Study of nasopharyngeal bacterial flora. Variations in nasopharyngeal bacterial flora in schoolchildren and adults when administered antimicrobial agents.

Changes in nasopharyngeal bacterial flora in adults with acute upper respiratory tract infection on administration of antimicrobial agents were investigated, and how these changes contrasted with those in children. Many patients with acute sinusitis due to allergies, and patients with malignancy and diabetes mellitus were included in the investigation. The detection rates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, the major bacteria of acute otitis media (AOM), were 22%, 10%, and 7% respectively, which were significantly lower than those for children. Gram stain examination of nasopharyngeal swab samples showed a significant relation between leukocyte infiltration and the detection amount of S. pneumoniae (P = 0.0086). A significant relation (P = 0.0134) was also observed when H. influenzae was simultaneously detected. No significant change in the three major AOM bacteria present in nasopharyngeal bacterial flora after administration of antimicrobial agents was observed. However, all S. pneumoniae and H. influenzae detected after antimicrobial agent administration had the beta-lactam-resistance gene. It was observed that a significant improvement in leukocyte infiltration occurred 6 to 10 days after antimicrobial agent administration. In contrast, a significant improvement in children was observed at 2 to 5 days. In the adult subjects, this improvement was probably due to spontaneous remission rather than the effect of the antimicrobial agents. Although investigation of the long-term administration of antimicrobial agents was also conducted, its benefits for the patients were not elucidated.