The effect of cellular pathology and keratinization of skin and nasal cells upon binding of Staphylococcus aureus were examined. Adherence with epithelial cells obtained from either the skin or nasal mucosa of patients with atopic dermatitis was greater than that observed with normal cells (p less than 0.001); the difference in adherence between psoriatic and normal cells was not statistically significant. Tested nasal cells were microscopically differentiated into 4 general types based on stage or layer of keratinization: spinous, low granular, high granular, and keratin. The degree of adherence was related to the progress of keratinization. Data indicated the existence of 2 types of receptors for S. aureus on nasal cells: One, present upon both granular and fully keratinized cells, is not blocked by teichoic acid and appears responsible for the higher bacterial counts on atopic cells; the second is found on keratinized cells only and is susceptible to teichoic acid.

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To determine whether competition among bacteria for specific attachment sites on host cells can explain bacterial interference, Staphylococcus aureus strain 502A was tested in turn against two different nasal coryneforms, a strain of Pseudomonas aeruginosa, and a virulent strain of S. aureus, all in the presence of nasal mucosal cells. Particularly examined was the influence of sequence in which bacteria were presented to the nasal cells in comparison with initial mixtures and individual suspensions. Results paralleled those observed in clinical prophylaxis: the bacterium first to adhere to the epithelial cells was able, under uniform conditions, to interfere with the colonization of subsequently added bacteria. Secondary adherence was not eliminated but substantially reduced, and was probably related to steric blockage by the initial colonizer and its particular ability to dissociate from the host cell.

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