Isolation of Haemophilus influenzae and Haemophilus parainfluenzae from genital-tract specimens with a selective culture medium

A series of 2027 genital tract specimens was cultured for Haemophilus species on non-selective chocolate agar and on a selective medium (Choc-VBCA). The latter gave a significantly higher isolation rate. H. influenzae was isolated from 27 specimens and H. parainfluenzae from 81 specimens by use of the selective medium. The biotype distribution of both species was compared with that of an equal number of isolates from respiratory-tract secretions. H. influenzae biotypes II and IV were found to predominate in genital strains and biotypes II and III in respiratory strains. With H. parainfluenzae, biotype II was most frequent in both sites. Two new biotypes of H. parainfluenzae (VI and VII) are described. The significance of the use of selective media and of biotype distribution are discussed.