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The combined effect of rifampin and pyrazinamide within the human macrophage
J A Sbarbaro1, M D Iseman, A J Crowle
1Department of Medicine/Division General Internal Medicine, School of Medicine, University of Colorado Health Sciences Center, Denver 80262.
Abstract:
A recent study in the murine model suggested that a combination of rifampin and pyrazinamide used as preventive therapy might shorten the duration of treatment time. Clinical trials using this combination have been initiated, but significant results will not be available for many years. The ex vivo human macrophage model has been instructive in expanding our knowledge of the activity of chemotherapeutic agents against intracellular virulent tubercle bacilli. Prior studies have shown rifampin to have a bactericidal effect in this model while even at clinically unachievable levels, pyrazinamide had only a bacteriostatic impact. This study finds an enhanced bacteriostatic effect when low, nonbactericidal levels of rifampin are combined with clinically achievable levels of pyrazinamide but not with higher bactericidal levels of rifampin. Adding pyrazinamide 2 days after the introduction of rifampin clearly enhanced the combined killing effect. However, reversing the order and adding rifampin 2 days after the introduction of pyrazinamide produced a result weaker than introducing the agents simultaneously. Our findings do not support the use of these agents as a potentially effective preventive therapy combination, but they suggest that the timing of the administration of these chemotherapeutic agents could be an important factor in their effectiveness.
Insights
This study investigated rifampin and pyrazinamide for tuberculosis treatment. Timing of administration significantly impacts the combined effect, suggesting potential for optimized therapeutic strategies.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Recent murine model studies suggested rifampin and pyrazinamide combination therapy could shorten tuberculosis treatment duration.
- Clinical trials are underway, but results are years away.
- The ex vivo human macrophage model is crucial for understanding anti-tubercular drug activity against intracellular bacteria.
Purpose of the Study:
- To evaluate the efficacy of combining rifampin and pyrazinamide against intracellular Mycobacterium tuberculosis in a human macrophage model.
- To determine if the timing of drug administration affects the combined bactericidal or bacteriostatic impact.
Main Methods:
- Utilized an ex vivo human macrophage model to assess the activity of rifampin and pyrazinamide.
- Investigated the effects of different concentrations and administration timings of rifampin and pyrazinamide.
Main Results:
- Low, non-bactericidal rifampin levels combined with achievable pyrazinamide levels showed enhanced bacteriostatic effects.
- Higher, bactericidal rifampin levels did not yield enhanced effects with pyrazinamide.
- Administering pyrazinamide 2 days after rifampin improved the combined killing effect.
- Reversing the order (rifampin after pyrazinamide) resulted in a weaker effect than simultaneous administration.
Conclusions:
- The findings do not support the combination of rifampin and pyrazinamide as a potentially effective preventive therapy.
- The timing of administration of rifampin and pyrazinamide is a critical factor influencing their effectiveness against tuberculosis.
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