Rapid porphyrin and cytochrome test


HardyDisk™ ALA (delta-aminolevulinic) Differentiation Disks rapidly detect the presence of porphyrin and cytochrome compounds and are used to differentiate Haemophilus species.


Traditionally Haemophilus species have been differentiated by their varying requirements for hemin (X-Factor), NAD (nicotinamide adenine dinucleotide, V-Factor), and a combination of hemin and NAD (XV-Factor). However, erroneous results have been demonstrated when using growth factor requirement tests. These misidentifications are largely attributed to the carryover of X-Factor in the inoculum as well as the presence of trace amounts of X-Factor in the medium. The use of HardyDisk™ ALA Differentiation Disk is used as an alternative method to X-Factor requirement testing. The ALA procedure is a more rapid test method as well as a more accurate method for determining hemin requirements by eliminating the erroneous results associated with X-Factor requirement tests. HardyDisk™ ALA Differentiation Disk assesses the ability of a Haemophilus strain to synthesize hemin from the ALA substrate. The test detects the presence of porphyrin compounds, which are intermediates in the hemin biosynthetic pathway. Porphyrins are detected by the emission of a red-orange fluorescence under UV light (366nm) and indicate that the organism is capable of synthesizing hemin and is not dependent on hemin (X-Factor) for growth. Conversely, hemin requiring strains lack the enzymes to synthesize hemin and do not produce intermediate porphyrin compounds.


Each HardyDisk™ ALA Differentiation Disk is prepared by impregnating carefully controlled concentrations of delta-aminolevulinic acid onto a high quality 6mm diameter filter paper disk.

Cat. no. HDZ7081
Size: 50 disks


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