Azithromycin Treatment Failure and Macrolide Resistance in Mycoplasma genitalium Infections in Sofia, Bulgaria

Abstract

Introduction: Mycoplasma genitalium is an established cause of sexually transmitted infections in men and women. Current guidelines recommend azithromycin and moxifloxacin as first- and second-line treatment, respectively. However, azithromycin treatment failure has been increasingly reported. The aim of this study was to determine the efficacy of azithromycin and alternative antibiotic regimens in a prospective cohort of M. genitalium-positive patients, and macrolide resistance mutations associated with azithromycin failure. Materials and methods: Consecutive eligible M. genitalium-positive patients attending the National Center of Infectious and Parasitic Diseases in Sofia, Bulgaria between 1 January 2018 and 31 December 2020 were treated with azithromycin and retested by polymerase chain reaction 21-28 days after completion of the treatment. Cure was defined as M. genitalium-negative result on the test of cure. Cases failing azithromycin were treated with moxifloxacin and retested another 21-28 days after treatment. Pre- and post-treatment samples were assessed for macrolide resistance mutations by conventional DNA sequencing. Results: Of 21 patients treated with azithromycin, 11 (52.4%) were cured. Pre- and post-treatment macrolide resistance mutations were detected in 10 (47.6%) patients, and all of them failed azithromycin. Moxifloxacin was effective in all cases failing azithromycin; and all were M. genitalium-negative at the test of cure after moxifloxacin treatment. Conclusions: In this study a high azithromycin failure rate (47.6%) in an M. genitalium-positive cohort in association with high levels of pretreatment macrolide resistance was reported. Moxifloxacin was highly effective in treating macrolide-resistant infections. These findings necessitate implementation of new diagnostic and therapeutic strategies such as sequential antimicrobial therapy for M. genitalium guided by a macrolide-resistance assay.