Radiometric detection of Haemophilus in simulated blood cultures

The radiometric detection of various Haemophilus species was studied in simulated blood cultures and in blood culture media without added blood, but supplemented with nicotinamide-adenine dinucleotide (NAD) or hemin, or both. Haemophilus aphrophilus was the only species studied that was radiometrically detectable without added blood or NAD. All other species studied (Haemophilus influenzae, Haemophilus parainfluenzae, Haemophilus haemolyticus, and Haemophilus parahaemolyticus) required either added NAD, whole blood, or washed blood cells for growth and radiometric detection. The results of this study and extensive experience with clinical specimens show that the radiometric system is an effective means of rapidly detecting Haemophilus in blood cultures, but it is essential that it be used in conjunction with a subculture three to five days after inoculation.