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Published on: February 2, 2024
Beyond Gram-Negative and Gram-Positive Bacteria: Virulence as a Determinant of Clinical Outcome in Periprosthetic
Veronika Achatz1, Sujeesh Sebastian2, Jennyfer A Mitterer3
1Michael Ogon Laboratory for Orthopaedic Research, Orthopaedic Hospital Speising, Vienna, Austria; Department of Orthopaedics and Trauma, Medical University of Graz, Graz, Austria.
Background:
Gram-negative (GN) periprosthetic joint infections (PJIs) are still less frequent than gram-positive (GP) PJIs. There is only little data available on a direct comparison of GP- and GN-associated PJIs. Therefore, we investigated the outcome of GN and GP hip and knee PJI according to the virulence of the pathogens in a matched cohort.
Methods:
We retrospectively evaluated 1,695 culture-positive revision hip and knee arthroplasties from a single institution performed between 2008 and 2024. Infection-confirmed PJIs, according to the European Bone and Joint Infection Society criteria, were included. Polymicrobial cases with mixed GN and GP pathogens and anaerobic infections were excluded. A 1:3 propensity score matching for Charlson Comorbidity Index, age, sex, hip, and knee was performed using logistic regressions. The GP PJIs were divided into low (150 of 252; 59.5%) and high-virulent pathogens (102 of 252; 40.5%). Outcomes were determined using the Tier classification by the Musculoskeletal Infection Society.
Results:
The GN PJIs demonstrated a significantly worse outcome than GP PJIs (P = 0.032) and a 1.64-fold higher risk of reinfection. High-virulent GN/GP PJIs have shown a significantly worse outcome than low-virulent PJIs. There was no statistical significance identified when comparing high-virulent GP PJIs and GN PJIs (P = 0.73). In GN PJIs, single-stage procedures showed the highest success rate (62.5%), whereas debridement, antibiotics, and implant retention showed the lowest (30.8%). Resistance to fluoroquinolones was observed in up to 24% of GN pathogens. However, treatment with fluoroquinolones did not result in a higher success rate (P = 0.214).
Conclusions:
To our knowledge, this is the first study comparing GN PJIs and GP PJIs based on their virulence, demonstrating that GN PJIs have a significantly worse outcome than GP PJIs. However, high-virulent GP PJIs have shown the same outcome as GN PJIs, suggesting that virulence plays an equally important role in determining the outcome of PJIs.
Insights
Gram-negative periprosthetic joint infections (PJIs) show worse outcomes than Gram-positive PJIs, with a higher reinfection risk. Pathogen virulence significantly impacts PJI outcomes, with high-virulence strains yielding similar results to Gram-negative infections.
Area of Science:
- Orthopedic Surgery
- Infectious Diseases
- Microbiology
Background:
- Periprosthetic joint infections (PJIs) are complications of joint replacement surgery.
- Gram-negative (GN) PJIs are less common but poorly understood compared to Gram-positive (GP) PJIs.
- Limited data exists on direct comparisons between GP and GN PJIs, especially considering pathogen virulence.
Purpose of the Study:
- To compare the outcomes of GN and GP hip and knee PJIs.
- To evaluate the influence of pathogen virulence on PJI treatment success.
- To identify factors affecting PJI outcomes in a matched cohort.
Main Methods:
- Retrospective analysis of 1,695 culture-positive revision hip and knee arthroplasties (2008-2024).
- Inclusion of infection-confirmed PJIs based on European Bone and Joint Infection Society criteria.
- Exclusion of polymicrobial and anaerobic infections; 1:3 propensity score matching for patient factors and procedure type.
- Categorization of GP PJIs into low and high-virulence groups; outcome assessment using Musculoskeletal Infection Society Tier classification.
Main Results:
- GN PJIs had significantly worse outcomes and a 1.64-fold higher reinfection risk compared to GP PJIs (P=0.032).
- High-virulence GN/GP PJIs showed worse outcomes than low-virulence PJIs; no significant difference between high-virulence GP and GN PJIs (P=0.73).
- In GN PJIs, single-stage procedures had the highest success rate (62.5%), while debridement, antibiotics, and implant retention had the lowest (30.8%). Fluoroquinolone resistance was up to 24%, but fluoroquinolone treatment showed no improved success rate (P=0.214).
Conclusions:
- GN PJIs are associated with significantly worse outcomes than GP PJIs.
- Pathogen virulence is a critical factor in PJI outcomes, comparable in impact to the bacterial type (GN vs. GP).
- High-virulence GP PJIs demonstrated similar outcomes to GN PJIs, highlighting the importance of virulence in treatment strategies.
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