Inclusion Criteria:
* Premenopausal women, 18- 50 years old
* Abnormal Nugent score: \> 3
* History of recurrent bacterial vaginosis (BV) (3 or more documented episodes in past 12 months)
* If participating in sexual activity that could lead to pregnancy, study participants must agree to use an effective contraceptive while actively participating in the protocol. At least one of the following methods MUST be used:
* Condoms (male or female), with or without a spermicidal agent
* Intrauterine device (IUD)
* Hormonal contraceptive (including oral pills, vaginal ring, implant, injection)
Exclusion Criteria:
* History of clinically significant vaginal, cervical, or uterine disease including but not limited to: cancer of the female reproductive tract, prior hysterectomy, high grade cervical dysplasia (CIN III), or diagnosed with cervicovaginal infection (with the exception of bacterial vaginosis) within the 30 days prior to the procedure.
* Allergy to metronidazole
* Use of investigational therapies or investigational vaccines within 90 days prior to study entry
* Use of any immunomodulatory agents within 30 days prior to study enrollment. Subject taking any of the following medications: systemic steroids (inhaled or nasal steroid therapy is permitted), interleukins, systemic interferons (e.g. local injection of interferon alpha for treatment of HPV is permitted) or systemic chemotherapy.
* History of coronary artery disease, myocardial infarction, COPD, chronic renal failure, decompensated cirrhosis, or any other condition that in the opinion of the investigator will compromise ability to participate in the study.
* History of abnormal pap smear within 12 months
* Insertion of levonorgestrel-containing IUD within 3 months prior to study entry
* Either breastfeeding or pregnant within 24 weeks prior to study entry
* Use of probiotics and prebiotics (supplements and products, oral or vaginal) within 30 days of the study. (NOTE: Oral yogurt with live cultures is allowed.)
* Routine use of oral antibiotics i.e. daily use for acne, Hidradenitis suppurativa, or regular use for post-coital urinary tract infection prophylaxis within the past 30 days.
* Taken non-metronidazole antibiotics in last 30 days
* BMI \> 40
