Abstract Background We aimed to determine the impact of respiratory virus co-infection on clinical characteristics and outcomes of S. aureus bacteraemia (SAB). Methods 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 South East Scotland. Variables were compared between patients tested/not tested for respiratory viruses, then between patients with/without co-infection detected. Survival was compared using Kaplan Meir curves. Multiple logistic regression was used to identify independent risk factors for mortality. Results We identified 651 patients with SAB during the study period. 64.5% (420/651) underwent PCR testing for respiratory viruses of which 9.1% (38/420) tested positive (SARS-CoV-2, n=30; influenza A, n=7; RSV, n=1). There were no differences in baseline characteristics between those testing positive vs. negative for respiratory virus co-infection, including age, sex, Charlson Comorbidity Index, and qSOFA score. Presence of co-infection was associated with a respiratory portal of entry of SAB, i.e. bacteraemic pneumonia (21.1% with co-infection vs. 5.2% without co-infection, p=0.002). Patients with respiratory virus co-infection had higher 30-day all-cause mortality (31.6% vs. 18.0%, p=0.04). Logistic regression identified that bacteraemic pneumonia, but not viral co-infection itself, was independently associated with mortality. Mortality was not associated with receipt of immunomodulatory treatment of Covid-19. Conclusions Respiratory virus co-infection is a risk factor for bacteraemic S. aureus pneumonia which is associated with increased 30-day mortality, independent of age, co-morbidity, and receipt of immunomodulatory treatments.
Roberts et al. (Fri,) studied this question.