Planktonic Growth ofPseudomonas aeruginosaaround a Dual-Species Biofilm Supports the Growth ofFusobacterium nucleatumwithin That Biofilm

Abstract

Purpose.The goal of this study was to understand the potential interaction betweenPseudomonas aeruginosaandFusobacterium nucleatumwithin the middle ear.Methods.We examined the microbiota of ear fluid and tympanostomy tubes (TTs) obtained from patients with posttympanostomy tube otorrhea. We also examined biofilms formed byP. aeruginosaandF. nucleatum, singly or together, under aerobic or anaerobic conditions.Results.While the facultative anaerobeP. aeruginosadominated the bacterial population within the ear fluid, strict anaerobes, includingF. nucleatum,dominated bacterial populations within the TTs.F. nucleatumwas able to grow under aerobic conditions only in the presence ofP. aeruginosa, whose growth reduced the level of dissolved oxygen within the broth to nearly anoxic condition within 4 h after inoculation. The presence ofP. aeruginosaallowedF. nucleatumto maintain its growth for 72 h within the dual-species biofilm but not within the planktonic growth. Visualization of the biofilms revealed coaggregation ofP. aeruginosaandF. nucleatum.Conclusion.Extrapolation of these results suggests that, within the middle ear fluid, the growth ofP. aeruginosaproduces the anaerobic conditions required for the growth ofF. nucleatum, both within effusion and within biofilms.