β-Lactams plus doxycycline versus azithromycin for treatment of severe community-acquired pneumonia in critically ill patients

Abstract Objectives Community-acquired pneumonia (CAP) is a significant source of hospital admissions and mortality. Atypical organisms are implicated in up to 40% of cases of CAP diagnoses. We studied the difference in outcomes of severe CAP patients treated with doxycycline versus azithromycin in addition to β-lactam therapy. Patients and methods This was a prospective observational cohort study from March 2020 to July 2022 in a medical ICU (MICU) of an academic quaternary medical center. Adults ≥18 years admitted to the MICU receiving doxycycline or azithromycin in addition to β-lactam therapy for the treatment of CAP were included for analysis. The primary outcomes were in-hospital and 30 day mortality. Secondary outcomes were ICU and hospital length-of-stay, 30 day readmission, days of mechanical ventilation, escalation and duration of antibiotics, adverse effects such as Clostridioides difficile infection and QTc prolongation. Results Sixty-three patients were in the azithromycin group and eighty-six patients in the doxycycline group. Both groups had similar APACHE IV and CURB-65 scores. The mean Charlson Comorbidity Index score was higher for the doxycycline group compared with the azithromycin group (P = 0.04). There was no statistically significant difference in in-hospital and 30 day mortality between the groups (P = 0.53, P = 0.57). There were no significant differences in any of the secondary outcomes. Conclusions MICU patients with severe CAP who received doxycycline versus azithromycin in addition to β-lactam treatment showed no significant differences in outcomes. These data offer support for inclusion of doxycycline as an alternative regimen in current IDSA recommendations.