Biotypes of Haemophilus encountered in clinical laboratories

Abstract

The biochemical characteristics of 464 strains of Haemophilus influenzae and 83 strains of Haemophilus parainfluenzae isolated over an 18-month period are described. Of 22 characteristics obtained, only 6 were necessary to biochemically identify and biotype the isolates. The key substrates or tests were urease, ornithine, indole, o-nitrophenyl-beta-D-galactopyranoside, sucrose, and xylose. Five biotypes of H. influenzae and four of H. parainfluenzae were commonly recognized. Some strains were encountered which could not be accommodated in the recognized taxa but which constituted separate biotypes of the two species, H. influenzae biotype I was recovered principally from blood, cerebrospinal fluid, and upper respiratory secretion, and biotypes II and III were recovered from eye and sputum cultures. Biotype I was recovered primarily from children less than 1 year of age, whereas biotypes II and III were from persons 1 to 5 years old and from those over 20 years of age. Multiple isolates recovered from the same patient were almost always of the same biotype. Strains of H. parainfluenzae were isolated primarily from sputum, with others being isolated from body sources such as dental abscesses, gastric aspirates, and peritoneal fluid. An inverse relationship was noticed between hemolysis and mannose fermentation among H. parainfluenzae biotype III strains, whereas the relationship was absent among the other biotypes.