Background: Mycoplasma genitalium is increasingly difficult to treat. Macrolide-resistance exceeds 50% in many regions, and the prevalence of fluoroquinolone resistance mutations is upwards of 20% in some regions of the Asia-Pacific, including Melbourne, Australia. Minocycline is an alternative treatment for patients with macrolide-resistant M. genitalium infections that have failed moxifloxacin and those with contraindications to fluoroquinolones. Data around the efficacy of minocycline for M. genitalium are limited to case reports and small series.
Methods: We conducted a retrospective review of patients with macrolide-resistant M. genitalium who were treated with minocycline 100mg BID for 14 days at Melbourne Sexual Health Centre (MSHC) between February 2020 - May 2022. Microbial cure was defined as a negative test-of-cure within 14-90 days after completing minocycline. The proportion cured with 95% confidence intervals (CI) were calculated and logistic regression was used to explore factors associated with treatment failure. To provide greater precision around microbial cure for minocycline, we pooled data from the current study with a prior juxtaposed case series of patients with M. genitalium who had received minocycline 100mg BID for 14 days at MSHC between May 2018 - February 2020.
Results: Data from 90 patients with macrolide-resistant M. genitalium who were treated with 14 days of minocycline were analysed; 60 patients (66.7% [95% CI 56.0%-76.3%]) experienced microbial cure within 14-90 days of completing minocycline. Adherence to minocycline was high; 86/90 patients (96%) reported taking all minocycline doses. Side-effects were mild and self-limiting, with dizziness/light-headedness being the most common side-effect reported (8/90, 8.9%). No demographic or clinical characteristics were associated with minocycline failure in regression analyses. In pooled analyses of 123 patients, 83 [67.5% (95% CI 58.4%-75.6%)] were cured following 14 days of minocycline.
Conclusion: Minocycline cured 68% of macrolide-resistant M. genitalium infections. These data provide tighter precision around the efficacy of minocycline for macrolide-resistant M. genitalium, and show that it is a well-tolerated regimen. With high levels of macrolide-resistance, increasing fluoroquinolone resistance, and the high cost of moxifloxacin, access to non-quinolone options such as minocycline is increasingly important for the clinical management of M. genitalium.
.jpg "Lenka A. Vodstrcil, PhD (she/her/hers) photo")