Mucin in middle ear effusions inhibits attachment of Haemophilus influenzae to mucosal epithelial cells

Abstract

Although otitis media with effusion is often preceded by an infection of the tympanic cavity, when cultured, many effusions show no culturable bacteria. Based on the hypothesis that the effusion might play a protective role in the course of infection, the influence of this fluid on adhesion of H. influenzae (Hi) type-b strain 770235 and nontypeable H. influenaze (NTHi) strains to buccal epithelial cells was investigated. Effusions were classified as mucoid, seromucoid and serous. Mucoid secretions inhibited adhesion to a significantly greater extent (62%) than did seromucous (52%) and serous effusions (47%) ( P <0.001). The glycoprotein and high-molecular-weight fractions showed similar levels of inhibition. Sialic acid concentration, and, to a lesser extent, protein concentration, correlated with the level of inhibition. Desialylated effusions lost their ability to block bacterial attachment. Thus, middle ear effusion fluid exhibits an inhibitory effect that is due to mucins, which determine viscosity and represent the sialylated high-molecular-weight glycoprotein fraction of the effusion.