Effect of Haemophilus influenzae exposure on Staphylococcus aureus tympanostomy tube attachment and biofilm formation.

Abstract

Tympanostomy tube (TT) biofilm formation may lead to sequelae. To determine whether the acute pathogen Haemophilus influenzae promotes TT attachment and biofilm formation by the chronic pathogen Staphylococcus aureus. Controlled, in vitro microbiological study at an academic research laboratory using TTs treated with 0 (untreated), 10, or 3000 µg/mL ciprofloxacin or ethylene oxide and TTs with and without prior H influenzae exposure. Fluoroplastic TTs (18 per treatment) were cultured with H influenzae. The TTs were gas-sterilized or exposed to 0, 10, or 3000 µg/mL ciprofloxacin. One-third of the TTs from each treatment group underwent H influenzae counts or scanning electron microscopy (SEM). Another one-third were used for an S aureus attachment assay. The remainder, as well as TTs not exposed to H influenzae, were cultured with S aureus and then treated with oxacillin to kill planktonic S aureus. S aureus counts and SEM were performed. Attachment and biofilm formation of S aureus on TTs assessed by quantitative bacterial counts and SEM. Mean (SD) H influenzae counts were lower on TTs treated with 3 mg/mL than with 10 µg/mL ciprofloxacin (2.06 × 103 [1.00 × 103] vs 4.21 × 105 [1.67 × 105]; P < .001). Mean (SD) S aureus attachment was higher on TTs with untreated preexisting H influenzae (8.88 × 105 [3.20 × 105]; P < .001) and lower on TTs with prior exposure to H influenzae treated with 10 (3.43 × 104 [2.10 × 104]; P = .006) or 3000 µg/mL ciprofloxacin (6.41 × 102 [3.59 × 102]; P < .001). S aureus biofilm formation was similar across groups, except TTs with prior exposure to H influenzae treated with ciprofloxacin 3 mg/mL, which had significantly less (9.30 × 101 [3.51 × 102]; P < .001). Exposure to live H influenzae may promote S aureus attachment on TTs. Treatment of H influenzae on TTs with ciprofloxacin, 3 mg/mL, as found in ototopical therapy, may reduce subsequent S aureus attachment and biofilm formation.