Tympanostomy tube in vitro biofilm potential of common otopathogens.

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.