Vaginal Infections -- How to Diagnose and Treat Them Appropriately

Sara M. Mariani, MD, PhD


November 18, 2003

In This Article


Approximately 3 million women in the United States are infected every year by T vaginalis. Of note, up to 50% of infections may be asymptomatic. Prevalence of infection has been estimated in some studies to be as high as 9% to 22% in pregnant women seen at inner-city clinics for sexually transmitted diseases (STDs). This compares, for instance, with a 17% prevalence rate of HIV infections in the same population. The risk of infection increases with other STDs and with multiple partners. Mixed infections are believed to occur in approximately 25% of cases. Hence, testing for T vaginalis should be offered together with testing for other STDs, such as Chlamydia, gonorrhea, etc.

Most importantly, 2% to 17% of children born from infected mothers are infected -- hence the necessity of appropriate prevention and early-diagnosis strategies in high-risk pregnant women.[2,5,8]

Prevalence of T vaginalis infection in men is not known, as the vast majority are asymptomatic; reports point to a 6% to 17% rate in men seen at STD clinics.[9,10,11] Of note, however, up to 66% of inmates and up to 58% of high-risk adolescents can test positive for T vaginalis infection.

T vaginalis is a protozoan mobile parasite, not part of the normal vaginal flora, with a pear-shaped appearance. It measures about 10 x 7 microns, and it can attach to epithelial cells through specific adhesion molecules.[12] If symptomatic, infection can be associated with irritation and a copious, yellow-green, frothy discharge. In about 5% to 12% of affected women, it may be accompanied by dysuria and abdominal discomfort. At local exam, inflammation of the vaginal walls may detectable, alongside a "strawberry" cervix in the acute forms. Chronic forms are associated with milder symptoms (mild pruritus, dyspareunia), but they represent a major source of transmission.

Conventionally, diagnosis of T vaginalis infection can be made with wet-mounts or stained preparations (Gram, Giemsa). Sensitivity at 50% to 80% can, however, be quite low. Cytologic detection in stained specimens (Giemsa, PAP) yields only a 60% to 70% sensitivity.

Cultures in Diamond's media yield better results with an overall sensitivity of about 85% to 95%, but they are more labor intensive and require long-term cultures (7 days). The use of plastic envelopes media (PEM) (containing tioconazole to suppress yeast growth)[13] and pouches[14] has simplified processing and yielded similar results. In a study by Beverly and colleagues,[15]T vaginalis obtained from swabs survived for 15 to 20 minutes, yielding a sensitivity of about 94% if inoculated in the pouches at the bedside and 91% when planted in the laboratory. Specificity for all assays is generally 100%.[1]

Molecular probes have now become available for the diagnosis of T vaginalis infections, which are useful to detect, concomitantly, the presence of C albicans. These amplification assays are very sensitive compared with cultures, but, unfortunately, also very expensive.[11,16,17]

Can urine be used for the detection of T vaginalis? In a study published by Blake and colleagues,[18] 97 of 686 (14%) 13- to 22-year-old girls tested positive by microscopic exam of vaginal cultures. When vaginal and urine specimen from a subset of 75 subjects were combined, sensitivity of detection by microscopic exam improved: from a rate of 64% using urine and 73% using vaginal fluid analysis to an 85% positive rate with mixed vaginal + urine specimens.

Candida Albicans Infections

Vulvovaginitis by C albicans are more frequent -- approximately 13 million cases are estimated to occur annually. At least 75% of women have had at least 1 episode in their lives, and 40% to 50% have at least 2 episodes. Recurring events occur in approximately 5% of women in the general population.[2] Clinically, infection is associated with vulvar irritation, dysuria, and a white ("cheesy") discharge. Risk factors for vaginal candidiasis include pregnancy, use of oral contraceptives, estrogen therapy, end of menstrual cycle, diabetes, and antibiotic therapy.[19,20,21]

Infection by C albicans can be diagnosed using wet mounts (although with a fairly low sensitivity of about 50%) or by culture. Sensitivity of isolation by culture is far higher when samples are obtained from a patient with an acute infection (95%) rather than from patients with chronic forms (68%). Molecular probes, developed more recently, yield a sensitivity comparable to that of cultures.[2]


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