Trichomoniasis — DTM&H MCQ

Correct answer: C — Metronidazole with partner treatment

Metronidazole with partner treatment (option A) is correct because the clinical triad of frothy vaginal discharge, vulval irritation and a strawberry cervix, combined with motile flagellated protozoa on wet mount, is diagnostic of Trichomonas vaginalis. Nitroimidazoles (metronidazole or tinidazole) are the only drug class with reliable trichomonacidal activity, working by disrupting the anaerobic organism's electron transport chain after intracellular reduction. Because trichomoniasis is sexually transmitted and reinfection from an untreated partner is common, current UK guidance mandates concurrent partner notification and treatment, along with abstinence until both partners have completed therapy. Why the other options are wrong: D. Praziquantel: this is the treatment for schistosomiasis and other trematode or cestode infections; it has no activity against protozoal flagellates like Trichomonas. A. Cefalexin: a cephalosporin antibiotic active against bacterial pathogens, not protozoa; it would not touch a flagellated organism seen on wet mount. E. Doxycycline prophylaxis: doxycycline covers Chlamydia and some bacterial STIs but is ineffective against Trichomonas, and prophylactic dosing is not the management of an established symptomatic infection. B. Fluconazole cream: this is an antifungal used for vulvovaginal candidiasis, which typically causes thick curdy discharge without motile organisms on microscopy; it has no effect on protozoa. Key point: motile flagellates on wet mount with a strawberry cervix confirm Trichomonas vaginalis, which requires nitroimidazole therapy plus mandatory partner treatment to prevent reinfection.

Reference: BASHH, United Kingdom national guideline on the management of Trichomonas vaginalis (2021), British Association for Sexual Health and HIV, https://www.bashhguidelines.org/media/1224/tv-2021.pdf