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Updated: Aug 16, 2025
Quantifying the Cytotoxicity of Staphylococcus aureus Against Human Polymorphonuclear Leukocytes
Published on: January 3, 2020
A Population-Based Evaluation of Polymicrobial Staphylococcus aureus Bacteremia
Joya-Rita Hindy1, Juan A Quintero-Martinez1, Brian D Lahr2
1Division of Public Health, Infectious Diseases and Occupational Health, Department of Medicine, College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
Objective:
To provide an evaluation of incidence and six-month mortality rates of polymicrobial Staphylococcus aureus bacteremia (p-SAB) in the United States (US).
Methods:
A retrospective population-based study of all incident adults with monomicrobial SAB (m-SAB) and p-SAB in Olmsted County, Minnesota (MN) from 1 January 2006, through 31 December 2020, was conducted. Demographics, clinical characteristics, in-hospital outcomes, and six-month survival were compared between groups.
Results:
Overall, 31 incident p-SAB cases occurred during the 15-year study period, corresponding to an overall age- and sex-standardized incidence rate of 1.9/100,000 person-years (95% CI, 1.3-2.6). One-third of p-SAB cases were due to MRSA, and almost one-half (15/31) were caused by Gram-positive bacteria. As compared to the 541 cases with incident m-SAB, p-SAB patients were more likely to have a catheter-related infection (p = 0.008) and less likely to be community-acquired cases (p = 0.027). The unadjusted risk of six-month mortality was greater in the p-SAB group (14/31, 45.2%) compared to the m-SAB group (144/541, 26.6%) (HR = 1.94, 95% CI = 1.12-3.36, p = 0.018). After adjusting for relevant covariates, this difference approached significance (HR = 1.93, 95% = CI 0.96-3.87, p = 0.064).
Conclusions:
To our knowledge, the current investigation represents the only US population-based study evaluating p-SAB patients. We found lower incidence rates for p-SAB than previously reported, with almost one-half of the cases caused by Gram-positive bacteria. Furthermore, these patients had poor survival compared to incident m-SAB cases.
Insights
Polymicrobial Staphylococcus aureus bacteremia (p-SAB) is less common than previously thought, with nearly half of cases caused by Gram-positive bacteria. Patients with p-SAB experienced significantly higher mortality rates compared to monomicrobial SAB.
Area of Science:
- Infectious Diseases
- Epidemiology
- Clinical Microbiology
Background:
- Staphylococcus aureus bacteremia (SAB) is a significant cause of morbidity and mortality.
- Polymicrobial SAB (p-SAB), involving S. aureus and other microorganisms, is less understood.
- Previous studies on p-SAB incidence and outcomes are limited, particularly in population-based settings.
Purpose of the Study:
- To determine the incidence rates of p-SAB in the United States.
- To evaluate the six-month mortality rates associated with p-SAB.
- To compare clinical characteristics and outcomes of p-SAB versus monomicrobial SAB (m-SAB).
Main Methods:
- A retrospective, population-based study was conducted in Olmsted County, Minnesota, from 2006 to 2020.
- Incident cases of m-SAB and p-SAB were identified and analyzed.
- Demographics, clinical data, in-hospital outcomes, and six-month survival were compared between p-SAB and m-SAB groups.
Main Results:
- The age- and sex-standardized incidence rate of p-SAB was 1.9 per 100,000 person-years.
- Nearly half of p-SAB cases (48.4%) were caused by Gram-positive bacteria; one-third involved MRSA.
- p-SAB patients were more likely to have catheter-related infections and less likely to be community-acquired compared to m-SAB patients.
- Unadjusted six-month mortality was higher in the p-SAB group (45.2%) than in the m-SAB group (26.6%).
Conclusions:
- This study provides the first US population-based evaluation of p-SAB, revealing lower incidence rates than previously reported.
- Gram-positive bacteria are a common cause of p-SAB.
- p-SAB is associated with poorer survival outcomes compared to m-SAB.
