X and V Factor Test- Principle, Procedure, Results, Limitations


The objective of X and V factor test is to differentiate among Haemophilus species based on their requirements for X and V factors for growth. Haemophilus species are gram-negative bacteria that can cause various infections in humans, such as respiratory tract infections, meningitis, otitis media, conjunctivitis, and sexually transmitted diseases. Some Haemophilus species require certain growth factors that are not present in the usual culture media, such as blood agar or chocolate agar. These growth factors are X factor (hemin) and V factor (nicotinamide-adenine-dinucleotide or NAD). The presence or absence of these factors can help identify the species of Haemophilus and guide the appropriate treatment. For example, Haemophilus influenzae requires both X and V factors, Haemophilus parainfluenzae requires only V factor, and Haemophilus ducreyi requires only X factor. Therefore, the X and V factor test is a simple and useful method to distinguish among these clinically important bacteria.