Epidemiology and Outcomes of Community-Acquired Escherichia coli Pneumonia

Background. E. coli is an under-recognized cause of bacterial community-acquired pneumonia (CAP). The objective of this study was to describe the epidemiology, risk factors, and outcomes of community-acquired Escherichia coli pneumonia in comparison with other gram-negative and pneumococcal pneumonias. Methods. We conducted a large retrospective cohort study of adult patients admitted with pneumonia to 173 US hospitals included in the Premier Research database from July 2010 to June 2015. Patients were included if they had a principal diagnosis code for pneumonia or a principal diagnosis of respiratory failure or sepsis with a secondary diagnosis of pneumonia and had a positive blood or respiratory culture obtained on hospital day 1. The primary outcome was in-hospital case fatality. Secondary outcomes included intensive care unit admission, invasive mechanical ventilation, and use of vasopressors. Results. Of 8680 patients with pneumonia and positive blood or respiratory cultures, 1029 (7.7%) had E. coli CAP. Patients with E. coli pneumonia were older and more likely to have a principal diagnosis of sepsis. Patients with E. coli pneumonia had significantly higher case fatality than patients with pneumococcal pneumonia (adjusted odds ratio, 1.55; 95% CI, 1.23-1.97), but it was not significantly different than other gram-negative pneumonias (adjusted odds ratio, 1.06; 95% CI, 0.85-1.32). Approximately 36% of the isolates were resistant to fluoroquinolones; 9.3% were resistant to ceftriaxone. Conclusions. E. coli is an important cause of severe CAP; with mortality that was higher than pneumococcal pneumonia but similar to other gram-negative pneumonias. The rate of fluoroquinolone resistance was high, and empiric fluoroquinolones should be used with caution in these patients.