The taxonomy and antimicrobial susceptibility of Haemophilus species in clinical specimens.

Organisms of the Haemophilus group isolated from nonrespiratory and respiratory sources were studied taxonomically. All biotypes of Haemophilus influenzae and Haemophilus parainfluenzae were encountered. However, nearly all H. influenzae from cerebrospinal fluids belonged to biotype I, while nearly all of those from conjunctivae belonged to biotype II. Only two of the 78 biotypable strains of H. influenzae produced beta-lactamase, but there was no other substantial difference in antimicrobial susceptibilities among biotypes of H. influenzae. Biotypes of H. parainfluenzae were less susceptible to penicillins and cephalosporins than those of H. influenzae.