Clinical significance of serotype, biotype, and beta-lactamase production of respiratory isolates of Hemophilus influenzae.

The correlation between clinical significance and serotype, biotype, and beta-lactamase production of 101 respiratory isolates of Hemophilus influenza from nonbacteremic patients was determined. Six of 33 (18.2%) isolates from patients with definite or probable infection were serotypable; only two of 67 (3%) isolates from colonized patients were serotypable. Eight-seven and one-half per cent of the serotypable strains were biotypes I or IV; 78.8% of nonserotypable strains were biotypes II, III, or V. Biotype distribution among isolates from patients with definite or probable infection were similar to isolates from colonized patients. beta-lactamase production was not helpful in evaluating clinical significance. Nonserotypable H. influenzae is an important cause of nonbacteremic pneumonia in elderly men.