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Community-Acquired Pneumonia: An Opportunity for Antimicrobial Stewardship

Amesh A. Adalja, MD, FACP, FACEP, FIDSA, January 22, 2016

With the continued (and well-deserved) attention being directed to appropriate antimicrobial prescribing, as well as the crucial role of epidemiologic tracking of infectious disease, the ability to make a specific microbe-level diagnosis has become increasingly important. The standard of care in most hospitals for community-acquired pneumonia—a common reason for antimicrobial use—is to use guideline-concordant therapies based on the most likely etiology. However, by definition, guidelines are one size fits all and should be tailored to specifically fit the individual patient and to direct therapy narrowly at the pathogen causing the pneumonic process. A recent study from the Royal Infirmary of Edinburgh, published in Clinical Infectious Diseases, provides important insight into the pathogen ecology of community-acquired pneumonia.1


Standard Culture Diagnosis 40%

The study involved 323 adult patients with pneumonia who were admitted to 2 tertiary care centers. Respiratory tract samples were tested using standard culture, and molecular diagnostic testing was done for 26 bacterial and viral pathogens. Using standard culture, 39.3% of patients were able to receive a pathogen-specific diagnosis. By contrast, molecular diagnostic testing revealed a pathogen (viral or bacterial) in 86.7% of patients.1

Hemophilus influenza and Streptococcus pneumoniae (pneumococcus) were the most commonly detected bacteria found in 40% and 36% of patients, respectively. Of those with viral infections, the majority were involved in co-infections with bacterial agents (81.6%). Rhinovirus and influenza were the most common isolates.1

Clinical results had the potential to lead to antimicrobial de-escalation in 77% of patients.1


A New Standard of Care

This paper is remarkable for many reasons, one of which is the fact that a pathogen-specific diagnosis was made in such a high number of patients despite the fact that blood culture and urinary antigen data were not used (vs. 38% in a similar study by the CDC EPIC team2). These studies illustrate the pressing need to incorporate more extensive diagnostic testing in the care of pneumonia patients, who are too often treated with broad-spectrum therapies for too long. Such management can be more costly, lead to adverse drug events, and can damage the patient’s microbiome. De-escalation of antimicrobial therapy is the cornerstone of using antimicrobials judiciously, and while not all hospitals have access to sophisticated molecular diagnostics, many do not use the tools they have (eg, urinary antigen tests, sputum culture, influenza testing, RSV testing, procalcitonin). Using all the noninvasive diagnostic tools at our disposal should become the new standard of care.



  1. Gadsby NJ, Russell CD, McHugh MP, et al. Comprehensive molecular testing for respiratory pathogens in community-acquired pneumonia. Clin Infect Dis 2016. Accessed January 20, 2016.
  2. Jain S, Self WH, Wunderink RG, et al. Community-acquired pneumonia requiring hospitalization among U.S. adults. N Engl J Med 2015;373:415-427.