Treponema pallidum macrolide resistance in BC

Department of Pathology and Laboratory Medicine, University of British Columbia - Vancouver, Vancouver, British Columbia, Canada
Canadian Medical Association Journal (Impact Factor: 5.96). 02/2006; 174(3):349. DOI: 10.1503/cmaj.1050256
Source: PubMed
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    ABSTRACT: To determine whether the 23S rRNA mutation that confers macrolide resistance is present in >1 Treponema pallidum strain, 58 isolates collected between 2001 and 2005 were screened for this mutation and for an unrelated sequence that distinguishes between strains. The odds of identifying a macrolide-resistant strain increased over time (P=.006). In subjects who had received macrolides in the previous year, the relative risk of harboring a resistant strain was 2.2 (95% confidence interval, 1.1-4.4; P=.02). The macrolide-resistant strains were not identical. These findings suggest that macrolide resistance may be increasing in multiple strains in response to antibiotic pressure.
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    ABSTRACT: Although the recommended treatment for syphilis is penicillin, azithromycin has been used as an alternative. We discuss azithromycin-related treatment failures and resistance in Treponema pallidum, and propose ways to meet the resulting clinical and public health challenges. Azithromycin treatment failures in syphilis were first noted in San Francisco in 2002 and result from an A-->G mutation at position 2058 of the 23S rRNA gene of T. pallidum. This mutation confers resistance by precluding macrolide binding to the bacterial 50S ribosomal subunit, of which 23S rRNA is a structural component. Azithromycin resistance has also been identified in T. pallidum specimens from elsewhere in the United States, Ireland, and Canada, and the amount of resistant specimens has increased with time. Treatment with azithromycin or other macrolides appears to be a risk factor for presenting with a resistant T. pallidum strain. Although T. pallidum remains sensitive to penicillin and certain other antibiotics, azithromycin resistance in T. pallidum has emerged and is increasing in the United States, Canada, and Ireland. This poses clinical and public health challenges, and indicates a need for further antibiotic drug development and surveillance for resistance in T. pallidum. If azithromycin is used to treat syphilis, clinicians and public health practitioners should remain vigilant for treatment failures.
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