By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: The 2019 guideline differs from the 2007 version to only a limited extent.

SOURCE: Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Resp Crit Care Med 2019;200:e45-e67.

The following is a brief summary of recommendations in the new community-acquired pneumonia (CAP) guideline.

Sputum Gram Stain and Culture, Blood Culture.

It is recommended that these should not be routinely performed in individuals with CAP managed as outpatients. In contrast, it is recommended that these tests be performed in those with severe infection or for whom empiric treatment for methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa infection is administered, those with previous infection with one of these organisms, or those who have received parenteral antibiotics while inpatients in the previous 90 days.

Urine Pneumococcal Antigen.

Not routinely recommended, except in severe CAP.

Urine Legionella Antigen.

Not routinely recommended except in those with severe CAP and/or associated epidemiological factors (e.g., in an outbreak or after travel). Culture on selective media or Legionella nucleic acid amplification testing is also recommended for those with severe infection.

Influenza Virus Testing.

Rapid influenza nucleic acid amplification testing is recommended when influenza viruses are circulating in the community.

Serum Procalcitonin Implication for Initiation of Empiric Antibiotic.

Serum procalcitonin results should not affect the decision to initiate empiric antibiotic therapy, which should be administered to all adults suspected to have CAP on clinical grounds and for whom it is radiographically confirmed.

Choosing Outpatient vs. Inpatient Management.

Clinical judgment together with the Pneumonia Severity Index (PSI) or the CURB-65 tool should be used to determine the need for hospitalization. PSI is preferred over CURB-65.

Determining the Level of Inpatient Care.

Direct admission to the intensive care unit is indicated for vasopressor-requiring hypotensive patients and/or those requiring mechanical ventilation because of respiratory failure. In others, clinical judgment together with use of the 2007 IDSA/ATS severity criteria, can be used.

Empiric Antibiotic Therapy Outpatient Management.

In the absence of comorbidities, amoxicillin, doxycycline, or a macrolide may be used, although macrolide monotherapy should be used only in areas where the proportion of pneumococci resistant to this class of agents is < 25%. In patients with significant comorbidities, the recommended choices are amoxicillin/clavulanate or a cephalosporin (cefpodoxime or cefuroxime), each together with a macrolide or doxycycline. Monotherapy with a respiratory fluoroquinolone is an alternative to combination therapy.

Inpatient Empiric Antibiotic Therapy Absent Risk Factors for MRSA or P. aeruginosa Infection.

The preferred regimen for those with non-severe CAP is either ampicillin/sulbactam, cefotaxime, ceftriaxone, or ceftaroline each together with a macrolide. Alternatively, monotherapy with levofloxacin or moxifloxacin may be used. Finally, the recommendation for patients with contraindication to both fluoroquinolone and macrolide therapy is one of the beta-lactams listed above together with doxycycline.

For patients with severe infection, one of the above beta-lactams together with a macrolide or a respiratory fluoroquinolone may be used.

Inpatient Empiric Antibiotic Therapy With Suspected Aspiration Pneumonia Anaerobic Coverage.

The recommendation is to not routinely add anaerobic coverage in patients with suspected aspiration pneumonia in the absence of a known or suspected empyema or lung abscess.

Inpatient Empiric Antibiotic Therapy With Risk Factors for MRSA or P. aeruginosa Infection.

Empiric coverage for MRSA or P. aeruginosa infection is recommended only if locally validated (local prevalence in CAP and local risk factors) are present.

Therapy in the Inpatient Setting Adjunctive Corticosteroids.

The guideline recommends that neither patients with severe nor nonsevere CAP routinely receive corticosteroids, including those with severe influenza pneumonia. However, the guideline does endorse the recommendation of the Surviving Sepsis Campaign for corticosteroid use in refractory septic shock, defined as unresponsive to fluids and vasopressors.

CAP and Influenza Virus Infection.

Administration of antiviral therapy is recommended for adults with CAP in both the inpatient and outpatient settings regardless of the duration of illness. Patients in either setting with CAP and influenza virus infection should also initially receive standard empiric antibiotic therapy for CAP.

Duration of Antibiotic Therapy in Adult Outpatients and Inpatients With CAP.

Antibiotic therapy duration is determined by the achievement of clinical stability, as guided by a validated set of criteria and for at least five days.

Follow-Up Chest Imaging.

Follow-up chest imaging is not routinely recommended in patients whose symptoms resolved by five to seven days.


There are not many significant differences in the 2019 guideline compared to those from the 2007 version. Recommended sputum and blood culture use has been expanded to include not only patients with severe infection, as previously recommended, but also inpatients given empiric treatment for MRSA and/or P. aeruginosa infection. Macrolide monotherapy in outpatients without comorbidities should be used only if the local prevalence of resistance is < 25%, a distinction not made in 2007. The category of “healthcare-associated pneumonia” (HCAP) has been eliminated in favor of using local epidemiology and validated risk factors for MRSA or P. aeruginosa infection, together with increased emphasis on subsequent de-escalation. For standard empiric therapy of patients with severe CAP, a preference is now expressed for the combination of a macrolide, over a fluoroquinolone, with a beta-lactam. The use of procalcitonin testing to determine the need for antibiotic therapy, adjunctive corticosteroid administration, and/or routine follow-up chest imaging, none of which were discussed in 2007, is not recommended.

One can quibble over a number of the guideline recommendations, but they provide a valuable touchstone for clinical management of patients with CAP, despite the fact that so many of the recommendations are based on low or very low quality of evidence. Also, the guidelines do not take a stand on two antibiotics, omadacycline and lefamulin, recently approved for the treatment of CAP.

Overall, however, it is clear how little we have advanced in our knowledge of the management of adults with CAP in the 12 years since the last version of this guideline.