V-factor or nicotinamide adenine dinucleotide (NAD) is a coenzyme involved in redox reactions. Some bacteria cannot produce NAD
and need to get it from the substrate or grow as a satellite of a NAD-producing organism.
Satellitism can be demonstrated on an agar medium lacking the V-factor by
cross-inoculating the plate with a feeder strain (e.g. Staphylococcus or
Pseudomonas). The NAD-requiring strain will grow only in the vicinity of the
V-factor impregnated disks may be used instead of the feeder strain.
NAD is destroyed by autoclaving the medium.
The satellite phenomenon may be difficult to achieve in ordinary agar plates because
blood may contain various amounts of V-factor. For a NAD-free medium autoclaving is
required after adding the blood.
1. H. Raducanescu, V. Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. J. G.Holt et al., 1994.Begey’s manual of Determinative Bacteriology, 9-edition, Williams & Wilkins.
(c) Costin Stoica
|Actinobacillus pleuropneumoniae (pinpoint
colonies) dependent of V factor (NAD) - producing
Staphylococcus aureus (yellow line)