Microbial dynamics, risk factors and outcomes of secondary pneumonia in critically ill patients with COVID-19: A multicenter retrospective cohort study.

Background: Secondary pneumonia has a significant clinical impact on critically ill patients with COVID-19.
Aim: Considering potential geographic variations, this study explores the clinical implications of secondary pneumonia within East Asian populations.
Methods: This multicenter, retrospective cohort study enrolled critical COVID-19 patients requiring intensive care units (ICUs) admission in Taiwan from December 31, 2020, to June 1, 2022.
Findings: Among the 187 critical COVID-19 patients, 80 (42.8%) developed secondary pneumonia. The primary causative pathogens were gram-negative bacilli (GNB) (76.8%). Gram-positive cocci and fungi were mainly observed during the initial two weeks of ICU stay. Notably, the incidence of pulmonary aspergillosis was 9.2% during the first week of ICU stay and all Staphylococcus aureus were susceptible to methicillin. Multi-drug resistant organisms (MDROs) were responsible for 28.3% of the cases, exhibiting significantly longer ICU stays compared to the non-MDRO group (median, 27 vs. 14 days, P < 0.001). In the multivariate analysis, Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores were associated with a significantly increased risk of secondary pneumonia. In-hospital mortality was significantly higher in patients with secondary pneumonia than in those without (37.7% vs. 16.7%, P = 0.02) and survival analysis demonstrated gram-negative bacilli-related secondary pneumonia contributed to a worse prognosis.
Conclusion: Secondary pneumonia in critical COVID-19 patients significantly raised in-hospital mortality and extended hospital and ICU stays. Moreover, the presence of GNB notably predicted an unfavorable prognosis.
Competing Interests: Declaration of competing interest The authors declare that they have no competing interests.
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