Bacterial Coinfection and Superinfection in Respiratory Syncytial Virus-Associated Acute Respiratory Illness: Prevalence, Pathogens, Initial Antibiotic-Prescribing Patterns and Outcomes.

We aimed to determine the prevalence of bacterial coinfection (CoBact) and bacterial superinfection (SuperBact), the causative pathogens, the initial antibiotic-prescribing practice, and the associated clinical outcomes of hospitalized patients with respiratory syncytial virus-associated acute respiratory illness (RSV-ARI). This retrospective study included 175 adults with RSV-ARI, virologically confirmed via RT-PCR, during the period 2014-2019. Thirty (17.1%) patients had CoBact, and 18 (10.3%) had SuperBact. The independent factors associated with CoBact were invasive mechanical ventilation (OR: 12.1, 95% CI: 4.7-31.4; p < 0.001) and neutrophilia (OR: 3.3, 95% CI: 1.3-8.5; p = 0.01). The independent factors associated with SuperBact were invasive mechanical ventilation (aHR: 7.2, 95% CI: 2.4-21.1; p < 0.001) and systemic corticosteroids (aHR: 3.1, 95% CI: 1.2-8.1; p = 0.02). CoBact was associated with higher mortality compared to patients without CoBact (16.7% vs. 5.5%, p = 0.05). Similarly, SuperBact was associated with higher mortality compared to patients without SuperBact (38.9% vs. 3.8%, p < 0.001). The most common CoBact pathogen identified was Pseudomonas aeruginosa (30%), followed by Staphylococcus aureus (23.3%). The most common SuperBact pathogen identified was Acinetobacter spp. (44.4%), followed by ESBL-positive Enterobacteriaceae (33.3%). Twenty-two (100%) pathogens were potentially drug-resistant bacteria. In patients without CoBact, there was no difference in mortality between patients who received an initial antibiotic treatment of <5 days or ≥5 days.