This image depicts the results of a reverse CAMP test which involved the growth of bacterial cultures on a medium of blood agar, for a 48hr period, in a CO2-rich environment. The CAMP test involves a bacterium that produces a ß-lysin (beta-lysin), which partially lyses, or destroys the red blood cells (RBCs) in the medium, which in this case is Staphylococcus aureus, i.e. the central vertical streak. The plate is then inoculated with test subject bacteria, which in this case was Arcanobacterium haemolyticum, formerly Corynebacterium haemolyticum (upper horizontal streak), and Arcanobacterium pyogenes, formerly Corynebacterium pyogenes (lower horizontal streak). Note that these streaks do not touch the central S. aureus streak.
As in its 24hr counterpart depicted in PHIL 14643, you’ll see that, as expected, the S. aureus produced an aura representing a hemolytic reaction in the blood agar medium. The A. haemolyticum inhibits the S. aureus hemolysis by excreting the protein phospholipase D, which is responsible for the inhibition of the hemolytic reaction (arrow heads). A. haemolyticum is the only Arcanobacterium that is reverse CAMP positive. The A. pyogenes produced a negative reverse CAMP test at the point where its streak intersected the S. aureus streak. Note that the resultant inhibitory effect, though not as prominent as that seen in the 24hr incubation image (PHIL 14643), is still apparent.