Community-acquired and often seen in young adults living in close proximity.
Diagnosis is mostly clinical. Molecular-based diagnosis of throat swabs or sputum can be performed. Serology can be used to confirm the diagnosis.
Treatment is often outpatient based with a macrolide antibiotic or doxycycline.
Extrapulmonary manifestations may occur, especially in Mycoplasma pneumoniae infections.
Atypical bacterial pneumonia is caused by atypical organisms that are not detectable on Gram stain and cannot be cultured using standard methods. The most common organisms are Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. Atypical bacterial pneumonia generally is characterised by a symptom complex that includes headache, low-grade fever, cough, and malaise. Constitutional symptoms often predominate over respiratory findings. Although in most cases presentation can be in the milder spectrum of community-acquired pneumonia, some cases, especially if caused by L pneumophila, may present as severe pneumonia, necessitating intensive care unit admission. Other possible pathogens include Chlamydophila species, Legionella species, Coxiella burnetii (Q fever), and respiratory viruses.
History and exam
Key diagnostic factors
- presence of risk factors
- age <50 years
- persistent cough
- dry cough
- long duration of symptoms
Other diagnostic factors
- recent community exposure
- throat involvement
- bullous myringitis
- lung rales/crepitations
- close community settings
- cigarette smoking
- chronic lung disease
- male sex
- immunomodulating drugs
1st investigations to order
- chest x-ray
- WBC count
- oxygen saturation in air
- serum urea level
- real-time reverse transcription polymerase chain reaction (RT-PCR) for SARS-CoV-2
Investigations to consider
- urinary Legionella antigen
- sputum culture for Legionella
- molecular diagnosis of Mycoplasma pneumoniae or Chlamdophila pneumoniae
- serology for atypical pathogens
- nasopharyngeal viral cultures
presumed atypical bacterial pneumonia: non-pregnant adult
presumed atypical bacterial pneumonia: pregnant or child
Ran Nir-Paz, MD
Associate Professor in Medicine
Department of Clinical Microbiology and Infectious Diseases
Hadassah Hebrew University Medical Center
RNP declares that they have no competing interests.
Mark Woodhead, BSc, DM, FRCP
Honorary Senior Lecturer (University of Manchester)
Consultant in General & Respiratory Medicine
Department of Respiratory Medicine
Manchester Royal Infirmary
MW is an author of a reference cited in this topic.
Ethan Rubinstein, MD
H.E. Sellers Research Chair in Infectious Diseases
Section of Adult Infectious Diseases
Department of Internal Medicine
Department of Medical Microbiology
University of Manitoba
At the time of the peer review, Professor Rubinstein declared no competing interests. We were made aware that Professor Rubinstein is now deceased.
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