HEMOLYSIN-INHIBITING SUBSTANCE IN STAPHYLOCOCCUS AUREUS STRAINS.

Cetin, E. T. (Istanbul University, Istanbul, Turkey). Hemolysin-inhibiting substance in Staphylococcus aureus strains. J. Bacteriol. 86:407-413. 1963.-Of 144 Staphylococcus aureus strains isolated from pathological specimens, 3.4% did not cause hemolysis on sheep blood agar; the remainder produced hemolytic and semihemolytic zones, most of which were surrounded by a dense red band. Most of the strains causing pronounced hemolysis and a large dense red band on sheep blood agar also produced a dense red band on human blood agar after incubation at 37 C for about 1 week. In the dense red band on human blood agar, circles of hemolysis were observed when petri dishes were kept at room temperature for approximately 1 more week. The dense red band inhibited delta hemolysis of some of the S. aureus strains growing nearby. Certain strains failing to produce the dense red band on human blood agar inhibited delta hemolysis of other strains grown near them. A hemolysis-inhibiting substance (HIS) was produced in broth and agar media, and could be extracted from agar cultures. HIS was stable for 1 hr at 56 C and for 15 min at 100 C. It lost 75% of its effect when heated for 30 min at 100 C and became ineffective when heated at the same temperature for 45 min. Conditioned hemolysis occurred when some saprophytic gram-positive bacteria grew near or within the dense red band. These organisms also produced conditioned hemolysis without the presence of a visible dense red band, when growing near the strains inhibiting delta hemolysis. When such strains were grown on human blood agar, a conditioned hemolysis also occurred after the border of the medium was flamed.