Respiratory Virus Coinfection Is a Risk Factor for Adverse Outcomes During Staphylococcus aureus Bacteremia

We aimed to determine the impact of respiratory virus coinfection on clinical characteristics and outcomes of Staphylococcus aureus bacteremia (SAB).

We conducted an analysis within a retrospective observational cohort study of consecutive adults with monomicrobial SAB between 08/01/2021 and 29/12/2024 in Southeast Scotland. Variables were compared between patients tested/not tested for respiratory viruses, then between patients with/without coinfection detected. Survival was compared using Kaplan-Meier curves. Multiple logistic regression was used to identify independent risk factors for mortality.

We identified 651 patients with SAB during the study period; 64.5% (420/651) underwent polymerase chain reaction testing for respiratory viruses, 9.1% of whom (38/420) tested positive (severe acute respiratory syndrome coronavirus 2, n = 30; influenza A, n = 7; respiratory syncytial virus, n = 1). There were no differences in baseline characteristics between those testing positive vs negative for respiratory virus coinfection, including age, sex, Charlson Comorbidity Index, and quick Sequential Organ Failure Assessment score. Presence of coinfection was associated with a respiratory portal of entry of SAB, that is, bacteremic pneumonia (21.1% with coinfection vs 5.2% without coinfection; P = .002). Patients with respiratory virus coinfection had higher 30-day all-cause mortality (31.6% vs 18.0%; P = .04). Logistic regression identified that bacteremic pneumonia, but not viral coinfection itself, was independently associated with mortality. Mortality was not associated with receipt of immunomodulatory treatment of coronavirus disease 2019.

Respiratory virus coinfection is a risk factor for bacteremic S. aureus pneumonia, which is associated with increased 30-day mortality, independent of age, comorbidity, and receipt of immunomodulatory treatments.