A 20-year-old female presents with complaints of vaginal itching and irritation for the past three days. Two weeks ago, she had streptococcal pharyngitis and was treated with amoxicillin. For the last year, she has had one male sex partner and she reports that they consistently use condoms. Pelvic examination reveals erythema of the vulva and vagina and the presence of a thick, whitish vaginal discharge. The pH of the discharge is 4.0.