An antibiotic resistant experimental model of Pseudomonas osteomyelitis
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D R Nelson1, T B Buxton, Q N Luu
1VA Medical Center, Infectious Disease Laboratory, Augusta, GA 30910.
Abstract:
We report a model of chronic Pseudomonas aeruginosa osteomyelitis in the rat that was reproducible, simple and inexpensive. No promoting agent was required to cause infection. Infected animals yielded consistent pseudomonal colony counts (log): 4.98 +/- 0.32 (SD)/g cortical tibia (n = 16). The 95% confidence interval of the mean was 4.83-5.14. The inoculum required to infect 50% of challenged rats (ID50) was log 4.0; the ID 100 was log 6.4. Ceftazidime (50 mg/kg/8 h, subcutaneously), alone and in combination with tobramycin (40 mg/kg/12 h, subcutaneously), produced no significant change in quantitative bacterial count or gross bone pathology when used to treat established disease.
Insights
A reproducible rat model for chronic Pseudomonas aeruginosa osteomyelitis was developed. Antibiotic treatments with ceftazidime and tobramycin showed no significant effect on established infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Animal Models
Background:
- Chronic Pseudomonas aeruginosa osteomyelitis is a challenging infection.
- Developing reliable animal models is crucial for studying osteomyelitis.
- Existing models may lack reproducibility or be costly.
Purpose of the Study:
- To establish a simple, inexpensive, and reproducible rat model for chronic Pseudomonas aeruginosa osteomyelitis.
- To evaluate the efficacy of ceftazidime and tobramycin in treating established Pseudomonas aeruginosa osteomyelitis in this model.
Main Methods:
- Induction of Pseudomonas aeruginosa osteomyelitis in rats without a promoting agent.
- Quantitative bacterial counts (log colony-forming units per gram of cortical tibia) were determined.
- Infectious dose 50 (ID50) and infectious dose 100 (ID100) were calculated.
- Established infections were treated with ceftazidime alone or in combination with tobramycin.
Main Results:
- Consistent pseudomonal colony counts (log 4.98 ± 0.32 SD/g) were achieved in infected animals.
- The ID50 was log 4.0 and the ID100 was log 6.4.
- Treatment with ceftazidime and tobramycin did not significantly alter bacterial counts or bone pathology.
Conclusions:
- A reproducible and cost-effective rat model for chronic Pseudomonas aeruginosa osteomyelitis has been established.
- Current treatment regimens of ceftazidime and tobramycin are ineffective against established Pseudomonas aeruginosa osteomyelitis in this model.