Evaluation of some methods for the laboratory identification of Haemophilus influenzae.
Five tests--satellitism, synthesis of porphyrins, acid production from sucrose, beta-galactosidase activity (ONPG), and indole production--to differentiate between strains of Haemophilus influenzae and strains of V-dependent Haemophilus species were evaluated. Six per cent of strains of H influenzae were misidentified as H parainfluenzae by a test for satellitism using filter paper discs impregnated with X factor, V factor, or both, applied to Columbia Agar. None of seven nutrient agars tested grew Haemophilus species, and determined accurately the X factor requirement. Synthesis of porphyrins from delta-aminolaevulinic acid provided a reliable means of demonstrating that X factor was required. A test for the production of acid from sucrose discriminated successfully between strains of V-dependent Haemophilus species (positive) and H influenzae (negative). Most isolates were identified correctly by the ONPG test, but occasional V-dependent strains were negative and could be misidentified as H influenzae. The discriminative value of the indole test was unsatisfactorily low. The results of the tests are discussed in relation to the identification of H influenzae in the diagnostic laboratory.
D003470:Culture Media; D005069:Evaluation Studies as Topic; D006192:Haemophilus Infections / Q000175:diagnosis; D006193:Haemophilus influenzae / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000096:biosynthesis; D011166:Porphyrins / Q000096:biosynthesis; D013395:Sucrose / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D003470:Culture Media; D007211:Indoles; D011166:Porphyrins; D013395:Sucrose; D001616:beta-Galactosidase