Related Experiment Videos
Staphylococcus aureus mediastinitis and sternal osteomyelitis following median sternotomy in a rat model
Yoav Barnea1, Yehuda Carmeli, Boris Kuzmenko
1Division of Epidemiology and Laboratory for Molecular Epidemiology and Antimicrobials Research, Tel-Aviv Sourasky Medical Center, affiliated with the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
Objectives:
Median sternotomy (MS) wound infections are severe complications causing high morbidity and mortality after cardiac surgery. We aimed to develop a new Staphylococcus aureus mediastinitis and sternal osteomyelitis model in rats that can be used to evaluate the efficacy of new antimicrobial treatments.
Methods And Results:
A complete MS wound was induced in anaesthetized rats. S. aureus was injected into the sternum. Kinetics of bacterial growth in the sternum (10(7) cfu/sternum) was assessed for histopathology and bacterial counts. A non-infected MS group served as a control. To evaluate antibiotic efficacy, 5 days of intraperitoneal vancomycin therapy (50 mg/kg, twice a day) was initiated 24 h following bacterial challenge. Macroscopic and histological examination confirmed that infection resulted in sternitis and mediastinitis. S. aureus bacterial counts in the sternum were inoculum-dependent, and it was proven that infecting rats with an inoculum of 10(7) cfu/sternum induced mediastinitis and sternal osteomyelitis. At this inoculum, bacterial counts in the infected sternum increased with time, reaching a maximum level of 2 +/- 1 x 10(7) cfu/g of sternum 8-12 days post-infection and then decreased with time to 2 x 10(4) cfu/g of sternum 20 days after infection. Histological changes paralleled bacterial counts. Vancomycin administration showed a protective effect against induction of sternal osteomyelitis; sternums from vancomycin-treated rats showed a significant decrease in S. aureus counts by 0.72 +/- 0.35 log cfu/g compared with untreated controls (P = 0.0162).
Conclusions:
This new rat model of S. aureus sternal osteomyelitis and mediastinitis allows quantitative measurement of bacterial counts in the sternum. This model is reproducible and simple and thus suitable for the evaluation of new antimicrobials and new treatment modalities in MS infections.
Insights
A new rat model effectively simulates Staphylococcus aureus sternal osteomyelitis and mediastinitis after median sternotomy. This reproducible model aids in testing new antimicrobial treatments for these severe post-cardiac surgery infections.
Area of Science:
- Infectious Diseases
- Surgical Infections
- Animal Models
Background:
- Median sternotomy (MS) wound infections are serious complications following cardiac surgery.
- These infections lead to significant morbidity and mortality.
- There is a need for reliable models to test new treatments.
Purpose of the Study:
- To develop a novel rat model for Staphylococcus aureus mediastinitis and sternal osteomyelitis.
- To establish a reproducible system for evaluating antimicrobial efficacy.
Main Methods:
- A median sternotomy wound was created in rats, followed by direct injection of S. aureus into the sternum.
- Bacterial kinetics, histopathology, and osteomyelitis were assessed.
- Vancomycin treatment was administered to evaluate its efficacy.
Main Results:
- The model successfully induced sternitis, mediastinitis, and sternal osteomyelitis.
- Bacterial counts in the sternum were inoculum-dependent, with 10(7) cfu/sternum inducing the condition.
- Vancomycin treatment significantly reduced S. aureus counts in the sternum.
Conclusions:
- A reproducible and simple rat model for S. aureus sternal osteomyelitis and mediastinitis was developed.
- This model allows for quantitative bacterial assessment in the sternum.
- The model is suitable for evaluating new antimicrobials and treatment strategies for MS infections.