Inhibition of a staphylococcal hemolysin by a soluble substance produced by a nonhemolytic micrococcus species.

A colony of a yellow pigment forming, nonhemolytic Micrococcus species (tentatively identified as Micrococcus luteus) was found on a human blood agar plate close to a hemolytic staphylococcal colony. It was also noted that the zone of hemolysis of this Staphylococcus (the term Micrococcus is not used here for this organism to avoid confusion with the other) was slightly but definitely indented on the side near the colony of the micrococcus. This suggested that the hemolysis was inhibited by some soluble substances produced by the nonhemolytic micrococcus. Observation of hemolysis on blood agar plate. Since both organisms started growing at the same time on this plate, it was understandable that the inhibition of hemolysis was not marked because once hemolysis occurs, the effect of antihemolysis will never appear. It was decided to see the effect of this antihemolytic activity by allowing the micrococcus to grow for 24 hours in advance on blood agar plate and then streaking the hemolytic staphylococcus around it. Figure 1 shows one such culture. The horizontal line is the micrococcus grown for 24 hours at 37 C in advance, and the staphylococcus was then streaked vertically on both sides of the former. The plate was incubated for another 24 hours. It can be noted that the portions of both staphylococcal colonies near the line of the micrococcus do not exhibit any hemolysis although the growth of the organism itself was never inhibited. The staphylococcus