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