Difference of Clinical Manifestation Between Infection and Colonization of Pseudomonas aeruginosa Among Patients With Community-Acquired Pneumonia

Background: Distinguishing Pseudomonas aeruginosa infection and colonization from respiratory samples is challenging. We aimed to determine useful markers for differentiating P. aeruginosa infection from colonization in community-acquired pneumonia (CAP) patients.

Methods: We included CAP patients in whom P. aeruginosa was isolated from sputum but were not initially treated with P. aeruginosa-targeting antibiotics. Patients cured with antibiotics not targeting P. aeruginosa were defined as colonization cases, and those unresponsive to antibiotics not targeting P. aeruginosa and cured with antibiotics targeting P. aeruginosa were defined as infection cases.

Results: Of 299 CAP patients, 203 (68%) were treated with antibiotics not targeting P. aeruginosa in their initial regimen. After excluding 73 of 203 patients who were not cured with antibiotics targeting P. aeruginosa in subsequent regimens, 17 and 113 were classified as infection and colonization cases, respectively. Systolic blood pressure in the infection group was significantly lower than that in the colonization group (odds ratio = 0.971, 95% confidence interval: 0.946-0.996); no other significant differences were observed.

Conclusions: Low systolic blood pressure might be a useful marker for distinguishing isolated P. aeruginosa that need to be targeted from those that do not need to be targeted. However, interventional research is required to validate our study results.