Staphylococcus aureus adherence to nasal epithelial cells in a physiological in vitro model

Nasal carriage of Staphylococcus aureus represents a risk factor for subseq uent invasive infections and interpatient transmission of strains. No physi ological in vitro model of nasal epithelial cells is available to study bot h patient- and bacteria-related characteristics and their interaction, lead ing to adherence and colonization. Starting with tissues from human nasal p olyps, a confluent, squamous, nonkeratinized epithelium in collagen-coated 96-well microtiter plates was obtained after 14 d. This in vitro cell-layer was characterized histologically, ultrastructurally: and inmunohistochemic ally and showed features that were indistinguishable from those observed in the squamous nonkeratinized epithelium found in the posterior part of the vestibulum nasi, Adherence experiments were performed with four different H -3-thymidine-labeled Staphylococcus aureus strains. The effect of bacterial inoculum size, temperature of incubation, and incubation medium were studi ed. The adherence results were found to be reproducible, reliable and sensi tive, allowing detection of small quantitative differences in adherence bet ween the Staphylococcus aureus strains. There was no significant difference in adherence at 23 degrees C and 37 degrees C, nor between the incubation medium M199 and phosphate-buffered saline. Plastic adherence could be reduc ed and standardized with use of siliconized tips and a constant bacterial i noculum volume of 100 mu l/well. This physiological and reliable in vitro c ell-culture model, offers a unique opportunity to study Staphlococcus aureu s adherence to squamous, nonkeratinized nasal epithelial cells and both pat ient and bacterial characteristics involved in this interaction.