Biochemical Properties and Antimicrobial Susceptibility of Recent Clinical Isolates of <i>Haemophilus</i> Species

Classification of the genus Haemophilus remained confused until 1976 when Kilian (8) proposed an excellent classification based on his detailed taxonomic study of this genus. This stimulated us to reclassify our recent clinical isolates of Haemophilus according to the biotypes of his schema. They were further serotyped and their susceptibility to nine antimicrobial agents was determined. The 50 strains of Haemophilus species had been recently isolated from clinical specimens submitted to our laboratory for bacteriological examination. The majority of the isolates were from the respiratory tract (sputa, pharyngeal swabs, or bronchial brushings), with a small number coming from other sources. The porphyrin test to determine the ability to synthesize porphyrins from 0­ aminolaevulinic acid (ALA) was carried out as described by Kilian (7). The V factor requirement was tested by X,V discs (Eiken) on X,V disc medium (Eiken). Urease activity was tested in Stuart's urea broth. Decarboxylation of ornithine and lysine and dihydrolation of arginine were examined by M011er's method (12). For the tryptophanase (indoI production) test, cultures were inoculated into LIM medium (Nissui) to which, immediately after autoclaving, defibrinated horse blood had been added to a final concentration of 5%, and incubated for 48 hr at 37 C; the formation of indol was determined with Ehrlich's reagent. Lead acetate paper strips, placed in the upper part of the chocolate agar slant, were used to detect the production of H 2S. Hemolytic activity was determined on NHM medium (Kyokuto) containing defibrinated horse blood at a concentration of 5%. Pro­ duction of acid from glucose, sucrose, lactose, xylose, and mannitol, and gas for­ mation from glucose, were tested in phenol red broth (Difco) as described by Kilian (8). Catalase was detected by emulsifying a fresh colony from a chocolate agar plate in a drop of 5% H 20 2 on a slide, and examining it for the formation of bubbles of oxygen. The hemagglutination test was performed in test tubes (8 mm X 80 mm) by mixing 0.5 ml of a 1% (v/v) suspension of human group 0 erythro­ cytes in saline (0.85%, NaCI), incubating the tubes at room temperature for 2 hr and reading the results after storage at 4 C for 18 hr. Capsular antigens were