JCM Accepts, published online ahead of print on 4 November 2009

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J. Clin. Microbiol. doi:10.1128/JCM.01449-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Longitudinal survey of Plasmodium falciparum infection in Vietnam: Characteristics of antimalarial resistance and their reflecting factors.

Rie Isozumi, Haruki Uemura^*, Le Duc Dao, Truong Van Hanh, Nguyen Duc Giang, Ha Viet Vien, Bui Quang Phuc, Nguyen Van Tuan, and Shusuke Nakazawa

Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam

^* To whom correspondence should be addressed. Email: uemura{at}nagasaki-u.ac.jp.

Plasmodium falciparum (P. falciparum) is responsible for the main cause of human malaria and one of the important pathogens related to high morbidity and mortality. The total number of malaria patients in Vietnam has gradually decreased over the last decade. However, the spread of pathogens with drug resistance remains a significant problem. Defining the trend in genotypes related to drug resistance is essential for malaria control in Vietnam.

We undertook a longitudinal survey of Plasmodium falciparum malaria during 2001-2002 and 2005-2007. The pfcrt, pfmdr1, pfdhfr and pfdhps genes were analyzed by sequencing, and correlations among study year, age, gender and genotype were identified statistically. The ratio of chloroquine resistant genotype pfcrt76T was found to have decreased rapidly subsequent to 2002. A high number of mutations in the pfdhfr and pfdhps genes were only observed in 2001-2002, while the emergence of the parasites with a new K540Y mutation in P. falciparum dihydropteroate synthetase (PfDHPS) was observed in 2002. Males and those in the younger age brackets demonstrated a correlation with vulnerability of malaria infection and the strain with pfcrt76K or that with decreased number of mutations in pfdhfr and pfdhps. The parasites with pfcrt76T exhibited a greater number of mutations in pfdhfr and pfdhps.