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Limited effect of trimethoprim-sulfamethoxazole prophylaxis on Pneumocystis carinii
Abstract:
Trimethoprim-sulfamethoxazole has been proven effective in the treatment and prevention of Pneumocystis carinii pneumonitis in lower animals and humans. How effective the drug combination is in eradicating P. carinii from the host is not known. The immunosuppressed rat model was used to determine whether or not trimethoprim-sulfamethoxazole effectively eradicated the organism. Animals treated with trimethoprim-sulfamethoxazole for as long as 6 weeks were then placed in individual isolator cages, immunosuppressed with prednisone for 12 weeks, and sacrificed. P. carinii was found in the lungs of at least 90% of the drug-treated as well as untreated control groups. The data indicate that trimethoprim-sulfamethoxazole has a limited rather than a lethal effect on P. carinii and that protection is afforded only during the period of trimethoprim-sulfamethoxazole administration.
Insights
Trimethoprim-sulfamethoxazole effectively prevents Pneumocystis pneumonia during treatment but does not eradicate Pneumocystis carinii from the host. The drug offers only temporary protection against this opportunistic infection.
Area of Science:
- Medical Microbiology
- Immunology
- Pharmacology
Background:
- Trimethoprim-sulfamethoxazole is known for treating and preventing Pneumocystis pneumonia.
- The efficacy of this drug combination in eradicating Pneumocystis carinii from hosts remains unclear.
Purpose of the Study:
- To investigate the eradicating effect of trimethoprim-sulfamethoxazole on Pneumocystis carinii in an immunosuppressed rat model.
Main Methods:
- An immunosuppressed rat model was utilized.
- Animals received trimethoprim-sulfamethoxazole for up to 6 weeks.
- Post-treatment, rats were immunosuppressed with prednisone for 12 weeks before sacrifice and examination.
Main Results:
- Pneumocystis carinii was detected in the lungs of over 90% of both drug-treated and untreated control groups.
- Trimethoprim-sulfamethoxazole demonstrated a limited, non-lethal effect on Pneumocystis carinii.
Conclusions:
- Trimethoprim-sulfamethoxazole provides protection against Pneumocystis carinii only during the administration period.
- The drug does not achieve complete eradication of Pneumocystis carinii from the host.