Sexually Transmitted Diseases... Health Article

Definition

Sexually transmitted diseases are infections spread from person to person through sexual contact. A culture is a test in which a laboratory attempts to grow and identify the microorganism causing an infection. Laboratory culture is performed to isolate and identify the causes of several sexually transmitted infections.

Purpose

Sexually transmitted diseases (STDs) produce symptoms such as genital discharge, pain during urination, bleeding, pelvic pain, skin ulcers, or urethritis. Often, however, they produce no immediate symptoms. Therefore, the decision to test for these diseases must be based not only on the presence of symptoms, but on whether or not a person is at risk of having one or more of the diseases. Activities such as drug use and sex with more than one partner put a person at high risk for these diseases. STD cultures are necessary to diagnose certain types of STDs. Only after the infection is diagnosed can it be treated and further spread of the infection prevented. Left untreated, consequences of these diseases range from discomfort to infertility to death. In addition, these diseases in a pregnant woman can be passed from mother to fetus.

Precautions

Some infections, particularly gonorrhea, can be difficult to culture. It may be necessary to culture other sites which may be infected, such as the anus and mouth if the patient has corresponding sexual habits which may put them at risk. Also, health care workers should be aware that testing of anyone who mentions a sexual assault must be done very carefully, following a protocol which is usually best carried out in the emergency room. The physician, nurse, or physician assistant performing sample collection should observe universal precautions for the prevention of transmission of bloodborne pathogens.

Description

Gonorrhea, bacterial vaginosis, candidiasis, chancroid, chlamydiosis, herpes, and mycoplasma are common sexually transmitted diseases that can be cultured. The organisms which cause the first three conditions are cultured routinely while those that cause the last four are more difficult to grow and are more frequently identified immunologically or by DNA amplification. Syphilis, human immunodeficiency virus, and trichomoniasis are sexually transmitted diseases that usually are not cultured because they do not grow on artificial culture medium.

The female patient will be in the dorsal lithotomy position (lying on the back with legs raised and bent) typical for Pap testing. A speculum is moistened with warm water (no lubricant should be used) and inserted into the vagina to secure good visualization of the cervix. Any excess cervical mucous should be removed with a cotton ball (held by ring forceps). A sterile swab is inserted just inside the opening of the cervix (the os) and rotated gently for 30 seconds. Genital swabs are usually placed in a transport medium that contains charcoal to absorb toxins that inhibit the growth of gonococcus.

Care should be taken not to touch the vaginal surfaces with the swab in order to avoid the transfer of normal vaginal flora. For culture, the sample is placed in Stuart or Amies transport medium with charcoal added and delivered to the laboratory at room temperature. Since Neisseria gonorrhoeae are very sensitive to drying and temperature changes, plating is performed as soon as possible. For DNA probe or immunological testing (in which organisms are not cultured), the swab is broken off at the top of the sterile tube provided, and the tube is capped and sent to the laboratory. For immediate viewing, a swab sample may be placed in normal saline. One drop can then be placed between a slide and coverslip, and viewed beneath the microscope. This is called a "wet prep." A wet prep is useful for diagnosing yeast infection and trichomoniasis. Pelvic inflammatory disease samples and samples from genital lesions such as chancres are collected by aspiration. Plating for H. ducreyi should be done from the chancre aspirate and performed immediately because the organism is fastidious.

In the male patient, a smaller sterile swab is used to remove cells and any discharge from the last 0.75 in (2 cm) of the urethra, and the swab is transported for culture (or DNA probe or immunological testing) as described for the female patient. If visible discharge is present on the surface of the penis, this should be swabbed, and it is unnecessary to enter the urethra. For anal specimens the physician inserts a sterile, cotton-tipped swab about 1 in(2.5 cm) into the anus and rotates the swab for 30 seconds. Stool must not contaminate the swab. For oropharynx (throat) specimens the person's tongue is held down with a tongue depressor, as a healthcare worker moves a sterile, cotton-tipped swab across the back of the throat and tonsilar region.