Open Access Highly Accessed Study protocol

A cohort study of Chlamydia trachomatis treatment failure in women: a study protocol

Jane S Hocking1*, Lenka A Vodstrcil12, Wilhelmina M Huston3, Peter Timms3, Marcus Y Chen14, Karen Worthington4, Ruthy McIver5, Sepehr N Tabrizi267 and on behalf of the Australian Chlamydia Treatment Study (ACTS) investigators

Author Affiliations

1 Melbourne School of Population and Global Health, University of Melbourne, Level 3, 207 Bouverie St, Carlton 3053, Victoria, Australia

2 Murdoch Children’s Research Institute, Parkville 3052, Victoria, Austrlaia

3 Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Ave, Kelvin Grove, Brisbane 4057, Queensland, Australia

4 Melbourne Sexual Health Centre, 580 Swanston Street, Carlton 3053, Victoria, Australia

5 Sydney Sexual Health Centre, Sydney Hospital, Macquarie Street, Sydney 2001, New South Wales, Australia

6 Department of Microbiology and Infectious Diseases, the Royal Women’s Hospital, Parkville 3052, Victorian, Australia

7 Department of Obstetrics and Gynaecology, University of Melbourne, Carlton 3053, Victoria, Australia

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BMC Infectious Diseases 2013, 13:379  doi:10.1186/1471-2334-13-379

Published: 17 August 2013



Chlamydia trachomatis is the most commonly diagnosed bacterial sexually transmitted infection in the developed world and diagnosis rates have increased dramatically over the last decade. Repeat infections of chlamydia are very common and may represent re-infection from an untreated partner or treatment failure. The aim of this cohort study is to estimate the proportion of women infected with chlamydia who experience treatment failure after treatment with 1 gram azithromycin.


This cohort study will follow women diagnosed with chlamydia for up to 56 days post treatment. Women will provide weekly genital specimens for further assay. The primary outcome is the proportion of women who are classified as having treatment failure 28, 42 or 56 days after recruitment. Comprehensive sexual behavior data collection and the detection of Y chromosome DNA and high discriminatory chlamydial genotyping will be used to differentiate between chlamydia re-infection and treatment failure. Azithromycin levels in high-vaginal specimens will be measured using a validated liquid chromatography – tandem mass spectrometry method to assess whether poor azithromycin absorption could be a cause of treatment failure. Chlamydia culture and minimal inhibitory concentrations will be performed to further characterize the chlamydia infections.


Distinguishing between treatment failure and re-infection is important in order to refine treatment recommendations and focus infection control mechanisms. If a large proportion of repeat chlamydia infections are due to antibiotic treatment failure, then international recommendations on chlamydia treatment may need to be re-evaluated. If most are re-infections, then strategies to expedite partner treatment are necessary.

Chlamydia trachomatis; Azithromycin; Treatment failure; Re-infection; Sexually transmitted infections