Circulation of dengue serotypes in five provinces of northern Thailand during 2002-2006.

disease prevalent in all provinces of Thailand. This study was to determine the circulating dengue serotypes by reverse transcription polymerase chain reaction (RT-PCR). A total of 1116 seropositive acute samples were analysed from DF/DHF patients in five provinces of northern Thailand (Chiangmai, Lampang, Lamphun, Mae Hong Son and Phrae) during the period January 2002 to December 2006. Five hundred and fifty-nine samples were found positive, of which 47.2%, 30.6%, 18.4% and 3.8% were affected with DENV-2, DENV-1, DENV-4 and DENV-3 respectively. From 2002 to 2005, the predominant dengue serotype was DENV-2, whereas DENV-1 was predominant in 2006. There was an apparent increase in the percentage of DENV-4 from 2005 to 2006. Our results indicated that all four dengue serotypes were circulating in this region and the annual change of predominant serotypes was the cause of the severity of the disease.

Genotype distribution of genital Chlamydia trachomatis in Chiang Mai, Thailand.

Urogenital isolates (N=84) of Chlamydia trachomatis collected from high-risk STD subjects in Chiang Mai and the surrounding areas were investigated for genotype distribution. C. trachomatis genotypes were determined by the PCR-based RFLP technique and confirmed by nucleotide sequencing. By this method, the VD4 DNA of the MOMP gene was amplified and digested separately with 4 restriction endonucleases, AluI, HindIII, DdeI, and EcoRII. The nucleotide sequence was determined by dye terminator cycle sequencing. Eight different C. trachomatis genotypes were identified: genotype D (34.5%), F (21.4%), K (13.1%), H/Ia (8.3%), E (7.1%), B/Ba (7.1%), G (6.0%), and J (2.4%). Genotype D and F were the commonest, accounting for 56% of the C. trachomatis infections. When nucleotides of the VD4-MOMP gene were anlyzed, 43 samples (51.2%) had nucleotide sequences that differed from the prototypes, while 41 (48.8%) were identical. Nucleotide substitution mutation was the major mechanism in these variants; changes in nucleotide sequences usually resulted in amino acid substitution, which could lead to a modification of antigenic determinants and the consequent evasion of immune responses.