Distribution of biotypes of Haemophilus influenzae and H parainfluenzae in patients with cystic fibrosis.

One hundred and eighty eight isolates of Haemophilus influenzae and 187 isolates of H parainfluenzae from patients with cystic fibrosis, patients with respiratory infections but without cystic fibrosis, and patients with neither cystic fibrosis nor respiratory infections were biotyped. Biotype I of H influenzae were found significantly more often in patients with cystic fibrosis compared with those with normal respiratory tracts. On the other hand, biotype II strains of H influenzae were found less often in the cystic fibrosis group. Half of the biotype V strains produced beta-lactamase.