Population Genetics, Characterization of Virulence Factors, and Epidemiology in the Sexually Transmitted Parasite, Trichomonas vaginalis

Trichomonas vaginalis is a protozoan parasite that infects the urogenital tract of humans, causing trichomoniasis, the most common non-viral, sexually transmitted disease in the world. The symptoms of T. vaginalis infection include vaginitis and cervicitis in women and urethritis in men, although asymptomatic infection does occur. Trichomonas infection is associated with other infectious diseases and adverse pregnancy outcomes. In both sexes, T. vaginalis infection is a risk factor for HIV acquisition. Trichomonas infection is also associated with cervical neoplasia and prostate cancer in women and men, respectively.;Trichomonas prevalence is ten times higher in African American women than in Caucasian women, displaying a significant racial disparity. Likewise, HIV infection rates and adverse pregnancy outcomes are higher in African American women. Despite the health consequences of trichomoniasis and its disparate effects on health in the African American community, study of racial disparities in infected populations, genetic and phenotypic characterization of Trichomonas isolates and drug resistance in T. vaginalis is minimal. It is well established that associations between pathogen genotype and phenotypic manifestations, such as virulence, exist in many infectious diseases. A few small scale studies have also found associations between genotype and some phenotypic characteristics of T. vaginalis. However, conclusions vary, in part due to inconsistencies in the methods used for genetic characterization. We propose to use a new, more precise genotyping method to study the relationship between the genetics of T. vaginalis isolates, epidemiology, and the clinical manifestations of trichomoniasis. We hypothesized that the epidemiological differences and varied phenotypic manifestations displayed by T. vaginalis isolates are correlated with their genotypic strain genotype..;Three aims were put forth to test the above stated hypothesis: I. Development a consistent, portable, precise genotyping method that is suitable for and provides a sufficient level of discrimination power for distinguishing Trichomonas vaginalis strains. II. Characterization of metronidazole susceptibility of local clinical isolates and variations in virulence by measuring activity of the secreted cysteine protease (CP) CP30, a key virulence factor of T. vaginalis. III. Statistically measure the associations between genotype, epidemiology, and phenotypic manifestations of Trichomonas infection among the clinical isolates tested.;In this study, we introduced a multilocus sequence typing (MLST) scheme, comprised of seven single-copy housekeeping genes, to genetically characterize Trichomonas vaginalis. Initial characterization of 68 isolates, using MLST, revealed a genetically diverse T. vaginalis population with 60 sequence types distinguished among the 68 isolates. Linkage disequilibrium, recombination, and phylogenetic analyses determined that T. vaginalis has a population structure composed of two separate population clusters that may be in linkage equilibrium. There is currently no "gold standard" method for genetic characterization of T. vaginalis, and the use of MLST will provide a portable, precise, and unambiguous method for this purpose.;In vitro characterization of metronidazole susceptibility and secreted cysteine proteinase activity of T. vaginalis isolates revealed the extensive variation in virulence present in this species. The rate of in vitro metronidazole resistance in local isolates was found to be 8.2%, which is slightly higher than the nation average reported by the CDC. We found that isolates from asymptomatic cases have more secreted cysteine proteinase activity than isolates from symptomatic cases; an observation that is in direct contrast to surface associated cysteine proteinase in relation to symptomology. We also show that metronidazole resistant isolates secreted, on average, significantly less CP than metronidazole sensitive isolates; therefore demonstrating an inverse relationship between these two virulence factors.;Finally, our studies revealed distinct differences in the pathological manifestations of the two types of T. vaginalis. This suggests that genotype of T. vaginalis may be associated with clinical outcome. Completion of this study has produced an extensive catalog of well annotated T. vaginalis isolates with well-defined clinical and epidemiological descriptors. The techniques developed and results obtained from this study may serve as tools to investigate evolution, population structure, association mapping, and short- & long term epidemiology of T. vaginalis..