Tympanostomy Tube In Vitro Biofilm Potential of Common Otopathogens

Abstract

Objective. Post-tympanostomy tube otorrhea has been linked to microbial biofilms. The purpose of this study was to compare the tympanostomy tube-biofilm–forming propensity of common otopathogens Pseudomonas aeruginosa, Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pneumoniae. Study Design. Controlled, in vitro. Setting. Academic research laboratory. Subjects and Methods. Fluoroplastic coupons (1656 total, 46 per treatment per incubation period) were exposed to plasma and cultured with 3 strains each of the bacterial species for 2, 4, or 7 days. Half of the coupons were treated with antibiotics to kill planktonic bacteria. Total and biofilm colony counts and electron microscopy were performed. Results. S aureus formed biofilm after 2 days, not different from 4- or 7-day biofilms ( P > .05), and was most tolerant to antibiotic treatment. P aeruginosa also formed biofilms at 2 days, reached a plateau at 4 days ( P > .05), and decreased at 7 days ( P < .01). H influenzae formed biofilm only after 4 days ( P ≤ .04). S pneumoniae did not form biofilm without catalase supplementation. With catalase, 1 S pneumoniae strain showed a delay in biofilm formation similar to H influenzae ( P < .0001), while the other 2 strains formed biofilms after 2 days. Conclusions. Tympanostomy tube biofilm formation occurs with common middle ear pathogens but most readily with S aureus and P aeruginosa. Further investigation is needed to determine if these findings may, in part, explain the occasionally refractory nature of post-tympanostomy tube otorrhea associated with S aureus and P aeruginosa.