Which of the following sexually transmitted diseases is caused by a protozoal infection?

A. Chlamydia. This infection is caused by Chlamydia trachomatis, which is a gram-negative bacterium. It is an obligate intracellular pathogen requiring a host cell to replicate. Bacterial infections are treated with antibiotics like azithromycin or doxycycline rather than antiprotozoal agents. B. Syphilis. The causative agent is Treponema pallidum, a motile spirochete bacterium. It progresses through primary, secondary, and tertiary stages if left untreated by penicillin. Spirochetes are distinct from protozoa in their cellular structure, metabolic processes, and classification as bacteria. C. Trichomoniasis. This condition is caused by Trichomonas vaginalis, a flagellated protozoan parasite. It primarily infects the squamous epithelium of the urogenital tract in both males and females. As a single-celled eukaryote, it requires specific anaerobic treatment with nitroimidazoles like metronidazole. D. Gonorrhea. This sexually transmitted infection results from Neisseria gonorrhoeae, a pyogenic diplococcus bacterium. It targets mucous membranes of the reproductive tract, mouth, and rectum. Management involves dual antibiotic therapy to address potential resistance, confirming its classification as a bacterial rather than protozoal disease.