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Background Previous viral pandemics have shown that secondary bacterial infections result in higher morbidity and mortality, with Staphylococcus aureus as the primary causative pathogen. The impact of secondary S. aureus bacteremia on mortality in patients infected with SARS-CoV-2 remains unknown. Methods This was a retrospective, observational case series of patients with COVID-19 disease who developed secondary S. aureus bacteremia across two New York City hospitals. The primary endpoint was to describe 14-day and 30-day hospital mortality rates of patients infected with COVID-19 and S. aureus bacteremia. Secondary endpoints included predictors of 14-day and 30-day hospital mortality in patients infected with COVID-19 and S. aureus bacteremia. Results A total of 42 hospitalized patients for COVID-19 with secondary S. aureus bacteremia were identified. Of these patients, 23 (54.8 %) and 28 (66.7%) died at 14 days and 30 days, respectively, from their first positive blood culture. Multivariate analysis identified hospital-onset bacteremia (≥4 days from date of admission) and age as significant predictors of 14-day hospital mortality, and Pitt bacteremia score as a significant predictor of 30-day hospital mortality (odds ratio [OR] 11.9 [95% confidence interval [CI] 2.03-114.7], p=0.01; (OR 1.10 [95% CI 1.03-1.20], p=0.02); and (OR 1.56 [95% CI 1.19-2.18], p=0.003), respectively. Conclusions Bacteremia with S. aureus is associated with high mortality rates in patients hospitalized with COVID-19 infection. Further investigation is warranted to understand the impact of COVID-19 and secondary S. aureus bacteremia.

Most infections by genus Bartonella in immunocompromised patients are caused by B. henselae and B. quintana. Unlike immunocompetent hosts who usually develop milder diseases such as cat scratch disease and trench fever, immunocompromised patients, including those living with HIV/AIDS and posttransplant patients, are more likely to develop different and severe life-threatening disease. This paper will discuss Bartonella's manifestations in immunosuppressed patients and will examine Bartonella's interaction with the immune system including its mechanisms of establishing infection and immune escape. Gaps in current understanding of the immunology of Bartonella infection in immunocompromised hosts will be highlighted.