Genetic typing of the 56-kDa type-specific antigen gene of contemporary Orientia tsutsugamushi isolates causing human scrub typhus at two sites in north-eastern and western Thailand.
Orientia tsutsugamushi is the causative agent of scrub typhus, a major cause of febrile illness in the rural areas of Southeast Asia. Twenty-three strains of O. tsutsugamushi were isolated from patients with scrub typhus in north-east (Udorn Thani province) and western Thailand (Tak province) between 2003 and 2005. The isolates were characterized by sequencing the entire ORF of the 56-kDa-type-specific antigen gene, followed by phylogenetic analysis. The majority (15/23) of isolates clustered with the Karp-type strain, six with a Gilliam-type strain and one each with the TA716- and TA763-type strains. Overall, there was considerable diversity in sequence, comparable to that seen in strains from across the rest of the scrub typhus-endemic world. There was no significant difference in the distributions of strains between the two provinces (P=0.08, Fisher's exact) nor a temporal change in distribution with year of isolation (P=0.80, Fisher's exact). Within this diversity there were also examples of isolates with identical 56-kDa genotypes that were cultured from patients from the same geographical areas.
Blacksell
Stuart D
SD
Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand. stuart@tropmedres.ac
Luksameetanasan
Rungnapa
R
Kalambaheti
Thareerat
T
Aukkanit
Nuntipa
N
Paris
Daniel H
DH
McGready
Rose
R
Nosten
François
F
Peacock
Sharon J
SJ
Day
Nicholas P J
NP
D000942:Antigens, Bacterial / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D012285:Orientia tsutsugamushi / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D012612:Scrub Typhus / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013785:Thailand / Q000453:epidemiology
D000942:Antigens, Bacterial; D004269:DNA, Bacterial