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Azithromycin antimicrobial resistance and genital Chlamydia trachomatis infection: duration of therapy may be the key to improving efficacy
  1. Paddy J Horner1,2
  1. 1School of Social and Community Medicine, University of Bristol, Bristol, UK
  2. 2Bristol Sexual Health Centre, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
  1. Correspondence to Dr Paddy J Horner, School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol BS8 2PS, UK; paddy.horner{at}

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A test of cure following treatment for uncomplicated cervical or urethral Chlamydia trachomatis infection with either single dose azithromycin (1 g) or doxycyline (100 mg twice daily for 7 days) is currently not recommended. Earlier trials indicated that both treatments are more than 95% effective.1–3 However, recent evidence strongly suggests that treatment failure may occur in more than 5% patients. This was the subject of a recent editorial by Handsfield4 and a late breaker symposium at the recent ISSTDR meeting in Quebec. Handsfield has argued persuasively that this apparent increase in treatment failure with azithromycin is probably not real. Tissue culture, which is less sensitive than nucleic acid amplification tests, was predominantly used in the original treatment trials and would not have been able to detect small numbers of persistent of C trachomatis bacteria.1 4 This article reviews the evidence for treatment failure, considers whether we need to modify current treatment regimes and suggests possible topics for future research.

It has always been assumed that individuals retesting positive for chlamydia after a full course of treatment may be due to re-infection.2 But, azithromycin treatment failures at levels >5% where re-infection has been excluded have been documented in women, men with non-gonococcal urethritis (NGU) and in men with rectal chlamydia. Two studies in women, not at risk of re-infection, have observed treatment failure rates of approximately 8%.5–7 A high failure rate (23%) was also recently observed in men with non-gonococcal urethritis treated with single dose azithromycin who were advised to abstain from sexual intercourse.8 Although re-infection could not be excluded, the doxycycline (100 mg twice daily for 7 days) group which did not differ in terms of sexual behaviour following treatment had a significantly lower failure rate (5.2%).4 8 In a retrospective study of …

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  • Competing interests None.

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