Incidence, risk factors and outcomes of healthcare-associated bacterial infections in COVID-19 patients receiving respiratory support: a retrospective cohort study

Objective The aim of the present study was to assess the incidence, risk factors and outcomes of bacterial healthcareassociated infections (HAIs) in COVID-19 patients receiving respiratory support. Methods This retrospective study included COVID-19 hospitalised patients requiring either invasive or non-invasive respiratory support at the ASST Santi Paolo e Carlo in Milan (Italy) from September 2020 to December 2021. Data on demographics, clinical and laboratory findings, and outcomes were extracted from electronic health records. The cumulative incidence rate of a first HAI episode was evaluated by cumulative incidence function. Risk factors for bacterial HAIs and their association with in-hospital mortality were analysed using Fine-Gray proportional hazard models. Results Among 744 patients, 118 (15.9%) developed at least one bacterial HAI during respiratory support, mostly caused by Gram-negative bacteria. The cumulative incidence of HAIs was 15.7% by 30 days, and significantly higher in intensive care unit (ICU) settings compared to medical/surgical units (MSUs). Independent risk factors for HAIs were male sex [adjusted subhazard ratio (aSHR) 2.29, 95% CI 1.39–3.78], ICU stay (aSHR 7.61, 95% CI 3.32–17.43), and therapy with biological drugs (aSHR 2.11, 95% CI 1.05–4.23). HAIs were associated with an increased risk of in-hospital mortality (aSHR 2.06, 95% CI 1.44–2.96), with both pneumonias and bloodstream infections contributing significantly to mortality. Conclusions Bacterial HAIs are common in COVID-19 patients on respiratory support, especially in ICU settings, and are associated with increased mortality.