Bacteraemia is a greater risk factor for death, intensive care unit admission, and mechanical ventilation than previously described risk factors for COVID-19 severity and mortality, such as advanced age, male sex, or various comorbidities. However, it has been unclear regarding the frequency of bacteremic co-infection in COVID-19 and the impact it has on clinical outcomes.
To understand this, the new study reviewed COVID-19 inpatient encounters at UAB Hospital and Ochsner Louisiana State University Health Shreveport hospitals and divided them into three groups: confirmed bacterial co-infection, as measured by a blood test at 48 hours after admission; suspected bacterial co-infection in patients receiving antimicrobials; and no bacterial co-infection.
Although confirmed bacteremic co-infections are rare in COVID-19, less than 4 percent of inpatient admissions, our results show that COVID-19 patients with these co-infections have a staggering 25 percent risk of death at 30 days in UAB patients and a similar risk of 20 percent.
Bacterial Co-Infection: Major Risk Factor for Death in COVID-19
These results strongly suggest an underappreciated interaction between bacterial pathogens and the COVID-19 virus, SARS-CoV-2, and their impact on clinical outcomes.
Specifically, the researchers found that the in-hospital mortality for COVID-19 co-infections of 26 percent at UAB and 22 percent at OLHS exceeded that of the suspected co-infection (UAB, 24 percent; OLHS, 12 percent) and the no co-infection groups (UAB, 5.9 percent; OLHS, 5.1 percent).
Furthermore, a control group of 1,703 UAB inpatients with community-acquired bacteremias during a period before the COVID-19 pandemic had a 5.9 percent in-hospital mortality rate.
They also identified laboratory trends associated with COVID-19 bacterial co-infection a neutrophil-to-lymphocyte ratio of 15 or greater, and the Systemic Inflammatory Response Syndrome, or SIRS, criteria of abnormal white blood cell counts or a heart rate greater than 90 beats per minute.
These results emphasize the role of bacteria in SARS-CoV-2 mortality and highlight the potential for neutrophil-to-lymphocyte ratio as a rapid and easily available prognostic biomarker of bacterial coinfection and, relatedly, disease severity.