Mycoplasma pneumoniae

What is Mycoplasma pneumoniae?

Mycoplasma pneumoniae is a bacterium which can cause acute respiratory infections. Infections are usually mild with upper respiratory tract infection and acute bronchitis common, but it can cause pneumonia in approximately 5-10% of cases. Infections can occur throughout the year but tend to occur most frequently in the late summer and autumn. Mycoplasma pneumoniae infections are not notifiable in Ireland however outbreaks of this infection are notifiable as clusters of disease.

How is it spread?

M. pneumoniae bacteria spread by person-to-person contact. When someone infected with M. pneumoniae coughs or sneezes, they create small respiratory droplets that contain the bacteria. Other people can get infected if they breathe in those droplets.

The disease may spread between people who live together. Outbreaks can also occur in crowded settings such as schools, college residences, nursing homes and hospitals. Most people who spend a short amount of time with someone who is sick with M. pneumoniae do not get infected.

How long after infection do symptoms appear?

Once someone becomes infected with the bacteria, symptoms usually appear 1 to 3 weeks later. Some infections may be asymptomatic.

What are the symptoms?

Infections can occur in the upper or lower respiratory tract, and symptoms may vary depending on the type of infection.  

In general infections are mild but may become more severe in some people. Illness onset may be gradual, progressing slowly and with a persistent cough that may last several weeks. Symptoms may include:

  • Sore throat
  • Fever
  • Cough
  • Headache
  • Fatigue

More severe infection may result in shortness of breath. Some infections may also have symptoms that affect areas other than the respiratory tract (extrapulmonary manifestations, see complications).

Children younger than five years of age may have different symptoms such as coryza (symptoms of a head cold e.g. sneezing, runny nose) and wheezing. Progression to pneumonia is relatively uncommon.

Who is at risk?

People of all ages can get M. pneumoniae, but it usually affects people aged younger than 40, most often those aged 5 to 20 years old. People living or working in crowded settings are also at increased risk. People at increased risk for serious infection include those who are immunocompromised.

What are the complications?

Most cases are mild, but complications may occur that require care in hospital. These may occur with or without respiratory symptoms and include:

  • Serious pneumonia
  • Asthma attacks
  • Pleural effusion
  • Haemolysis
  • Skin disorders such as erythema multiforme and Stevens-Johnson syndrome
  • Gastrointestinal complaints may include vomiting, diarrhoea and abdominal pain
  • Central Nervous System involvement such as encephalitis (swelling of the brain)
  • Arthralgia (joint pains)
  • Cardiovascular involvement such as myocarditis (inflammation of the heart muscle)
  • Renal dysfunction such as glomerulonephritis (kidney problems)

What is the treatment?

Most infections are mild and self-limiting and will recover without antibiotics. Pneumonia caused by M. pneumoniae is usually treated with antibiotics. Antibiotics can help patients recover from the infection faster if started early on.

There are several antibiotics available to treat pneumonia caused by M. pneumoniae including:

  • Macrolides (e.g., azithromycin, clarithromycin or erythromycin)
  • Tetracyclines (e.g., doxycycline)
  • Fluoroquinolones (e.g., levofloxacin)

Antibiotic choice may depend on the age of the patient and local antibiotic resistance patterns. M. pneumoniae is resistant to beta-lactam antibiotics (e.g., penicillin).

How can it be prevented?

There is no vaccine to prevent Mycoplasma pneumoniae infections. However like most respiratory illnesses, good respiratory virus etiquette can prevent further spread. Some tips include:

  • Cover your mouth or nose with a tissue when coughing or sneezing
  • Dispose of used tissues in waste
  • Good hand washing
  • Stay at home if you are ill.

Date Published: 28/11/2023