Adherence of Haemophilus influenzae to Human Epithelial Cells

Abstract

Haemophilus influenzae organisms, both type b and non-typable strains, were tested for their adherence to human buccal epithelial cells. Adherence was determined by visual examination of gram-stained specimens of epithelial cells following incubation with H. influenzae. Among 36 isolates tested, 2 organisms adhered well to buccal cells; a type b nasopharyngeal isolate showed a mean of 19.94 bacteria per cell and a non-typable throat isolate showed a mean of 37.72 bacteria per cell. These isolates readily hemagglutinated human red blood cells. None of the other 12 type b blood or spinal fluid isolates tested adhered well (range 0.04–1.34 bacteria per cell) nor hemagglutinated red cells. There was no difference in the adherence of H. influenzae to buccal mucosal cells from 6 donors, and no difference between epithelial cells obtained from the buccal or nasal mucosa. Although both type b and non-typable H. influenzae strains appear capable of adhering to human epithelial cells, many strains do not. The role of adherence factors in the maintenance of mucosal colonization with these poorly-adherent strains remains unknown.