Sexually Transmitted Diseases... Health Article

Mycoplasma and Ureaplasma

Three types of mycoplasmal organisms cause sexually transmitted disease: Mycoplasma hominis, Mycoplasma gentialium, and Ureaplasma urealyticum. M. hominis causes pelvic inflammatory disease (PID) and pyelonephritis in females but does not cause urethritis, vaginitis, or cervicitis. Ureaplasma urealyticum can cause urethritis in males and may cause PID in females but does not cause vaginitis or cervicitis. M. gentialium has been implicated as a cause of urethritis and PID. Samples are collected from the cervix in a female, and from the urethra (or urine) in a male. Swabs must be immediately placed in sucrose-phosphate or other acceptable transport medium and transported to the lab immediately. These organisms will grow on New York City agar and M. hominis will also grow on CNA plates, but swabs should be inoculated onto a selective agar or broth such as SP-4 which differentiates Mycoplasma from Ureaplasma based upon the ability of the latter to hydrolyze urea. Cultures are incubated aerobically at 96.8°F (36°C) and grow for two to four days. Colonies are very small and difficult to see with the unaided eye. When growth is seen, a portion of the agar is removed and stained with Dienes stain. The colonies are examined under a microscope for their characteristic fried egg appearance. They will have a dark blue center and light blue periphery. These organisms cannot be seen with the Gram stain.

Chlamydiosis

Chlamydiosis is caused by the gram-negative bacterium Chlamydia trachomatis. It is one of the most common STDs in the United States (approximately three million cases occur each year), and generally appears in sexually active adolescents and young adults. While chlamydiosis often does not have any initial symptoms, it can if left untreated lead to pelvic inflammatory disease and sterility. Samples are collected from one or more of these infection sites: cervix in a female, urethra in a male, or the rectum. Swabs must be immediately placed in sucrose-phosphate or other acceptable transport medium and transported to the lab immediately. Culture is successful in recovering Chlamydia trachomatis about 80% of the time. The organism is inoculated onto monolayers of malignant tissue culture cells such as HeLa cells or McCoy cells in shell vials. The cultures are incubated for two to three days at 96.8°F (36°C) in 5–10% carbon dioxide. Following this they are stained with flourescentlabeded monoclonal antibodies to the major outer membrane protein (MOMP) to identify the characteristic chlamydial inclusions. This technique is expensive and requires a high level of tissue culture expertise. Consequently most labs use non-culture tests such as enzyme immunoassay or DNA amplication methods to diagnose chlamydial infections.

Genital herpes

Herpes is generally diagnosed based on the patient's symptoms and the physical exam. Approximately twothirds of genital herpes is caused by herpes simplex 2 (HSV-2) and the remainder by herpes simplex 1 (HSV-1). Extremely painful blisters around the genital area are classic for initial herpes presentation. However, if questions remain, the herpes virus can be cultured from a vesicle (blister) which has been "unroofed" carefully with a scalpel blade. The base of the vesicle is swabbed with a sterile cotton applicator, and the virus taken to the laboratory in a tube of viral transport medium. Herpes can be cultured in several cell lines including human diploid fibroblasts (HDF), HEp2 cells (epithelial cancer cells from the larynx), primary monkey kidney cells (PMK), and rabbit kidney cells (RK). Cell cultures are inoculated and allowed to grow for one to three days at98.6°F (36°C) in 5–10% carbon dioxide. Usually by the end of the first day of culture the cytopathic effect (CPE) can be seen by observing the cells under a microscope. Herpes induces the formation of giant cells.

Antibiotic susceptibility testing

Antibiotic susceptibility is not usually required for organisms isolated from a genital culture. Gonorrhea is treated with penicillin or related drugs. Chlamydiosis and mycoplasmal infections are treated with erythromycin. Herpes is treated with acyclovir or related antivirals. Candida is treated with clotrimazole or other antifungal. Bacterial vaginosis is treated with metronidazole, Haemophilus ducryi is treated with ceftriaxone or erythromycin.

Preparation

Cultures should always be collected before the person begins taking antibiotics. Men should not urinate within one hour before collection of a urethral specimen. Women should not douche or take a bath within 24 hours of collection of a cervical or vaginal culture.

Aftercare

Patients should be instructed to have no sexual contacts until test results are reported.

Complications

The minor discomforts of genital testing are short lived, and no significant complications are common.