Molecular epidemiology of metronidazole resistance in a population of Trichomonas vaginalis clinical isolates

Trichomonas vaginalis, the causative agent for human trichomoniasis, is a p roblematic sexually transmitted disease mainly in women, where it may be as ymptomatic or cause severe vaginitis and cervicitis. Despite its high preva lence, the genetic variability and drug resistance characteristics of this organism are poorly understood. To address these issues, genetic analyses w ere performed on 109 clinical isolates using three approaches, First, two i nternal transcribed spacer (ITS) regions flanking the 5.8S subunit of the r ibosomal DNA gene were sequenced. The only variation was a point mutation a t nucleotide position 66 of the ITS1 region found in 16 isolates (14.7%), S econd, the presence of a 5.5-kb double-stranded RNA T, vaginalis virus (TVV ) was assessed. TW was detected in 55 isolates (50%), Finally, a phylogenet ic analysis was performed based on random amplified polymorphic DNA data, T he resulting phylogeny indicated at Least two distinct lineages that correl ate with the presence of TW, A band-sharing index indicating relatedness wa s created for different groups of isolates. It demonstrated that isolates h arboring the virus are significantly more closely related to each other tha n to the rest of the population, and it indicated a high level of relatedne ss among isolates with in vitro metronidazole resistance. This finding is c onsistent with the hypothesis that drug resistance to T, vaginalis resulted from a single or very few mutational events. Permutation tests and nonpara metric analyses showed associations between metronidazole resistance and ph ylogeny, the ITS mutation, and TVV presence. These results suggest the exis tence of genetic markers with clinical implications for T, vaginalis infect ions.