Observation of Probable Persistent, Undetected Trichomonas vaginalis Infection among HIV-Positive Women

Peterman et al. reported the possibility that after treatment, Trichomonas vaginalis (TV) infection can become nondetectable for months and then reappear 1. His study population consisted of women attending 3 clinics that specialized in the treatment of sexually transmitted diseases. The data included 13 women who had previously been infected with TV and treated, and subsequently 11 (85%) had an intervening negative test result before having a positive result when no sexual exposure was reported 1. This scenario suggests that TV infection remained undetectable by testing, which was done by culture using the InPouch TV test (BioMed Diagnostics), but the infection was still present for many months after treatment. Culture may only detect infections if the concentration of TV is higher than a certain level, and the organism concentration may take time to increase to detectable levels after treatment. Therefore, the most appropriate time to retest women for TV using culture remains unknown. We examined the possibility of persistent, undetected TV infections among HIV-infected women using data from our recent randomized treatment trial of TV 2. Participants (HIV+/TV+ women) were enrolled from selected HIV outpatient clinics in New Orleans, Louisiana; Houston, Texas; and Jackson, Mississippi; and were randomized to treatment arm: metronidazole 2 gm single dose or metronidazole 500mg twice a day for 7 days dose. TV was diagnosed by culture (InPouch TV test, Biomed Diagnostics) and women were retested for TV at a test-of-cure visit occurring 6-12 days after treatment, and at 3 and 6 months after enrollment. To examine persistent, undetected TV infections, we specifically looked at participants with a negative test result preceding a positive result (or repeat TV infection) when no sexual exposure to baseline or new partners was reported. At the 3 month visit, there were 26 women who tested positive for TV after having an intervening negative result (test-of-cure visit). Of these 26 women, 30.8% (n=8) reported no sexual exposure from the baseline visit to the 3 month visit. These 8 repeat infections were probably due to treatment failure, since the women reported adherence to treatment and no sexual exposure, but were not detected by culture at the test-of-cure visit. At the 6 month visit, there were 19 women who tested positive for TV after having at least one intervening negative result (test-of-cure and/or 3 month visit) and no intervening positive results since baseline. Of these 19 women, 21.1% (n=4) reported no sexual exposure from the baseline visit to the 6 month visit and were all adherent to treatment at baseline. It is possible that these 4 repeat infections still represent treatment failure, and remained nondetectable by culture for months and then reappeared. Our findings are consistent with the results from Peterman et al., and suggest that prospective studies are needed to assess the timeframe for culture detection of persistent TV infections. One approach may be to frequently test women after treatment for TV using both culture and PCR techniques to determine when the repeat infection reaches culture-detectable levels. It is important to prevent false-negative results, especially if women will not be returning for more testing, given the association between TV infection and HIV acquisition and transmission 3-6.