Introduction

  • Mycoplasma pneumoniae is a small bacterium (one of the the smallest free-living organisms), that lacks a cell wall, which can cause a pneumonia in humans – termed mycoplasma pneumonia
  • Along with some other organisms (e.g. chlamydia pneumoniae) we often term these pneumonias atypical pneumonia as they do not respond to first line antibiotics (penicillins), and also frequently cause less severe symptoms
    • Because they lack a cell wall, beta-lactam antibiotics are useless against them – because beta-lactams inhibit cell wall synthesis!
  • Mycoplasma pneumoniae is thought to be responsible for about 5-15% of pneumonia in adults (up to 50% in localised outbreaks), and even higher rates in children
  • Most patients suffer a mild self-limiting illness and do not require antibiotics
  • It can be difficult to differentiate from an upper respiratory tract viral infection

 

Pathology

  • Incubation period 2-3 weeks
  • Infectious period – approx 20 days or less
  • Spread via respiratory droplets

Presenting features

  • Upper respiratory tract symptoms – runny nose, sore throat, ear pain
  • Fevers / sweats / chills
  • Dry cough
  • Headache
  • Sore throat
  • Chest soreness
  • General malaise
  • Pneumonia occurs in about 3-10% of cases
  • General malaise and fatigue can be present for 2 weeks or so after the resolution of the other symptoms – meaning the total duration of the illness can be about one month

Complications

These are rare, and may occur without concurrent respiratory tract symptoms

  • Encpehalitis
  • Carditis
  • Haemolytic anaemia

Diagnosis

  • Usually clinical
  • CXR is indicated if severe pneumonia is suspected – although atypical pneumonia does not commonly cause focal consolidation on CXR. Findings of atypical pneumonia on CXR include:
    • “Patchy opacities” – unilateral or bilateral
    • Interstitial infiltrates – often in streaks
    • Atelectasis
    • Small pleural effusions – unilateral or bilateral – in about 20% of cases
  • Bloods – likely to show raised inflammatory markers in more severe cases
  • Mycoplasma PCR is available in some centres – usually from a nasopharyngeal swab
    • In outbreaks, testing ay be conducted as a public health measure to assess the spread of disease
    • Be aware that many people carry mycoplasma pneumoniae asymptomatically – so a positive swab doesn’t necessary mean active disease.
  • MC+S – mycoplasma does not usually culture well and results are often negative. Because it lacks a cell wall it does not Gram stain. Most laboratories don’t try to culture for mycoplasma.
  • Serology – it is possible to test for IgG, but not regularly performed.

Treatment

  • Most cases are self-limiting and mild
  • Antibiotics can improve the speed of recovery if given early in the course of the illness – but are NOT thought to reduce the infective period
  • In the absence of features of pneumonia, supportive treatment is all that is required
  • Antibiotics reserved for those with severe pneumonia
  • Macrolides are the treatment of choice
    • Doxycycline
    • Azithromycin
    • Macrolide resistance is growing in Asia and some parts of Europe – in parts of China and Japan, resistance is as high as 95%
  • Fluoroquinolones are an alternative
    • Ciprofloxacin
    • Levofloxacin
    • Moxifloxacin
  • Check local guidelines for exact drugs and doses

 

Prevention

  • No vaccine is available
  • School / work or childcare exclusion is not necessary
  • Basic respiratory infectious disease advice
    • Frequent hand washing
    • Cough coughs and sneezes with the inside of the elbow – NOT the hands
  • Post-Exposure prophylaxis is warranted for immunocompromised individuals only