Vaginal Infections -- How to Diagnose and Treat Them Appropriately

Sara M. Mariani, MD, PhD


November 18, 2003

In This Article

Bacterial Vaginosis or Vaginal Bacteriosis

Differently from nonspecific vaginitis caused by Haemophilus vaginalis, Corynebacterium vaginale, G vaginalis, and anaerobic vaginitis caused by Mobilincus, BV is characterized by an "increased fluid flow" rather than inflammation of the vagina.[2,22] Hence some wonder whether it would not be more appropriate to define it vaginal bacteriosis.

BV is usually caused by a mixed flora, both aerobic and anaerobic. Prevalence is increased in sexually active women affected by other STDs or who have sex with multiple partners. It is quite contagious, as more than 80% of men are infected when the partner carries an infection. In some cases, however, it may not be a "true" STD as it can occur also in virgins, and G vaginalis can be isolated from the rectum, as well. Monif has suggested a classification in type I and II, where type II is sexually transmitted.[23]

Prevalence of BV is quite high among the general population: a prevalence of 17% to 19% has been reported from family planning clinics, and of 4% to 10% from student health clinics. It can be, however, as high as 24% to 40% in women seen at STD clinics.[2] Of note, prevalence in pregnant US women is in the range of 16% to 29%, and up to 30% of women visiting infertility clinics may be affected by BV.[22] Clinical manifestations include discomfort and pungent odor, a gray, thin, homogenous discharge, but rarely dysuria. Characteristically, signs of inflammation are not present in the vaginal walls, although a few leukocytes may be present.

What causes a BV? Oftentimes, it derives from changes in the local microflora and overgrowth of 1 or more bacterial types. This may be due in part to a reduction or loss in Lactobacillus that normally keeps the vagina slightly acidic, and/or a reduction or loss of peroxide-producing bacterial strains, which protect against BV.

Diagnosis relies on detection in wet mounts of the so-called "clue cells," which are vaginal epithelial cells infected by coccobacilli, that can be scored with a Gram stain.[24] Culture is neither helpful nor indicated for the diagnosis of BV. Of note, the presence of G vaginalis is not pathognomonic -- while it is present in approximately 92% of women with BV, it can be detected in up to 70% of asymptomatic women.

Molecular probes have now become available yielding results that compare well with high counts of G vaginalis. In this assay, 2 probes, a capture and a color-development probe, are used for the simultaneous detection of Candida, T vaginalis, and G vaginalis. A colorimetric assay has also been developed based on bacterial sialidases, a group of bacterial proteolytic enzymes that remove sialic acid residues from complex conjugates.[25]

Scored Gram stains, which represent the mainstay of BV diagnosis, can be interpreted as follows:

  • 0-3, normal

  • 4-6, intermediate (considered abnormal, it may indicate infection with trichomoniasis, Chlamydia trachomatis, or Neisseria gonorrhoeae, but it is not consistent with BV)

  • 7-10, consistent with presence of a BV.

Sensitivity of the scored Gram stain for G vaginalis was similar to that of the molecular probes (eg, 94% vs 95%); specificity was, however, still slightly higher with the Gram stain (82%) vs the probe (78%), thus yielding a higher positive predictive value (80% vs 75%). The advantages in using the molecular probes lie in the rapidity of execution, the good reproducibility, and the concomitant testing for 3 infectious agents. The latter may, however, represent a disadvantage when the other infections have already been ruled out or diagnosed. Additional disadvantages of the molecular probes include the high costs and the expertise needed to run them routinely.

In view of the complications that may accompany BV,[26,27] pregnant women with vaginal symptoms, or at high risk of preterm delivery, as well as women scheduled to receive gynecologic surgery, should be screened using one test or the other (also to rule out trichomoniasis). An appropriate diagnosis should also be sought for women with vaginal symptoms, particularly those who have failed prior therapy.

A timely diagnosis followed by appropriate treatment may well be more than cost-effective.[1,2] In a study by Oleen-Burkey and colleagues, complications associated with pregnancy cost $500 million to $1 billion every year. Screening and treatment of pregnant women with BV is estimated to cost only $5 million to $7 million annually.

Appropriate treatment of infected subjects and all sexual partners include[2,28,29,30]:

  • T vaginalis: metronidazole

  • Candida: miconazole, fluconazole, clotrimazole, or other antifungal agents

  • BV: clindamycin, metronidazole, and other agents

Prevention of all STDS, needless to say, is critically helped by education, counseling, and the use of condoms. And, as many well know -- these days, almost no one is too young to listen.

Streptococci B Vaginitis

Representing a category of its own, vaginal infections by group B Streptococci in pregnant women are not very frequent, but they need to be specifically addressed when they arise.[31] They are generally diagnosed at the end of pregnancy or at labor, by culture of vaginal or rectal specimens. Streptococci are identified by conventional microbiological techniques after isolation, or through specific molecular probes.

At variance from BV, vaginal infections by group B Streptococci are characterized by a desquamative inflammatory process, with macerations of vulvar and perianal tissues. In some women, however, infections may be asymptomatic[32,33]; hence, there is a new recommendation from the Centers for Disease Control and Prevention to routinely screen for this infection in pregnant women in the third trimester of pregnancy or at the time of delivery.


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