LAUSR

Introduction Resistance to 1 st (azithromycin) and 2nd line (moxifloxacin) therapy in Mycoplasma genitalium (MG) now exceeds 50% and 15%, respectively, in the Asia-Pacific region. New approaches to achieve high levels of cure and minimise resistance are urgently needed. We evaluated a novel strategy of switching from azithromycin to doxycycline for MG-associated syndromes and using resistance-guided therapy, with sitafloxacin for macrolide-resistant infections. Methods From July 2016 Melbourne Sexual Health Centre switched from azithromycin to doxycycline 100 mg twice daily 7 days for non-gonococcal urethritis/cervicitis/proctitis. Cases were tested for MG and macrolide-resistance mutations (MRM) by PCR (ResistancePlus MG test, SpeeDx Pty Ltd). After doxycycline, MG-positive cases without MRM received 2.5g azithromycin (1g then 500 mg daily for 3 days) and MRM-positive cases received sitafloxacin 100 mg twice daily for 7 days. Retest for microbiologic cure and standardised assessment of adherence, side-effects and post-diagnosis sexual contact occurred 14–90 days after the second antibiotic. Those reporting condomless sex or sex with an incompletely treated partner were excluded. Results Of 162 evaluable MG infections (35 women, 42 heterosexual men, 85 homosexual men, median age 29) diagnosed to 9 March 2017, MRM were detected in 116 [71.6% (95%confidence interval (CI) 64.0–78.4). Microbiologic cure occurred in: 44 of 46 infections without MRM, treated with doxycycline then azithromcyin [95.7% (95%CI 85.2–99.5)] and in 107 of 116 infections with MRM treated with doxycycline then sitafloxacin [92.2% (95%CI 85.8–96.4)]. Mean fall in log10 bacterial load (on doxycycline prior to the 2nd antibiotic, n=17) was 2.9, p<0.01. Sitafloxacin was associated with diarrhoea (8.6%) and tendon/joint pain (6.0%). Five (3.1%) patients missed >20% of doses of any antibiotic. Conclusion Switching from azithromycin to doxycycline for presumptive treatment of STI syndromes, and use of resistance-guided therapy cured >92% of MG infections in the context of high levels of antimicrobial resistance.