Biotypes of capsulated and non-capsulated Haemophilus influenzae. Correlation between biotypes and beta-lactamase...

396 Haemophilus influenzae strains were biotyped according to Kilian. 393 of the strains were assigned to biotypes I to V, while 3 strains remained unclassified. Eighty-nine per cent of the capsulated strains produced both urease and ornithine decarboxylase, biotypes I or IV, while 95 per cent of the non-capsulated strains produced only one of the enzymes, biotypes II, III, or V. Of consecutive strains from the upper respiratory tract, the incidence of beta-lactamase-positive strains was higher among capsulated than among non-capsulated strains (p less than 0.025). None of 133 non-capsulated beta-lactamase-positive strains produced both urease and ornithine decarboxylase, in contrast to 15 out of 147 non-capsulated beta-lactamase-negative strains (p less than 0.001). The type e strains were all of biotype IV and 3 of 7 consecutive strains were beta-lactamase-positive.