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 24hr 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.
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. Note that the A. pyogenes produced a negative reverse CAMP test at the point where its streak intersected the S. aureus streak. See PHIL 14644, for an image depicting this culture plate after a 48hr time period; where; the additional incubational time has somewhat clouded the results; though the inhibition is still evident.