Abstract: Objective To type clinical strains of C.trachomatis by sequence analysis of VS1-VS2 region of omp1 gene,and to investigate the mutation rate of this gene.Methods Urogenital specimens were collected from 99 patients attending our STD clinic.The VS1-VS2 region of omp1 gene was amplified in these specimens by nested PCR,and sequenced with an automatic sequencer.The sequencing results were blasted against sequences of reference strains by DNAstar software.Results A 435-bp fragment of VS1-VS2 region was amplified from all 99 clinical samples.Three specimens appeared to contain multiple pathogens and could not be genotyped.The remaining 96 strains were classified into 9 genotypes.The most prevalent types in decreasing order were F(29,30.2%),E(22,22.9%),J(19,19.8%),D(12, 12.5%)and H(8,8.3%).Seven(7.3%)strains showed base mutation or insertion in VS1 region,most of which were sense mutation and primarily occurred among genotypes D,E,F and H.Conclusion Sequencing analysis of omp1 gene may be useful in the molecular epidemiology of C.trachomatis infection.

Key words: Chlamydia trachomatis, Sequence analysis,DNA, Genotype, Mutation