Resident aerobic microbiota of the adult human nasal cavity

Recent evidence strongly suggests that the microbiota of the nasal cavity p lays a crucial role in determining the reaction patterns of the mucosal and systemic immune system. However, little is known about the normal microbio ta of the nasal cavity. The purpose of this study was to determine the micr obiota in different parts of the nasal cavity and to develop and evaluate m ethods for this purpose. Samples were collected from 10 healthy adults by n asal washes and by swabbing of the mucosa through a sterile introduction de vice. Both methods gave results that were quantitatively and qualitatively reproducible, and revealed significant differences in the density of the na sal microbiota between individuals. The study revealed absence of Gram-nega tive bacteria that are regular members of the commensal microbiota of the p harynx. Likewise, viridans type streptococci were sparsely represented. The nasal microbiota was dominated by species of the genera Corynebacterium, A ureobacterium, Rhodococcus, and Staphylococcus, including S. epidermis, S. capitis, S. hominis, S. haemolyticus, S. lugdunensis and S, warneri. These studies show that the microbiota of the nasal cavity of adults is strikingl y different from that of the pharynx, and that the nasal cavity is a primar y habitat for several species of diphtheroids recognized as opportunistic p athogens. Under special circumstances, single species, including IgA1 prote ase-producing bacteria, may become predominant in a restricted area of the nasal mucosa.