Many of the prescribed antipseudomonal drugs for patients with community-acquired pneumonia (CAP) are potentially unnecessary, according to the results of a prospective, observational study published in the Annals of the American Thoracic Society.

Pneumonia due to Pseudomonas aeruginosa is associated with high mortality and requires antipseudomonal treatment, but because P aeruginosa can colonize the respiratory tract, the diagnosis of pathogenic P aeruginosa involvement may be challenging. Therefore, researchers in Japan aimed to determine the prevalence of definitive and indeterminate P aeruginosa infection in CAP, to describe these clinical and microbiologic profiles, and to estimate the burden of unnecessary antipseudomonal drug prescriptions.

A total of 2701 patients with CAP were prospectively enrolled, using stringent criteria for diagnosing P aeruginosa pneumonia, generated 3 groups: 1) definitive P aeruginosa, 2) indeterminate P aeruginosa, and 3) non-P aeruginosa pneumonia. The median age of the patients was 76 years, 72% were older than 65 years, and approximately 40% were women.

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In this study population, the prevalence of definitive P aeruginosa pneumonia was 0.9% (n=25) and indeterminate P aeruginosa pneumonia was 4.9% (n=131). Considerable clinical differences were observed among the groups, with patients with definitive P aeruginosa pneumonia being more likely to have a history of tuberculosis (16%) and chronic obstructive pulmonary disease (COPD)/bronchiectasis (56%) and a higher 30-day mortality (28%) than patients with non-P aeruginosa pneumonia.

In addition, patients with indeterminate P aeruginosa pneumonia were more likely to have comorbidities than patients with non-P aeruginosa pneumonia. While more than half of patients with indeterminate P aeruginosa and 25% of patients with non-P aeruginosa pneumonia were treated with an antipseudomonal drug, no patients with definitive P aeruginosa pneumonia had multidrug resistance.

“In conclusion, the prevalence of definitive [P aeruginosa] pneumonia among CAP patients was low, and the clinical features and outcomes were considerably different among the [P aeruginosa] categories,” stated the authors. They added, “The establishment of stringent criteria for diagnosing CAP is needed to avoid prescribing unnecessary antipseudomonal drugs.”

Disclosure: This clinical trial was supported by Pfizer. Please see the original reference for a full list of authors’ disclosures.  


Sando E, Suzuki M, Ishida M, et al. Definitive and indeterminate Pseudomonas aeruginosa infection in adults with community-acquired pneumonia: a prospective observational study. Ann Am Thorac Soc. Published online February 10, 2021. doi:10.1513/AnnalsATS.201906-459OC