Therapeutic efficacy of lascufloxacin in patients with <i>Mycoplasma pneumoniae</i> pneumonia

The prevalence of macrolide-resistant <i>Mycoplasma pneumoniae</i> in Japan is increasing once again. This study compared the therapeutic efficacy of fluoroquinolone lascufloxacin with minocycline, the recommended first-choice drug for patients with macrolide-resistant <i>M. pneumoniae</i> pneumonia. A prospective observational study was conducted at 12 facilities affiliated with Kansai Medical University Hospital, investigating patients with <i>M. pneumoniae</i> pneumonia between January 2024 and January 2025. Of the 93 patients with <i>M. pneumoniae</i> pneumonia, 51 (54%) were found to be infected with macrolide-resistant <i>M. pneumoniae</i>. All of these patients had an A-to-G transition at position 2063 in domain V of the 23S rRNA gene, resulting in high-level resistance to macrolides. Of the 33 patients with macrolide-sensitive <i>M. pneumoniae</i> pneumonia, 91% and 90% of patients experienced defervescence within 48 hours of initiating antibiotics with lascufloxacin and minocycline, respectively. Among the 42 patients with macrolide-resistant <i>M. pneumoniae</i> pneumonia, 90% of those in the lascufloxacin group and 90% of those in the minocycline group experienced defervescence within 48 hours of starting antibiotics. No antibiotic changes were recorded for patients in either group. Our results demonstrate that lascufloxacin may be an effective treatment for macrolide-resistant <i>M. pneumoniae</i> pneumonia, even in highly resistant strains. Physicians may consider using lascufloxacin or minocycline instead of macrolides when macrolide-resistant <i>M. pneumoniae</i> pneumonia is suspected and defervescence does not occur within 48 hours of starting macrolide treatment.IMPORTANCESince the isolation of macrolide-resistant <i>Mycoplasma pneumoniae</i> in 2000, resistant strains have spread rapidly across East Asia. In Japan, the prevalence rate of macrolide-resistant <i>M. pneumoniae</i> has decreased since peaking in 2012. Nevertheless, 80-100% of <i>M. pneumoniae</i> strains in East Asia have become macrolide-resistant. Consequently, it was predicted that the number of macrolide-resistant strains would rise again in Japan. The Japanese Society of Mycoplasmology, therefore, recommended minocycline as the antibiotic of choice for treating macrolide-resistant <i>M. pneumoniae</i> pneumonia. Drug susceptibility to <i>M. pneumoniae</i> differs among respiratory quinolones, and the clinical efficacy of tosufloxacin, which has a high minimum inhibitory concentration, is inferior. Therefore, differences in efficacy may exist among respiratory quinolones. In this study, we investigated the therapeutic efficacy of lascufloxacin in patients with macrolide-resistant <i>M. pneumoniae</i> pneumonia, confirming that it was equally effective as minocycline.