Other venereal diseases include lymphogranuloma venereum (caused by a subspecies of C. trachomatis different from the one that causes nongonococcal urethritis), syphilis, granuloma inguinale, trichomoniasis, chancroid, herpesvirus type 2, molluscum contagiosum, and condyloma acuminatum. Most of these will be discussed elsewhere.

Gardnerella vaginalis

This organism (also called Corynebacterium vaginalis and Haemophilus vaginalis) is a small bacillus or coccobacillus that gives variable results on Gram stain, most often gram negative, but sometimes gram positive. The organism has been implicated as the cause of most cases of “nonspecific vaginitis” (i.e., vaginitis not due to Candida albicans or Trichomonas). Clinical infection in women occurs only when estrogen levels are normal or increased, so postmenopausal women usually are not involved. Gardnerella vaginalis can also be cultured from the urethra of many male sexual partners of infected women, so the disease is postulated to be at least potentially sexually transmissible.

Clinically, there is a vaginal discharge that typically is malodorous (although this odor was present in only two thirds of cases in one report). Other than the discharge, there usually are few or no symptoms in the female and none in the male.

Diagnosis is usually made either from aspiration of vaginal discharge or from swab specimens of the vaginal wall (avoiding the cervix). The vaginal discharge specimens have a pH greater than 4.5, with 90% between 5.0 and 5.5 (normal pH is <4.5 except during menstruation, when the presence of blood raises the pH to 5.0 or more). Trichomonas parasitic infection may also produce a vaginal discharge with a pH greater than 4.5, whereas the pH in Candida infection usually is less than 4.5. Therefore, a discharge with a pH less than 4.5 is strong evidence against Trichomonas or Gardnerella infection, whereas a discharge with a pH greater than 5.0 suggests infection by these organisms. Addition of 10% sodium hydroxide to the specimen from G. vaginalis infection typically results in a fishy odor. A wet mount or Gram stain of discharge or swab material from the vaginal wall (avoiding the cervix) demonstrates clue cells in about 90% of G. vaginalis infections (literature ranges in the few studies available are 76%-98% for wet mount and 82%-100% for Gram stain). Clue cells are squamous epithelial cells with a granular appearance caused by adherence of many tiny G. vaginalis gramegative bacteria. Wet mount may sometimes be difficult to interpret due to degeneration of the squamous epithelial cells or because of only partial coverage of the cell by the Gardnerella organisms. Wet mount may occasionally produce a false positive result, and Gram stain is usually easier to interpret and generally more accurate; but one investigator found it to be somewhat more liable to false positive errors by mistaking diphtheroids for G. vaginalis. Papanicolaou cytology stain can also be used. The organism can be cultured on special media or on the same Thayer-Martin medium with increased carbon dioxide that is used for the diagnosis of gonorrhea. However, isolation of Gardnerella is not diagnostic of vaginitis, since Gardnerella can be cultured from the vagina in 42%-50% of clinically normal women. In addition, there is substantial evidence that anaerobic bacteria are associated with symptomatic infection by G. vaginalis.

Several studies suggest that Gardnerella is responsible for urinary tract infection in some pregnant patients and some patients with chronic renal disease. Since Gardnerella does not grow on culture media routinely used for urine, urine culture in these patients would be negative. However, Gardnerella has been isolated with equal frequency in similar patients without clinical evidence of urinary tract infection.