Middle ear effusion IL-6 concentration in bacterial and non-bacterial acute otitis media

Background: The pathogenesis of acute otitis media is complex and multifactorial. It is characterized by inflammation of the middle ear with an infiltration of leukocytes, macrophages and mast cells. The resulting effusion contains a large amount of inflammatory mediators, among which are cytokines. Objectives: To test the role of IL-6 in the inflammatory process associated with acute otitis media. Methods: We analyzed 20 middle ear fluid (MEF) sample pairs, obtained by aspiration before initiating antibiotic therapy (day 1) and during treatment (days 4-5), for the presence of IL-6. IL-6 concentrations were assayed with an ELISA kit (detection limit 5 pg/ml) and were correlated with bacterial etiology and bacterial eradication from the middle ear. Results: IL-6 was detected in all middle ear effusions analyzed. We found decreased IL-6 concentrations in culture negative MEF compared to culture positive MEF on both days 1 and 4-5 (day 1, 1752.20 +/- 1001.31 pg/ml vs 1216.20 +/- 1015.44 pg/ml, p = 0.19; days 4-5, 1049.36 +/- 472.40 pg/ml vs 800.33 +/- 676.00 pg/ml, p = 0.23); however, differences did not achieve statistical significance. Overall, a marked and significant decrease in IL-6 concentration occurred following 72-96 h of antibiotic therapy (1618.15 +/- 1004.88 pg/ml vs 936.85 +/- 581.05 pg/ml, p = 0.04). While MEF IL-6 concentrations decreased in ears where bacteria persisted (1468.20 +/- 858.48 pg/ml vs 1044.80 +/- 514.16 pg/ml, p = 0.167) or were eradicated (2320.20 +/- 866.16 pg/ml vs 767.40 +/- 522.88 pg/ml, p = 0.029), a more prominent decline was demonstrated in the latter. Conclusions: These results strongly suggest the involvement of IL-6 in the ongoing inflammatory process in both bacterial and non-bacterial acute otitis media. Resolution of inflammation in the middle ear, especially where bacteria were eradicated, is reflected by low IL-6 levels.