Community-acquired and often seen in young adults living in close proximity.
Atypical bacterial pneumonia is most commonly caused by Mycoplasma pneumoniae , Chlamydophila pneumoniae , or Legionella pneumophila .
Usually presents with a low-grade fever, persistent dry cough, and constitutional symptoms, for example, malaise.
Diagnosis is mostly clinical. Molecular-based diagnosis (e.g., PCR) of throat swabs or sputum can be performed. Serology can be used to confirm the diagnosis. For L pneumophila , special tests for serotype 1 (80% of cases) are available.
Treatment is often outpatient based with a macrolide or doxycycline.
Extrapulmonary manifestations may occur, especially in M 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 characterized 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 ICU admission. Other possible pathogens include Chlamydophila species, Legionella species, Coxiella burnetii (Q fever) and respiratory viruses.
Associate Professor in Medicine
Department of Clinical Microbiology and Infectious Diseases
Hadassah Hebrew University Medical Center
RNP is chairman of the International Research Program on Comparative Mycoplasmology group Clinical Aspects of Human Mycoplasmas, and chairman of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Mycoplasma Infections (ESGMI).
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 monograph.
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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