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In-vitro activity of azithromycin and CP-63,956 against Treponema pallidum
1Department of Parasitology, School of Public Health, University of North Carolina, Chapel Hill 27599-7400.
Abstract:
The ability of the macrolide antibiotic azithromycin and its epimer CP-63,956 to inhibit protein synthesis in two pathogenic strains of Treponema pallidum was investigated. Using an in-vitro radiolabelling procedure employing treponemes freshly extracted from infected rabbit testes, our results indicate that both antibiotics were comparable with erythromycin in their ability to inhibit protein synthesis in T. pallidum Nichols strain. An erythromycin-resistant clinical isolate of T. pallidum, designated Street strain 14, exhibited only partial inhibition of protein synthesis at the highest antibiotic concentration tested.
Insights
Azithromycin and CP-63,956 effectively inhibit protein synthesis in Treponema pallidum. However, an erythromycin-resistant strain showed only partial inhibition, suggesting potential resistance mechanisms to macrolide antibiotics.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Treponema pallidum is a pathogenic bacterium responsible for syphilis.
- Macrolide antibiotics, such as erythromycin, are used to treat syphilis.
- Emergence of antibiotic resistance in T. pallidum poses a significant challenge to treatment efficacy.
Purpose of the Study:
- To investigate the efficacy of azithromycin and its epimer CP-63,956 in inhibiting protein synthesis in pathogenic Treponema pallidum strains.
- To compare the activity of these macrolides against both a standard strain and an erythromycin-resistant clinical isolate.
Main Methods:
- In vitro protein synthesis inhibition assay using radiolabelling.
- Treponemes were freshly extracted from infected rabbit testes.
- Tested azithromycin, CP-63,956, and erythromycin against T. pallidum Nichols strain and T. pallidum Street strain 14.
Main Results:
- Azithromycin and CP-63,956 demonstrated comparable inhibition of protein synthesis to erythromycin in the T. pallidum Nichols strain.
- The erythromycin-resistant T. pallidum Street strain 14 exhibited only partial inhibition, even at high antibiotic concentrations.
Conclusions:
- Azithromycin and CP-63,956 show potent in vitro activity against susceptible T. pallidum strains.
- The findings highlight the potential for erythromycin resistance in T. pallidum and suggest that azithromycin may also be affected in resistant strains.