Risk factors and outcomes of severe influenza pneumonia with bacterial co-infection in critically ill patients

Introduction: Bacterial co-infection in influenza infection was reported to be around 18-34% and associated with high mortality. We aim to investigate the risk factors and clinical impact of bacterial co-infection in critically ill influenza pneumonia in Taiwan. Methods: We retrospectively reviewed adult patients who admitted to intensive care units (ICUs) due to influenza pneumonia during the pandemic period (from January 2016 to April 2016) in three hospitals. We compared the cases with and without bacterial co-infection and analyzed the associated clinical outcomes. Results: A total 136 adult patients admitted to ICUs with a diagnosis of influenza infection were screened and 43 patients were excluded with negative result of influenza test. We studied 93 patients (83.8% influenza A and 16.1% influenza B); the overall mean age was 62 + 15 years, 60.2% of patients were male and 27.8% had initial bacterial co-infection. Predictive risk factors for bacterial co-infection were chronic respiratory diseases (Odds Ratio [OR]:7.374), chronic cardiovascular diseases (OR: 4.415), male patient (OR: 4.206) and lower body weight (OR:1.094). The most frequent pathogens were Klebsiella pneumonia (26.9%), Staphylococcus aureus (MSSA) (23.1%) and Pseudomonas aeruginosa (15.4%). In comparison with patients without bacterial co-infection, patients with bacterial co-infection had relatively higher ICU mortality, 28 days mortality and hospital mortality. Conclusions: Bacterial co-infection was common in critically ill influenza pneumonia patients with higher mortality rate. Thin, male patients with chronic heart-lung disease as the main predictive risk factors.