Two Cases in which Tosufloxacin was Administered for Respiratory Infections that may have been Caused by Haemophilus influenzae less Susceptible to Quinolone

Abstract

In Japan, tosufloxacin has been used for the treatment of paediatric respiratory infectious diseases caused by respiratory pathogens, such as Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae, since 2010. However, H. influenzae, a major respiratory pathogen, that shows low susceptibility to quinolones has already emerged. In this study, we encountered two lower respiratory infection cases that were suspected to have low-susceptible H. influenzae as a causative pathogen. Although these isolates were judged as “susceptible” by the in-hospital routine susceptibility test, these cases did not respond to tosufloxacin treatment and had to be treated with β-lactams. These findings strongly suggest that when using quinolones, low-susceptible strains among “susceptible strains” should be taken into account.