Inclusion Criteria:

• * Premenopausal individuals, 18- 40 years old
• * BV by Amsel criteria (at least 3 of 4 criteria must be present)
• * Abnormal Nugent score: ≥ 7
• * Willing and able to provide written informed consent.
• * HIV uninfected (by HIV Ab/Ag test at enrollment)
• * Not pregnant by pregnancy test at enrollment, and unlikely to have an early pregnancy per clinician's assessment of last menstrual period and recent sexual activity.
• * On continuous oral contraceptives (US site) or injectable progestin contraceptives (South African site) that suppress menstrual cycles, or willing to suppress menstrual cycles with one of these types of hormonal contraceptives
• * Willing and able to attend study visits and comply with study procedures

Exclusion Criteria:

• * History of clinically significant vaginal, cervical, or uterine disease including but not limited to: cancer of the female reproductive tract
• * Prior hysterectomy
• * Diagnosed with cervicovaginal infection (inclusive of gonorrhoeae, chlamydia, trichomonas) within the 30 days prior (or at enrollment visit). Yeast and bacterial vaginosis are not exclusionary.
• * Use of antibiotics in the past 30 days
• * Syphilis (positive screen at enrollment)
• * Vulvovaginal candidiasis (positive microscopy at enrollment)
• * Allergy to or contraindication to use of oral metronidazole
• * High grade abnormal Pap (HSIL, AGC \[Atypical Glandular Cells\], ASCUS-H) at enrollment (LSIL, ASCUS, or HPV+ are all non-exclusionary)
• * Currently participating in another study of an investigational product (excluding COVID vaccine studies)
• * Use of long-acting systemic investigational product (e.g. injectable PrEP) within the past year
• * Subject taking any of the following medications currently or in the past 30 days: systemic steroids (inhaled or nasal steroid therapy is permitted), interleukins, systemic interferons (e.g. local injection of interferon alpha for treatment of human papillomavirus is permitted) or systemic chemotherapy.
• * History of coronary artery disease, myocardial infarction, chronic obstructive pulmonary disease, chronic renal failure, decompensated cirrhosis, or any other condition that in the opinion of the investigator will compromise ability to participate in the study.
• * Use of an IUD (intrauterine device)
• * Use of probiotics, prebiotics or synbiotics (supplements and products, oral or vaginal) within past 30 days. (NOTE: Oral yogurt with live cultures is allowed, as are fermented foods.)
• * Active COVID-19 infection (determined by a positive PCR test of a nasal or nasopharyngeal swab) or recent exposure (\< 14 days) to someone with confirmed COVID-19 infection (an exposure is considered being within 6 feet/180 cm of someone without a mask for more than 15 minutes). Potential participants who meet these criteria can delay screening until they have completed isolation or quarantine.
• * Vaginal cleansing practices in the past 30 days (i.e. vaginal products for cleaning or drying, vaginal douching) (by eligibility questionnaire)
• * Any other condition or situation that in the opinion of the investigator will compromise ability to participate in the study.
• * Menopause: surgical; or absence of periods not due to hormonal contraception and in the setting of prior chemotherapy
• * Use of testosterone for any reason
• * Systolic blood pressure \> 180 or diastolic blood pressure \> 110 at screening or enrollment
• * Hemoglobin \< 9
• * Less than 2 weeks since 2nd COVID vaccination (mRNA) or 1st vaccination (J\&J) or booster
• * Either breastfeeding/lactating or pregnant within 8 weeks prior to study entry