Background: Macrolide-resistance in Mycoplasma genitalium (MG) exceeds 50% in many regions and quinolone-resistance is increasing. We recently reported that resistance-guided therapy (RGT) using doxycycline followed by sitafloxacin or 2.5g-azithromycin cured 92% and 95% of macrolide-resistant and macrolide-susceptible infections, respectively. We now present the data on RGT using doxycycline-moxifloxacin, the regimen recommended in international guidelines, and extend the data on the efficacy of doxyxycline-2.5g azithromycin and subsequent de novo macrolide-resistance.
Methods: Patients attending Melbourne Sexual Health Centre between 2017-2018 with STI-related syndromes were treated with doxycycline for 7 days and recalled if positive for MG. Macrolide-susceptible cases then received 2.5g azithromycin (1g, then 500mg daily for 3 days) and resistant cases received moxifloxacin (400 mg daily, 7 days). Test of cure (TOC) was recommended 14-28 days post-completion of antimicrobials. Adherence and adverse effects were recorded.
Results: A total of 383 patients (81 females/106 heterosexual males/196 men-who-have-sex-with-men) were included. Microbial cure following doxycycline-azithromycin was 95.4% (95% CI 89.7-98.0) and doxycycline-moxifloxacin was 92.0%(88.1-94.6). De novo macrolide-resistance was detected in 4.6% of cases. Combining doxycycline-azithromycin data with our prior RGT study (n=186) yielded a pooled cure of 95.7% (91.6-97.8). ParC mutations implicated in moxifloxacin failure were present in 15-22% of macrolide-resistant cases at baseline.
Conclusion: These findings support the inclusion of moxifloxacin in resistance-guided strategies and extend the evidence for use of 2.5g azithromycin, and presumptive use of doxycycline. These data provide an evidence-base for current UK, Australian and European guidelines for the treatment of MG, an STI which is increasingly challenging to cure.
Keywords: Mycoplasma genitalium; antimicrobial resistance; moxifloxacin; sexually transmitted infections; treatment.
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