Pseudomonas Biofilm Formation after Haemophilus Infection

Objectives. Tympanostomy tube (TT) biofilm formation may lead to refractory otorrhea and occlusion. Biofilms are commonly composed of multiple microbial species. One species may promote or inhibit biofilm formation by other species. The aim of this study was to determine if Haemophilus influenzae (HI) promotes the development of Pseudomonas aeruginosa (PA) biofilm on TTs.

Study Design. Controlled, in vitro.

Setting. Academic research laboratory.

Subjects and Methods. Fluoroplastic TTs (20 per group) were exposed to plasma, allowed to dry, and cultured with HI for 7 days. TTs were either gas sterilized or treated for 24 hours with 10 or 3000 µg/mL ciprofloxacin. Half of the TTs from each treatment group underwent bacterial counts or scanning electron microscopy. The remainder, as well as TTs not exposed to HI, were cultured with PA for 4 days and treated with gentamicin to kill planktonic PA. Biofilm formation was quantified with bacterial counts.

Results. TTs treated with ciprofloxacin 3000 µg/mL had lower HI counts than TTs treated with 10 µg/mL (P = .0001), but viable HI persisted. PA biofilm formation on TTs with prior HI biofilm and treated with ciprofloxacin 10 µg/mL or gas sterilization was not different than TTs without HI. Less PA biofilm formed on TTs with HI treated with 3 mg/mL ciprofloxacin (P = .002).

Conclusions. HI biofilm does not promote PA biofilm formation on TTs. Use of high-dose ototopical therapy to clear HI may reduce subsequent PA biofilm formation.