Both Haemophilus influenzae and Abiotrophia defectiva, a species of
nutritionally-deficient Streptococcus, are unable to grow on blood
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 blood
Figure 2. Identification of bacteria by specialized microbiological
tests. (A) The CAMP test for identification of Group B
streptococcus (horizontal streak, GBS) demonstrates an arrowhead
shaped area of enhanced hemolysis when grown near S. aureus (vertical
streak, SA). (B) The reverse CAMP test for identification of Arcanobacterium
haemolyticum demonstrates an indentation in the linear area of
hemolysis by S. aureus (vertical streak, SA) when it grows adjacent to A.
haemolyticum (horizontal streak, AH). (C) The satellite test for
identification of Haemophilus influenzae demonstrates growth of the
organisms as small satellite colonies (arrowhead, H. flu) adjacent to S.
aureus (vertical streak, SA). Similar satellite colony formation around S.
aureus was seen for Abiotrophia defectiva. Similar results were seen on
both defibrinated and citrated hair sheep blood agar; results are shown
on citrated hair sheep blood agar plates.
doi:10.1371/journal.pone.0006141.g002