Tosufloxacin for Eradicating Biofilm-Forming Nontypeable Haemophilus influenzae Isolated from Intractable Acute Otitis Media

Nontypeable Haemophilus influenzae (NTHi)-caused acute otitis media persists even after antimicrobial treatment, presumably as a result of biofilm formation. It is urgent to establish an alternative antimicrobial treatment against acute otitis media that effectively deals with NTHi biofilm. An otopathogenic clinical strain of NTHi IH-202 isolated from the middle ear fluid of intractable pediatric cases of acute otitis media was used in the study. Antimicrobial susceptibility and biofilm assay using antimicrobial agent tosufloxacin were performed. Exposure to tosufloxacin at 0.96 µg/mL for 20 minutes reduced the amount of NTHi biofilm formation and killed viable NTHi in biofilm as compared with the control. A clinically attainable concentration of tosufloxacin could destroy NTHi biofilm and showed bactericidal activity against NTHi in biofilm in shorter exposure periods. The current findings suggest an alternative antimicrobial treatment strategy against intractable cases of acute otitis media caused by NTHi biofilms. Tosufloxacin will be an effective alternative for the treatment of intractable acute otitis media caused by NTHi biofilm. In addition, our in vitro bacteria-epithelial cell co-culture model is a relatively simple and static method for studying NTHi biofilms.