Molecular typing of the actin gene of Trichomonas vaginalis isolates by PCR–restriction fragment length polymorphism

ABSTRACTHuman trichomoniasis, caused by the protozoan Trichomonas vaginalis, is a highly prevalent sexually transmitted infection. However, little is known about the degree of strain variability of T. vaginalis. A reliable classification method for T. vaginalis strains would be a useful tool in the study of the epidemiology, pathogenesis and transmission of T. vaginalis. A PCR–restriction fragment length polymorphism typing method was designed and evaluated using T. vaginalis isolates obtained after culture of vaginal specimens collected in the Democratic Republic of Congo and in Zambia. The variation of the actin gene of T. vaginalis was determined for three ATCC reference strains and 151 T. vaginalis isolates. Eight different types were identified, on the basis of the digestion patterns of the amplified actin gene, with each of the restriction enzymes HindII, MseI and RsaI. It was determined that the ATCC reference strains 30001, 30240 and 50141 were of actin genotypes G, H and E, respectively. The actin genotype type E was more common in the Democratic Republic of Congo, whereas type G was the commonest type in Zambia. Translation of the nucleotide sequence showed up to three amino acid substitutions. We developed a reproducible, sensitive and specific typing method for T. vaginalis, and were able to distinguish at least eight T. vaginalis actin genotypes. Further studies are needed to evaluate the method using clinical specimens and to determine the utility of the typing method for the genotypic characterization of T. vaginalis