agar because they lack some factor required for survival on blood
media. In the case of H. influenzae the missing factor is
nicotinamide adenine dinucleotide (NAD), and for A. defectiva a
source of pyridoxal must be provided [14–17]. S. aureus secretes
both NAD and pyrdixoxal and therefore permits the growth of
both organisms on blood agar as satellite colonies. In the satellite
test, both H. influenzae and A. defectiva grew on hair sheep bloodagar as small satellite colonies adjacent to S. aureus but nowhere
else on the plate (Figure 2C).