Incidence and risk factors for clinically confirmed secondary bacterial infections in patients hospitalized for coronavirus disease 2019 (COVID-19)

OBJECTIVE: The true incidence and risk factors for secondary bacterial infections in coronavirus disease 2019 (COVID-19) remains poorly understood. Knowledge of risk factors for secondary infections in hospitalized patients with COVID-19 is necessary to optimally guide selective use of empiric antimicrobial therapy. DESIGN: Single-center retrospective cohort study of symptomatic inpatients admitted for COVID-19 from April 15, 2020, through June 30, 2021. SETTING: Academic quaternary-care referral center in Portland, Oregon. PATIENTS: The study included patients who were 18 years or older with a positive severe acute respiratory coronavirus virus 2 (SARS-CoV-2) PCR test up to 10 days prior to admission. METHODS: Secondary infections were identified based on clinical, radiographic, and microbiologic data. Logistic regression was used to identify risk factors for secondary infection. We also assessed mortality, length of stay, and empiric antibiotics among those with and without secondary infections. RESULTS: We identified 118 patients for inclusion; 31 (26.3%) had either culture-proven or possible secondary infections among hospitalized patients with COVID-19. Mortality was higher among patients with secondary infections (35.5%) compared to those without secondary infection (4.6%). Empiric antibiotic use on admission was high in both the secondary and no secondary infection groups at 71.0% and 48.3%, respectively. CONCLUSIONS: The incidence of secondary bacterial infection was moderate among hospitalized patients with COVID-19. However, a higher proportion of patients received empiric antibiotics regardless of an identifiable secondary infection. Transfer from an outside hospital, baseline immunosuppressant use, and corticosteroid treatment were independent risk factors for secondary infection. Additional studies are needed to validate risk factors and best guide antimicrobial stewardship efforts.