August 12, 2015
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Efficacy of azithromycin against M. genitalium declines

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The efficacy of a single gram of azithromycin for the treatment of Mycoplasma genitalium appears to be decreasing over time, according to the results of a meta-analysis.

“Even though most of the evidence is based on data from observational studies that have considerable variability in sample size and timing of microbial cure, this low efficacy is of concern and is well below the 95% threshold recommended by WHO for STI treatments,” Andrew Lau, of the University of Melbourne, and colleagues wrote in Clinical Infectious Diseases. “However, given that the prevalence of resistance mutations is increasing, it is vital that new treatment regimens for [M. genitalium] are investigated.”

The researchers conducted an online systematic review and meta-analysis of Embase, Medline, PubMed and the Cochrane Central Register of Controlled Trials using search terms such as “M. genitalium” and “azithromycin.” Twenty-one studies, involving 1,490 participants, met inclusion criteria, the researchers wrote. Of these, 16 were observational trials, four were randomized trials and one was a controlled trial.

Based on study results, the random effects pooled microbial cure rate was 77.2% (95% CI, 71.1%-83.4%). The pooled microbial cure was 85.3% (95% CI, 82.3%-88.3%) for the 12 studies completed before 2009, while the pooled microbial cure for the remaining studies conducted since 2009 was 67% (95% CI, 57%-76.9%).

With the prevalence of resistant mutations increasing, it is critical to investigate new treatments for M. genitalium, according to Lau and colleagues.

“A major barrier to improving the management of [M. genitalium] is that the majority of M. genitalium infections are presumptively exposed to 1 g azithromycin during management of associated syndromes,” they wrote. “This raises the broader and more complex issue of whether it is now time to address the presumptive use of azithromycin in [M. genitalium]-associated syndromes.”

In a related editorial, Patrick J. Horner, MD, of the School of Social and Community Medicine, University of Bristol, suggested taking a sensible approach to addressing this issue.

“Given that the lack of widely available commercial test on which to base rational prescribing decisions for treating M. genitalium, we need to be pragmatic until this happens,” he said. “First, do no harm therefore seems a sensible approach.”

According to Horner, one option would be to recommend a regimen of 100 mg doxycycline twice daily for 7 days for the treatment of nongonococcal urethritis or cervicitis. Another option would be prescribing an extended azithromycin regimen of 1.5 g over 5 days, which is “greater than 95% effective and associated with low risk of inducing macrolide antimicrobial resistance, ie, harm is minimized.” – by Colleen Owens

Disclosures: Lau and colleagues report no relevant financial disclosures. Horner reports relationships with Aquarius Population Health, the British Association for Sexual Health and HIV, Cepheid, Crown Prosecution Service, Hologic and Mast Group, as well as a patent for a bacterial vaginosis test.