The Test Sample
What is being tested?
Mycoplasmas are the smallest free-living microorganisms known. They may exist as part of the normal flora found in the throat, upper respiratory tract, and genitourinary tract. Mycoplasmas are unlike other types of bacteria in many ways and can be difficult to culture and identify. Mycoplasma testing is used to determine whether someone currently has or recently had a mycoplasma infection.
Mycoplasma testing includes a group of tests that either measure antibodies in the blood produced in response to a mycoplasma infection or detect the microorganism directly through culturing or by detecting its genetic material (DNA) in a body sample. It is most often used to detect Mycoplasma pneumoniae (M. pneumoniae), the causative agent of respiratory infections often referred to as "atypical pneumonia."
M. pneumoniae is a common cause of upper respiratory infections, with an estimated 2 million cases in the U.S. each year. It is responsible for 15-20% of cases of community-acquired pneumonia, appearing as single cases and as periodic epidemics, especially in school-age children and in military populations or other settings where people live in close quarters. Infections can occur at any time of the year, but outbreaks are more prevalent in the late summer and early fall.
Most cases of M. pneumoniae infection are mild and self-limited, causing nonspecific symptoms such as bronchitis, a runny nose, and a nonproductive cough that may persist for several weeks. Symptoms may become more severe, causing fever, sore throat, headaches, and muscle aches, when the infection spreads to the lower respiratory tract and causes "walking pneumonia," or, more rarely, spreads to other parts of the body. This is especially true in very young infants, in those who have underlying health conditions, such as asthma, or who have compromised immune systems, such as those with HIV/AIDS. Depending upon what parts of the body become infected, complications may range from meningitis to difficulty breathing, cardiac inflammation and arrhythmia, skin rashes, lesions or nodules, arthritis, anemia, or to Guillain-Barré syndrome.
Testing may occasionally be done to detect other species of mycoplasma. Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma urealyticum infections are less common than those seen with M. pneumoniae. In adults, these organisms are primarily sexually transmitted, causing nongonococcal urethritis (NGU) and some inflammation of the prostate (prostatitis) in men and sometimes associated with vaginal discharge and pelvic inflammatory disease (PID) in women. M. hominis and U. urealyticum can be passed from mother to baby during birth when the baby passes through an infected birth canal. They typically colonize infants for their first couple of years. Rarely, they can cause systemic infections in infants and in those with compromised immune systems.
How is the sample collected for testing?
The sample required depends on the method being used and on the health status of the person being tested:
- Antibody testing requires a blood sample, obtained by inserting a needle into a vein in the arm.
- Direct detection of mycoplasma may be done on a variety of samples. For a respiratory infection, samples may include sputum, a washing of the bronchi in the lungs, or throat swab. If a systemic infection is being diagnosed, blood, joint fluid, body fluids, or tissues samples may be cultured. Some samples may require a special procedure to collect them. To detect a genital infection, a swab of the cervix or urethra may be collected.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.