Polymicrobial Staphylococcus aureus bacteremia: Frequency, distinguishing characteristics and outcome
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Published on: April 19, 2024
Riad Khatib1, Mamta Sharma1, Leonard B Johnson1
1Department of Medicine, St John Hospital & Medical Center, Grosse Pointe Woods, MI, USA.
Abstract:
Staphylococcus aureus bacteremia (SAB) is usually monomicrobial (M-SAB). We reviewed SAB in adults (≥18years old) over a 13year-period and compared polymicrobial (P-SAB) and M-SAB. We encountered 93 P-SAB among 1537 SAB cases (6.1%). The source distribution was comparable; however, source-specified differences were apparent. P-SAB was noted in 12/58 (20.7%) necrotizing soft tissue infections/sacral decubiti and foot gangrene vs. 1/122 (0.8%) cellulitis/abscesses (P<0.001), in 7/64 (10.9%) femoral intravascular catheters (IVC) vs.16/376 (4.3%) IVC in other sites (P=0.03) and 15/134 (11.2%) healthcare-associated pneumonia (HAP) vs. 1/33 (3.0%) community-associated cases (P=0.1). Methicillin-resistance frequency was similar but community-associated SCCmec types (IV/V) were infrequent (17.9% vs. 34.2%; P=0.04). P-SAB was associated with higher mortality (50.5% vs. 24.2%; P<0.001) across nearly all sources. In summary, P-SAB is infrequent, usually encountered in necrotizing soft tissue infections/decubiti, femoral IVC and possibly HAP. The actual incidence of S. aureus in these infections should be defined.
Insights
Polymicrobial Staphylococcus aureus bacteremia (P-SAB) is uncommon, often linked to severe infections like necrotizing soft tissue infections and femoral catheters. P-SAB significantly increases mortality risk compared to monomicrobial cases.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Medicine
Background:
- Staphylococcus aureus bacteremia (SAB) is typically monomicrobial (M-SAB).
- Understanding polymicrobial SAB (P-SAB) is crucial for patient outcomes.
- Previous data on P-SAB incidence and characteristics are limited.
Purpose of the Study:
- To compare the incidence, sources, and outcomes of P-SAB versus M-SAB in adults.
- To identify specific clinical settings associated with P-SAB.
- To analyze the impact of polymicrobial involvement on mortality in SAB.
Main Methods:
- Retrospective review of adult SAB cases over a 13-year period.
- Comparison of P-SAB (93 cases) and M-SAB (1444 cases) based on clinical data.
- Analysis of infection sources, microbial characteristics, and mortality rates.
Main Results:
- P-SAB accounted for 6.1% of all SAB cases.
- P-SAB was significantly associated with necrotizing soft tissue infections/decubiti (20.7%), femoral intravascular catheters (10.9%), and healthcare-associated pneumonia (11.2%).
- P-SAB demonstrated a substantially higher mortality rate (50.5%) compared to M-SAB (24.2%).
Conclusions:
- Polymicrobial Staphylococcus aureus bacteremia is infrequent but associated with specific severe infections.
- P-SAB presents a significantly increased risk of mortality across various sources.
- Further investigation into the role of S. aureus in polymicrobial infections is warranted.
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