Recently, Mycoplasma genitalium (MG) has been reported to have developed antimicrobial resistance, which poses a therapeutic challenge. A systematic review and meta-analysis [1] published in 2020 summarizing the prevalence of genetic mutations associated with macrolide and fluoroquinolone resistance found that the prevalence of macrolide-resistant MG (MRM) was 35.5 %, up from 10.0 % before 2010. Fluoroquinolone-resistant MG (QRM) was found in 7.7 % of patients, and resistance to both macrolides and fluoroquinolones was observed in 2.8 %. A French surveillance conducted between 2018 and 2020 for QRM [2] showed a prevalence of 14.9–16.1 %.

Sequential therapy using doxycycline (DOX) followed by moxifloxacin (MXF) has been effective in the treatment of antimicrobial-resistant MG infections [3], especially MRM, and has been adopted in the guidelines [4,5]. Furthermore, a high cure rate has been reported for treatment-resistant MG with a combination of DOX and fluoroquinolone: 91.6 % (11/12) were cured with DOX plus sitafloxacin (STFX) [6] and 85.0 % (210/247) with DOX plus MXF [7].

However, treatment options for patients who are not cured with sequential or combination therapies are limited. Pristinamycin, a streptogramin-group antibiotic, has achieved a 75 % cure rate for MRM [8]; however, this drug is not available in Japan. Spectinomycin (SPT) is an antibiotic derived from aminocyclidine. It has been mainly used as a therapeutic agent for Neisseria gonorrhea infections [9]. In a case report, 2 g of SPT was administered intramuscularly once daily for 7 days to cure a MG infection [10]. To the best of our knowledge, there have been no subsequent reports on the effectiveness of spectinomycin against MG. At our hospital, spectinomycin has been used to treat difficult-to-treat MG infections that have not been cured by the aforementioned sequential or combination therapies after obtaining individual consent for off-label use. In this study, we evaluated the effectiveness of SPT for MG against such difficult-to-treat MG infections.