Determination of the hemin requirement of Haemophilus ducreyi: evaluation of the porphyrin test and media used in the satellite growth test.

Gonococcal (GC) agar supplemented with glucose and glutamine was found to be superior to Eugonagar and Trypticase soy agar in demonstrating the hemin requirement of 23 strains of Haemophilus ducreyi by the satellite growth test. The porphyrin test confirmed the requirement for exogenous hematin. With the agar dilution technique, using supplemented GC agar, the hemin concentration required to initiate growth was 10 microgram/ml, and the optimal hemin concentration to produce growth equivalent to that on chocolate agar was between 200 and 500 microgram/ml. On GC agar with added glucose and glutamine, the lowest hemin concentration impregnated in paper disks able to initiate satellite growth was 50 microgram/ml. The hemin requirements of these H. ducreyi were much higher than that reported for other Haemophilus species.