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Macrolide resistance testing and molecular subtyping of Treponema pallidum strains from southern Africa
  1. Etienne E Müller1,
  2. Gabriela Paz-Bailey2,
  3. David A Lewis1,3,4
  1. 1Centre for HIV and Sexually Transmitted Infections, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
  2. 2Center for Health Studies, Del Valle University of Guatemala, Guatemala City, Guatemala
  3. 3Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
  4. 4Division of Medical Microbiology, University of Cape Town, Cape Town, South Africa
  1. Correspondence to Dr Etienne E Müller, Centre for HIV and Sexually Transmitted Infections, National Institute for Communicable Diseases, National Health Laboratory Service, Private Bag X4, Sandringham, Johannesburg 2131, South Africa; etiennem{at}


Objectives To determine whether the 23S ribosomal RNA (rRNA) A2058G and A2059G mutations that confer macrolide resistance are present among southern African strains of Treponema pallidum and to determine their subtype distribution.

Methods 117 genital ulcer specimens, collected between March 2005 and April 2010 in South Africa and Lesotho and previously determined to be positive for T pallidum DNA by molecular testing, were retested using a commercial real-time PCR assay. Those specimens that were still positive for T pallidum DNA were screened for the macrolide resistance-encoding point mutations in the 23S rRNA gene using rapid PCR-based restriction digest assays. Molecular characterisation of two variable treponemal genes, arp and tpr, was used to subtype the T pallidum strains.

Results 1 of 100 T pallidum-positive specimens, collected in Lesotho, contained the A2058G macrolide resistance-encoding 23S rRNA gene mutation, whereas the A2059G mutation was absent. It was possible to fully type 97/100 of all T pallidum DNA-positive samples. A total of nine arp repeat sizes, nine tpr patterns and a combined total of 20 subtypes were identified. Overall, the most common subtypes were 14d (32%), followed by 17d (12%), 14a (10%), 14b (8%), 22b (6%) and 14i (5%). Subtypes 14d and 14a were the predominant subtypes in samples from South Africa (43%) and Lesotho (22%), respectively.

Conclusions Macrolide resistance among T pallidum strains appears to be uncommon in southern Africa. Although a high degree of genetic heterogeneity was observed among the strains tested, T pallidum subtype 14d appears to be the predominant circulating strain.

  • Syphilis
  • azithromycin
  • antibiotic resistance
  • molecular typing
  • Africa
  • molecular technique
  • viral isolation
  • cervical cancer
  • LGV
  • STDs
  • epidemiology (general)
  • genital ulcers
  • herpes
  • surveillance
  • HIV

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  • Funding This research was funded by the National Health Laboratory Service Research Trust, the National Health Laboratory Service, South Africa. Twenty-five of the samples tested in this study were obtained either from men recruited in an episodic herpes treatment study (HSV 4294) or from national microbiological surveillance conducted in 2006/2007 in Kimberley and Johannesburg. Both of these activities were funded through by cooperative agreement number U62/CCU022901 from the Centres for Disease Control and Prevention (CDC), Atlanta, USA. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Department of Health and Human Services at the CDC and the National Centre for Global AIDS Prevention (NCHSTP).

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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