance data from Myanmar are sparse, particularly from high-risk areas where limited health services and decades of displacement create conditions for resistance to spread. Subclinical infections may represent an important reservoir for resistance genes that confer a fitness disadvantage relative to wild-type alleles. This study estimates the prevalence of resistance genotypes in three previously unstudied remote populations in Myanmar and tests the a priori hypothesis that resistance gene prevalence would be higher among isolates collected from subclinical infections than isolates collected from febrile clinical patients. A systematic review of resistance studies is provided for context.
Community health workers in Karen and Kachin States and an area spanning the Indo-Myanmar border collected dried blood spots from 988 febrile clinical patients and 4,591 villagers with subclinical infection participating in routine prevalence surveys. Samples positive for P. falciparum 18 s ribosomal RNA by real-time PCR were genotyped for P. falciparum multidrug resistance protein (pfmdr1) copy number and the pfcrt K76T polymorphism using multiplex real-time PCR.
Pfmdr1 copy number increase and the pfcrt K76 polymorphism were determined for 173 and 269 isolates, respectively. Mean pfmdr1 copy number was 1.2 (range: 0.7 to 3.7). Pfmdr1 copy number increase was present in 17.5%, 9.6% and 11.1% of isolates from Karen and Kachin States and the Indo-Myanmar border, respectively. Pfmdr1 amplification was more prevalent in subclinical isolates (20.3%) than clinical isolates (6.4%, odds ratio 3.7, 95% confidence interval 1.1 - 12.5). Pfcrt K76T prevalence ranged from 90-100%.
Community health workers can contribute to molecular surveillance of drug resistance in remote areas of Myanmar. Marginal and displaced populations under-represented among previous resistance investigations can and should be included in resistance surveillance efforts, particularly once genetic markers of artemisinin-delayed parasite clearance are identified. Subclinical infections may contribute to the epidemiology of drug resistance, but determination of gene amplification from desiccated filter samples requires further validation when DNA concentration is low.
在泰缅边境确认青蒿素延迟寄生虫清除后，全球采取行动遏制和监测抗药性，以避免这种潜在的耐药性传播到非洲所带来的灾难性后果。然而，来自缅甸的耐药性数据很少，特别是在高危地区，那里有限的卫生服务和几十年的流离失所导致耐药性传播的条件。亚临床感染可能代表着对野生型等位基因具有适应性劣势的耐药基因的重要储存库。本研究估计了缅甸三个以前未研究的偏远地区的耐药基因型的流行率，并检验了一个先验假设，即从亚临床感染中分离出的耐药基因的流行率将高于从发热临床患者中分离出的耐药基因。提供了耐药性研究的系统评价作为背景。
在克伦邦和克钦邦以及跨越印缅边境的一个地区，社区卫生工作者从 988 名发热临床患者和 4591 名患有亚临床感染的村民中采集了干燥血斑。通过实时 PCR 检测到对疟原虫 18 s 核糖体 RNA 呈阳性的样本使用多重实时 PCR 对疟原虫多药耐药蛋白 (pfmdr1) 拷贝数和 pfcrt K76T 多态性进行基因分型。
确定了 173 个和 269 个分离株的 pfmdr1 拷贝数增加和 pfcrt K76 多态性。平均 pfmdr1 拷贝数为 1.2（范围：0.7 至 3.7）。分别来自克伦邦和克钦邦以及印缅边境的分离株中 pfmdr1 拷贝数增加的比例为 17.5%、9.6%和 11.1%。亚临床分离株中 pfmdr1 扩增更为普遍（20.3%），而临床分离株中 pfmdr1 扩增较少（6.4%，比值比为 3.7，95%置信区间为 1.1-12.5）。pfcrt K76T 的流行率为 90-100%。
社区卫生工作者可以为缅甸偏远地区的耐药性分子监测做出贡献。在以前的耐药性调查中代表性不足的边缘和流离失所人群，应该包括在耐药性监测工作中，特别是一旦确定了青蒿素延迟寄生虫清除的遗传标记。亚临床感染可能会影响耐药性的流行病学，但在 DNA 浓度较低时，从干燥滤器样本中确定基因扩增需要进一步验证。
