Evaluation of treatment with two weeks of doxycycline on macrolide-resistant strains of Mycoplasma genitalium: a retrospective observational study

Increasing macrolide resistance makes treatment of Mycoplasma genitalium infections challenging. The second-line treatment is moxifloxacin, an antibiotic drug best avoided due to the potential of severe side effects and interactions. This study evaluates the effects of treatment with doxycycline 100 mg twice daily for 2 weeks as an alternative to moxifloxacin. This retrospective observational study examined the medical records of patients testing positive for macrolide resistant Mycoplasma genitalium from January 1st, 2016 to September 1st, 2019 in Trondheim, Norway. Information regarding symptoms as well as clinical and microbiological cure was collected. 263 infections from 259 patients (161 females/98 males) were examined. 155 (58.9%) had a negative test of cure following treatment. 34.7% of symptomatic patients not achieving microbiological cure experienced symptom relief or clearance. There was no statistical difference between bacterial loads in symptomatic versus asymptomatic patients. The mean difference was 1.6 × 10 copies/ml (95% CI - 1.4 × 10 -4.8 × 10 , p = 0.30) for women and 1.4 × 10 copies/ml (95% CI -4.0 × 10 -3.2 × 10 , p = 0.12) for men. The cure rate of doxycycline in this study is higher than previously reported. This adds support to doxycycline's role in treatment before initiating treatment with less favorable drugs such as moxifloxacin.