Melissa D Conrad

CUNY Graduate Center, New York City, New York, United States

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Publications (5)19.37 Total impact

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    ABSTRACT: OBJECTIVES: Recently developed genotyping tools allow better understanding of Trichomonas vaginalis population genetics and epidemiology. These tools have yet to be applied to T vaginalis collected from HIV(+) populations, where understanding the interaction between the pathogens is of great importance due to the correlation between T vaginalis infection and HIV transmission. The objectives of the study were twofold: first, to compare the genetic diversity and population structure of T vaginalis collected from HIV(+) women with parasites from reference populations; second, to use the genetic markers to perform a case study demonstrating the usefulness of these techniques in investigating the mechanisms of repeat infections. METHODS: Repository T vaginalis samples from a previously described treatment trial were genotyped at 11 microsatellite loci. Estimates of genetic diversity and population structure were determined using standard techniques and compared with previously reported estimates of global populations. Genotyping data were used in conjunction with behavioural data to evaluate mechanisms of repeat infections. RESULTS: T vaginalis from HIV(+) women maintain many of the population genetic characteristics of parasites from global reference populations. Although there is evidence of reduced diversity and bias towards type 1 parasites in the HIV(+) population, the populations share a two-type population structure and parasite haplotypes. Genotyping/behavioural data suggest that 36% (12/33) of repeat infections in HIV(+) women can be attributed to treatment failure. CONCLUSIONS: T vaginalis infecting HIV(+) women is not genetically distinct from T vaginalis infecting reference populations. Information from genotyping can be valuable for understanding mechanisms of repeat infections.
    Sexually transmitted infections 05/2013; · 2.18 Impact Factor
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    ABSTRACT: Trichomonas vaginalis is a parasite of the urogenital tract in men and women, with a worldwide presence and significant implications for global public health. T. vaginalis research entered the age of genomics with the publication of the first genome sequence in 2007, but subsequent utilization of other 'omics' technologies and methods has been slow. Here, we review some of the tools and approaches available to interrogate T. vaginalis biology, with an emphasis on recent advances and current limitations, and draw attention to areas where further efforts are needed to examine effectively the complex and intriguing biology of the parasite.
    Trends in Parasitology 12/2012; · 5.51 Impact Factor
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    ABSTRACT: Trichomonas vaginalis is the causative agent of human trichomoniasis, the most common non-viral sexually transmitted infection world-wide. Despite its prevalence, little is known about the genetic diversity and population structure of this haploid parasite due to the lack of appropriate tools. The development of a panel of microsatellite makers and SNPs from mining the parasite's genome sequence has paved the way to a global analysis of the genetic structure of the pathogen and association with clinical phenotypes. Here we utilize a panel of T. vaginalis-specific genetic markers to genotype 235 isolates from Mexico, Chile, India, Australia, Papua New Guinea, Italy, Africa and the United States, including 19 clinical isolates recently collected from 270 women attending New York City sexually transmitted disease clinics. Using population genetic analysis, we show that T. vaginalis is a genetically diverse parasite with a unique population structure consisting of two types present in equal proportions world-wide. Parasites belonging to the two types (type 1 and type 2) differ significantly in the rate at which they harbor the T. vaginalis virus, a dsRNA virus implicated in parasite pathogenesis, and in their sensitivity to the widely-used drug, metronidazole. We also uncover evidence of genetic exchange, indicating a sexual life-cycle of the parasite despite an absence of morphologically-distinct sexual stages. Our study represents the first robust and comprehensive evaluation of global T. vaginalis genetic diversity and population structure. Our identification of a unique two-type structure, and the clinically relevant phenotypes associated with them, provides a new dimension for understanding T. vaginalis pathogenesis. In addition, our demonstration of the possibility of genetic exchange in the parasite has important implications for genetic research and control of the disease.
    PLoS Neglected Tropical Diseases 03/2012; 6(3):e1573. · 4.57 Impact Factor
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    ABSTRACT: The following series of concise summaries addresses the evolution of infectious agents in relation to sex in animals and humans from the perspective of three specific questions: (1) what have we learned about the likely origin and phylogeny, up to the establishment of the infectious agent in the genital econiche, including the relative frequency of its sexual transmission; (2) what further research is needed to provide additional knowledge on some of these evolutionary aspects; and (3) what evolutionary considerations might aid in providing novel approaches to the more practical clinical and public health issues facing us currently and in the future?
    Annals of the New York Academy of Sciences 08/2011; 1230:74-107. · 4.38 Impact Factor
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    ABSTRACT: Given the growing appreciation of serious health sequelae from widespread Trichomonas vaginalis infection, new tools are needed to study the parasite's genetic diversity. To this end we have identified and characterized a panel of 21 microsatellites and six single-copy genes from the T. vaginalis genome, using seven laboratory strains of diverse origin. We have (1) adapted our microsatellite typing method to incorporate affordable fluorescent labeling, (2) determined that the microsatellite loci remain stable in parasites continuously cultured for up to 17 months, and (3) evaluated microsatellite marker coverage of the six chromosomes that comprise the T. vaginalis genome, using fluorescent in situ hybridization (FISH). We have used the markers to show that T. vaginalis is a genetically diverse parasite in a population of commonly used laboratory strains. In addition, we have used phylogenetic methods to infer evolutionary relationships from our markers in order to validate their utility in future population analyses. Our panel is the first series of robust polymorphic genetic markers for T. vaginalis that can be used to classify and monitor lab strains, as well as provide a means to measure the genetic diversity and population structure of extant and future T. vaginalis isolates.
    Molecular and Biochemical Parasitology 01/2011; 175(1):30-8. · 2.73 Impact Factor