Last reviewed: 30 Sep 2020
Last updated: 19 Nov 2019
19 Nov 2019

US guidelines on community-acquired pneumonia updated

The American Thoracic Society and the Infectious Diseases Society of America have updated their guidelines on diagnosing and treating community-acquired pneumonia (CAP) in adults. The guideline makes recommendations in response to key decisions facing clinicians caring for patients with CAP, including diagnostic testing, site of care, selection of initial empiric antibiotic therapy, and subsequent disease management. The updated guideline reaffirms many recommendations from the 2007 version; however, new evidence and a new process have led to significant changes, namely:

  • Sputum and blood cultures are now recommended in all inpatients treated empirically for methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa, as well as patients with severe disease, to avoid unnecessarily prescribing antibiotics for drug-resistant bacteria.

  • The recommendation for macrolide monotherapy in outpatients has been downgraded from a strong recommendation to a conditional one based on resistance levels.

  • The recommendation for combination therapy with a beta-lactam plus a macrolide, or a beta-lactam plus a fluoroquinolone in severe infection remains; however, the evidence is stronger for the beta-lactam/macrolide combination.

  • The guidelines generally recommend against the use of corticosteroids, although acknowledge that they may be considered in patients with refractory septic shock.

  • The guidelines also recommend against routine follow-up chest imaging in patients who are improving, and the use of procalcitonin to guide initial antibacterial therapy.

"The new guideline highlights the substantial increase in the proportion of patients requiring routine respiratory tract samples for microbiological investigation in order to avoid the unnecessary use of broad-spectrum antibiotic therapy", say Catia Cilloniz and Antoni Torres, authors of this topic. "Another important point to highlight is that new studies are required in order to investigate the role of corticosteroids in patients with refractory septic shock, focusing on patients who may benefit or be potentially harmed from its use."

CAP remains one of the leading causes of deaths in the world.

See Diagnosis: approach

See Management: approach

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History and exam

Key diagnostic factors

  • cough with increasing sputum production
  • fever or chills
  • dyspnea
  • pleuritic pain
  • abnormal auscultatory findings

Other diagnostic factors

  • dullness to percussion
  • myalgia
  • arthralgia
  • confusion

Risk factors

  • age >65 years
  • residence in a healthcare setting
  • COPD
  • exposure to cigarette smoke
  • alcohol abuse
  • poor oral hygiene
  • use of acid-reducing drugs, inhaled corticosteroids, antipsychotics, antidiabetic drugs
  • contact with children
  • HIV infection
  • diabetes mellitus
  • chronic renal disease
  • chronic liver disease
  • use of opioids

Diagnostic investigations

1st investigations to order

  • chest x-ray
  • CBC
  • serum electrolytes/blood urea nitrogen
  • liver function tests
  • blood glucose
  • arterial blood gases/oximetry
  • blood culture
  • sputum culture
More 1st investigations to order

Investigations to consider

  • lung ultrasound
  • CT chest
  • urinary antigen testing for Legionella and pneumococcus
  • serum C-reactive protein
  • serum procalcitonin
  • thoracocentesis and pleural fluid culture
  • bronchoscopy
  • tests for respiratory viruses
  • molecular microbiological techniques
More investigations to consider

Treatment algorithm


Post-doctoral Research

Pneumology Department

Hospital Clinic of Barcelona






CC is an author of a number of references cited in this topic.

Professor of Medicine


Pulmonary Intensive Care Unit

Respiratory Institute

Hospital Clinic of Barcelona




AT is an author of a number of references cited in this topic.

Dr Catia Cilloniz and Professor Antoni Torres would like to gratefully acknowledge Dr M. Nawal Lutfiyya, Dr Linda Chang, and Dr Robert Bales, previous contributors to this topic.


MNL is an author of a reference cited in this topic. LC and RB declare that they have no competing interests.

Peer reviewersVIEW ALL

Assistant Professor

Division of Pulmonary and Critical Care Medicine

University of Utah

Salt Lake City



BJ declares that she has no competing interests.

Associate Professor

Departments of Emergency Medicine and Medicine

Icahn School of Medicine at Mount Sinai

New York



DN declares that she has no competing interests.

Professor of Medicine

Royal Perth Hospital




GW declares that he has no competing interests.

Professor of Respiratory Infection/Honorary Consultant

University College London




JB was a member of the NICE pneumonia guidelines committee.

Professor (clinical) of Medicine

Section Chief Pulmonary Critical Care Medicine

University of Utah

Intermountain Medical Center




ND declares that he has no competing interests.

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