Introduction To determine the efficacy of pristinamycin-based regimens for M. genitalium-infections failing prior regimens and to examine the presence of 23S rRNA and ribosomal protein gene mutations and their association with treatment failure.
Methods In 2013 M. genitalium-infected men and women attending Melbourne Sexual Health Centre who failed azithromycin and moxifloxacin were treated with pristinamycin 1g qid for 10 days with a test-of-cure (TOC) 3–4 weeks post-pristinamycin. From December 2014 pristinamycin was prescribed 1g bid for 10 days second-line following azithromycin failure. Pre- and post-treatment samples were stored and sequenced to detect 23S rRNA and ribosomal protein gene mutations, as potential markers of pristinamycin resistance.
Results By March 2015 37 M. genitalium-infected patients had received pristinamycin: 32 males (10 rectal; 22 urine samples) and 5 females (1 rectal; 3 urine; 1 cervical). TOC data are available on 25 patients at abstract submission: 20 were cured (80%; 95% CI 61–92%) and 5 (20%; 8–39%) failed pristinamycin. Failure rates in the 16 patients treated with 1g qid 10 days were 12% (n = 2), and 33% (n = 3) in the 9 treated with 1g bd 10 days, p = 0.23. Of the 5 pristinamycin failures; 2 were cured with moxifloxacin, 3 failed moxifloxacin and are awaiting TOCs following solithromycin or combined doxycycline/pristinamycin. Mutations in 23S rRNA and ribosomal protein genes were associated with failure of pristinamycin.
Conclusion Increasing reports of azithromycin and moxifloxacin failure for M. genitalium-infections necessitates evaluation of new agents. We present some of the earliest data on the use of pristinamycin for M. genitalium. Treatment failure occurred when delivered as monotherapy following failure of prior regimens. Current data on use of combined pristinamycin and doxycycline as a second line regimen after azithromycin failure will be available for presentation. Resistance mutations in the 23S rRNA and ribosomal protein genes are associated with pristinamycin failure.
Disclosure of interest statement No pharmaceutical grants were received in the development of this study.