Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Abstract Background Although cases of respiratory bacterial infections associated with coronavirus disease 2019 (COVID-19) have often been reported, their impact on the clinical course remains unclear. Herein, we evaluated and analyzed the complication rates of bacterial infections, causative organisms, patient backgrounds, and clinical outcome in Japanese patients with COVID-19. Methods We performed a retrospective cohort study that included inpatients with COVID-19 from multiple centers participating in the Japan COVID-19 Taskforce (April 2020 to May 2021) and obtained demographic, epidemiological, and microbiological results and the clinical course and analyzed the cases of COVID-19 complicated by respiratory bacterial infections. Results Of the 1,863 patients with COVID-19 included in the analysis, 140 (7.5%) had respiratory bacterial infections. Community-acquired co-infection at COVID-19 diagnosis was uncommon (55/1,863, 3.0%) and was mainly caused by Staphylococcus aureus, Klebsiella pneumoniae and Streptococcus pneumoniae. Hospital-acquired bacterial secondary infections, mostly caused by Staphylococcus aureus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia, were diagnosed in 86 patients (4.6%). Severity-associated comorbidities were frequently observed in hospital-acquired secondary infection cases, including hypertension, diabetes, and chronic kidney disease. The study results suggest that the neutrophil–lymphocyte ratio (> 5.28) may be useful in diagnosing complications of respiratory bacterial infections. COVID-19 patients with community-acquired or hospital-acquired secondary infections had significantly increased mortality. Conclusions Respiratory bacterial co-infections and secondary infections are uncommon in patients with COVID-19 but may worsen outcomes. Assessment of bacterial complications is important in hospitalized patients with COVID-19, and the study findings are meaningful for the appropriate use of antimicrobial agents and management strategies

Additional file 6 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 6. Admission to intensive care unitand use of invasive mechanical ventilationof bacterial respiratory infection with coronavirus disease 2019

Additional file 1 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 1. Identification of organisms in ventilator-associated pneumoniacase

Additional file 4 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 4. Details of respiratory secondary infection

Additional file 5 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 5. Association of anti-IL-6 receptor antibody use with incidence of secondary infection and death

Additional file 8 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 8. Proportion of thrombosis and myocardial injury in bacterial respiratory co-infection and secondary infection with coronavirus disease 2019

Additional file 2 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 2. Evaluation of white blood cells, neutrophils, lymphocytes, neutrophil-lymphocyte ratio, C-reactive protein, and procalcitonin on admission as predictors of respiratory bacterial co-infection based on the area under the curv

Additional file 7 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 7. Forest plot of adjusted oddsratios by multivariate logistic regression analysis of risk factors of death in patients of coronavirus disease 2019with secondary infection except ventilator-associated pneumoniaand VAP

Additional file 3 of Impact of respiratory bacterial infections on mortality in Japanese patients with COVID-19: a retrospective cohort study

Additional file 3. Neutrophil-lymphocyte ratioas a predictor of co-infection in steroid and non-steroid user