Bacterial adherence to pharyngeal cells: in vitro studies with alpha-haemolytic streptococci and Haemophilus influenzae.

We examined the adherence to pharyngeal cells of alpha-haemolytic Streptococci (AHS) and Haemophilus influenzae, representing normal flora and otitis media (OM) pathogens, respectively. The bacteria were incubated with epithelial cells brushed from the tonsils, adenoid or tubal orifice of children and adults. Adherence varied among the clinical isolates of AHS and H. influenzae. AHS adhered better to epithelial cells from a child compared with those sampled from an adult. The bacteria adhered better to cells from the tubal orifice compared with those sampled from the adenoid. The selective attachment of AHS to certain cells but not to others could not be correlated to apoptotic/necrotic cells versus viable cells. Incubation of epithelial cells with an isolate of AHS with good inhibitory activity against OM pathogens showed almost no adherence of bacteria to the epithelial cells after 12 and 24 h of incubation. If, however, an isolate of AHS with weak inhibitory activity was incubated with the cells, the bacteria that were attached to the epithelial cells from the beginning showed overgrowth in the broth and increasing attachment to the cells after 12 and 24 h. Thus the inhibitory activity of AHS could also affect the adherence of potential pathogens to the mucosal surfaces. The adherence pattern may at least partially explain the difference in susceptibility to OM between children and adults.