Mycoplasma pneumoniae is a bacterial infection that can affect anyone, but it is more common in school-aged children, teenagers and young adults. It is spread by droplets when infected people cough or sneeze, often in close-contact settings.
Mycoplasma pneumoniae infects the respiratory tract (throat, windpipe and lungs). Unlike typical pneumonia, which is sudden and severe, and affects older people or those who are already sick, mycoplasma pneumonia comes on gradually, has milder symptoms and affects otherwise healthy people. This is why it is often called walking pneumonia.
Sometimes a Mycoplasma pneumoniae infection can lead to severe pneumonia and need antibiotic treatment and admission to hospital. People who are at greater risk of more severe mycoplasma pneumonia symptoms are those who are recovering from another respiratory viral illness, already have lung disease or have a weakened immune system. Much less commonly, the infection can affect other organs such as the skin, heart, brain kidneys and/or liver.
It can take quite some time for symptoms to appear after exposure to the Mycoplasma bacteria. The average incubation period is 23 days and during this time, the bacteria are multiplying in your body, but you usually do not feel ill. This means you can be infected and unknowingly spread it before realising you are ill.
People with mycoplasma pneumonia are infectious for about 20 days. Immunity does not last long, so it is not uncommon for people to become infected again.
There is no vaccine for Mycoplasma pneumoniae.
Types of testing
Testing for Mycoplasma pneumoniae usually relies on:
When labs test for infectious disease, bacteria are sometimes stained and so they can be seen clearly and identified under a microscope. Mycoplasma pneumoniae bacteria are different from most other bacteria. They are extremely small and do not have a firm outer wall like other bacteria. Because of this, they are harder to see with standard lab tests that involve staining.
Also, bacteria are sometimes cultured in the lab to encourage any bacteria present to grow, so they can be identified and tested for antibiotic sensitivity. Mycoplasma pneumoniae bacteria are termed fastidious because they are fussy and hard to grow in the lab - they take a long time and require specially enriched media to grow in. For these reasons, most diagnostic laboratories do not attempt to grow the bacteria.
PCR (Polymerase Chain Reaction) tests - direct testing on a nose and throat swab or sputum.
PCR is a test that looks directly for the genetic material of the bacteria. In most cases, PCR is the preferred test because it is very accurate and it can detect infection early, even before symptoms are noticeable. It is especially useful in hospitals or during outbreaks.
Serology tests - indirect testing on a blood sample
These are tests that look for the antibodies your immune system makes to fight the bacteria. Serology can be used as an alternative to or as an addition to PCR. However, it takes time after you are infected before antibodies develop and you show a positive result. Two types of antibodies are tested. These are IgM and IgG.
IgM antibodies appear within 1 week of infection and peak at 3-6 weeks. IgG appears within 3 weeks. IgM may persist for many months after infection and IgG may remain high for more than a year after infection.
Serology limitations: Antibody testing is not reliable very early in the infection. Also, as most infections in adults are repeat infections interpreting serology results is difficult. Other infections may also cause false positive Mycoplasma antibody results.
Sample
Nose and throat swab or sputum.
Any preparation?
None.
Mycoplasma pneumoniae is not usually diagnosed on testing alone. Your health team will consider your results together with your symptoms and how likely it is that you have been exposed.
| Mycoplasma pneumoniae test result | What this may mean |
| PCR positive + typical symptoms | You most likely have an active Mycoplasma pneumoniae infection. |
| PCR positive + no symptoms | You have the bacteria present in your respiratory tract, but it is not causing illness, or else you have not long been infected and are still in the incubation period. |
| PCR negative + typical symptoms | A negative PCR result does not rule out the infection. It may be that your sample did not contain enough bacteria to be detected. A diagnosis may be made based on clinical suspicion, and not PCR alone. Sometimes a follow-up test (serology) will be ordered. |
| Rising antibodies (serology) | Two blood samples are taken weeks apart to see how the body’s antibody response changes. If antibody levels rise it indicates a recent infection. |
| Your PCR report may give the Ct (cycle threshold) value. A lower Ct means there was higher amount of the bacteria detected. A higher Ct means that a lower amount of bacteria was detected. | |
Other tests
Mycoplasma pneumoniae testing is often done as part of a respiratory multiplex panel. This tests for multiple pathogens at the same time.
| Example of a typical multiplex report | |
| Organism tested | Result |
| Influenza A | Not detected |
| Influenza B | Not detected |
| RSV | Not detected |
| SARS-CoV-2 | Not detected |
| Mycoplasma pneumoniae | Detected |
| Bordetella pertussis | Not detected |
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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