Combination Therapy for Mycoplasma genitalium, and New Insights Into the Utility of parC Mutant Detection to Improve Cure.

Background: Mycoplasma genitalium (MG) infection is challenging to cure because of rising antimicrobial resistance and limited treatment options.
Methods: This was a prospective evaluation of the efficacy and tolerability of resistance-guided combination antimicrobial therapy for MG treatment at Melbourne Sexual Health Centre (August 2019-December 2020). All patients received 7 days of doxycycline before combination therapy based on the macrolide-resistant profile. Macrolide-susceptible infections received combination doxycycline + azithromycin (1 g, day 1; 500 mg, days 2-4) and macrolide-resistant infections combination doxycycline + moxifloxacin (400 mg daily for 7 days). Adherence and adverse effects were recorded at test-of-cure, recommended 14-28 days after antimicrobial completion. Sequencing was performed to determine the prevalence of single nucleotide polymorphisms (SNPs) in the parC gene and their association with moxifloxacin treatment outcomes in macrolide-resistant infections.
Results: Of 100 patients with macrolide-susceptible MG treated with doxycycline + azithromycin, 93 were cured (93.0%; 95% confidence interval [CI], 86.1-97.1). Of 247 patients with macrolide-resistant MG receiving doxycycline + moxifloxacin, 210 were cured (85.0%; 95% CI, 80.0-89.2). parC sequencing was available for 164 (66%) macrolide-resistant infections; 29% had SNPs at parC S83 or D87 (23% S83I). The absence of SNPs at parC S83/D87 was associated with 98.3% cure (95% CI, 93.9-99.8) following doxycycline + moxifloxacin. The presence of the parC S83I-SNP was associated with failure in 62.5% (95% CI, 45.8-77.3). Side effects were common (40%-46%) and predominantly mild and gastrointestinal.
Conclusions: Combination doxycycline + azithromycin achieved high cure for macrolide-susceptible infections. However, in the context of a high prevalence of the parC S83I mutation (23%) in macrolide-resistant infections, doxycycline + moxifloxacin cured only 85%. Infections that were wild-type for S83/D87 experienced high cure following doxycycline + moxifloxacin, supporting the use of a parC-resistance/susceptibility testing strategy in clinical care.
Competing Interests: Potential conflicts of interest. Melbourne Sexual Health Centre has received institutional funding to support research nurse salary time to support independent investigator-led research on Mycoplasma genitalium from Speedx Pty Ltd, and has received diagnostic kits from Speedx Pty Ltd, Hologic Pty Ltd, and Cepheid Pty Ltd. D. M. W. and J. S. J. report funding or support from SpeeDx Pty Ltd, Hologic Pty Ltd, and/or Cepheid Pty Ltd. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
(© The Author(s) 2022. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)