Tosufloxacin Tosilate Hydrate

The prevalence of macrolide-resistant Mycoplasma pneumoniae 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 M. pneumoniae pneumonia. A prospective observational study was conducted at 12 facilities affiliated with Kansai Medical University Hospital, investigating patients with M. pneumoniae pneumonia between January 2024 and January 2025. Of the 93 patients with M. pneumoniae pneumonia, 51 (54%) were found to be infected with macrolide-resistant M. pneumoniae . 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 M. pneumoniae 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 M. pneumoniae 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 M. pneumoniae pneumonia, even in highly resistant strains. Physicians may consider using lascufloxacin or minocycline instead of macrolides when macrolide-resistant M. pneumoniae pneumonia is suspected and defervescence does not occur within 48 hours of starting macrolide treatment.

Since the isolation of macrolide-resistant Mycoplasma pneumoniae in 2000, resistant strains have spread rapidly across East Asia. In Japan, the prevalence rate of macrolide-resistant M. pneumoniae has decreased since peaking in 2012. Nevertheless, 80–100% of M. pneumoniae 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 M. pneumoniae pneumonia. Drug susceptibility to M. pneumoniae 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 M. pneumoniae pneumonia, confirming that it was equally effective as minocycline.