How Common are Co-infections with Trichomonas and Bacterial Vaginosis?

Patient Presentation
A 16-year-old female came to adolescent clinic with a 2 day history of foul-smelling vaginal discharge and vulvar irritation. The discharge amount was increasing. The color was “whitish” and the consistency she couldn’t describe. She had a new male sexual partner for the past week. She used Depo-Provera┬« for birth control and usually used condoms as well, but had not with the new partner. The last sexual contact was 2 days before the increasing discharge. She denied any new soaps, lotions or personal hygiene products or new laundry products. She usually wore tight fitting pants consistent with the current style. She had no fever, chills, nausea, emesis, and urinary changes. Her last menses was 18 days ago. The past medical history showed she had been tested for sexually transmitted infections (STI) including HIV.

The pertinent physical exam showed a healthy female with normal vital signs. Her abdominal examination was negative. Her external genitourinary examination showed general irritation of the vulva and perineum. There was a thin discharge at the introitus. She declined speculum examination.

The laboratory evaluation included a wet prep that was positive for whiff test, vaginal pH = 5.0 and showed clue cells. No protozoa were seen. She agreed to testing for Neisseria and Chlamydia as well and these were eventually negative. The diagnosis of bacterial vaginosis and possible trichomonas was made. She was treated with metronidazole and counseled about use of condoms and other STI prevention measures including contacting her new partner. She was to followup within 2-3 months.

Vulvovaginitis is a common gynecological complaint for females of all ages. It is specifically the inflammation of the vulva and vagina but is used as a general term often to mean vulvar irritation, itching, and burning that can occur with or without vaginal discharge. In prepubertal females there is lack of estrogenization, and less lactobacillus species which creates a more neutral pH (normal vaginal pH is < 4.5), lack of pubic hair and fat pad which provide trauma protection, location of anus close to the vagina and tendency of poor hygiene in young children. With puberty, estrogen thickens the vaginal tissues and more lactobacillus species lowers the vaginal pH which makes a more hostile environment for other infections.

The differential diagnosis of vulvovaginitis changes depending on the pubertal status and can be reviewed here.

Learning Point
Bacterial vaginosis (BV) is one of the most common causes of vaginal discharge and irritation in adolescents and adult women. In adolescents prevalence is > 20%. BV is caused by a change in the normal vaginal flora with a decrease in lactobacillus and an overgrowth of facultative anaerobic organisms. These organisms include Garnerella vaginalis, Atopobium vaginae, Bacteroides species, Fusobacterium species, Mycoplasma hominis, Peptostreptococcus, Ureaplasma species and others. Studies suggest that with the increased vaginal pH, Gardnerella more easily adheres to the vaginal epithelium creating a biofilm which also may increase the risk of other STIs to occur if exposed. BV is not a specific STI but occurs more often in sexually active people. The risks of BV increase after puberty, with new or multiple sexual partners, lack of condom use, douching or absence of lactobacilli. BV presents as a thin, whitish-grey vaginal discharge that usually has a “fishy” odor. Diagnosis is made with 3 of 4 criteria which include presence of characteristic discharge, positive amine “whiff” test which smells like fish with the addition of potassium hydroxide (KOH) to a vaginal wet prep, vaginal pH > 4.5 (normal 3.8-4.5) and > 20% clue cells (i.e. vaginal epithelia cells that have a stippled appearance because of adherent bacteria). Gram stain is considered the gold standard for diagnosis and various commercial testing is available. Depending on practice location commercial testing may be easier to perform. Untreated BV is associated with preterm labor, irregular menstrual bleeding and pelvic inflammatory disease. Treatment is usually with metronidazole orally or vaginally with clindamycin (orally or vaginally) or tinidazole orally as alternatives.

Trichomonas vaginalis (Trich) is also a common infection for adolescent females. It is the most common non-viral STI. Protozoa infect genital squamous epithelial cells from contaminated genital secretions and is considered an STI. Co-infection with BV is very common and reported to be up to 60-80%. Trich is often asymptomatic (70-85%) but may present as a malodorous, frothy profuse discharge with irritation and pruritis. Like BV, vaginal pH is > 4.5 and on speculum exam small cervical hemorrhages create the “strawberry cervix” appearance. Vaginal wet preparation may show motile protozoa but a negative wet prep does not rule out the infection. Untreated trich can progress to urethritis or cystitis, and in pregnant women is associated with preterm delivery. Treatment is with metronidazole or tinidazole with sexual partners also treated.

Questions for Further Discussion
1. What STIs need to be reported to public health in your area?
2. How common is pelvic inflammatory disease and what are common organisms that cause it?
3. What other health problems are caused by changes in the biome or creation of a biofilm?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Vaginitis and Vulvar Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Tamburini S, Shen N, Wu HC, Clemente JC. The microbiome in early life: implications for health outcomes. Nat Med. 2016;22(7):713-722. doi:10.1038/nm.4142

Loveless M, Myint O. Vulvovaginitis- presentation of more common problems in pediatric and adolescent gynecology. Best Pract Res Clin Obstet Gynaecol. 2018;48:14-27. doi:10.1016/j.bpobgyn.2017.08.014

Lanis A, Talib HJ, Dodson N. Prepubertal and Adolescent Vulvovaginitis: What to Do When a Girl Reports Vaginal Discharge. Pediatr Ann. 2020;49(4):e170-e175. doi:10.3928/19382359-20200317-01

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa