[A new oxygen-labile hemolysin in Klebsiella pneumoniae].

The hemolytic activity of sixty K. pneumoniae strains was investigated in tryptic soy agar with rabbit, dog, sheep, human, chicken and mouse blood. All of them were lytic only for rabbit red cells. In liquid medium it was necessary a 2 mercaptoethanol treatment to detect a good degree of hemolysis. Cultures in tryptic soy broth gave 100% hemolysis in assays with rabbit erythrocytes and only when hemolysin was concentrated by purification was it active on dog and sheep but in a lesser degree (7.5% hemolysis). Supernatants of cultures were precipitated at different saline concentrations; the fraction obtained with 30-50% (NH4)2SO4 had hemolytic activity after dialysis and 2 mercaptoethanol treatment. Then this fraction was eluted in a Sephadex G-100 column, but electrophoresis in polyacrylamide gel showed that the hemolytic molecules obtained by gel filtration were contaminated with protein structures which had different electrophoretic migration. Ion-exchange chromatography showed best purification index and the recovery of activity was over 100%, it was possible to explain this good recovery once an inhibitor was detected. Two rabbit red cell lysins were purified, both shared several properties: SH-activation, pH optimum, thermolability, selectivity for rabbit red cells, mechanism of action, inhibition by cholesterol and divalent cations.