Production of RNA-dependent haemolysin by Haemophilus pleuropneumoniae

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Abstract
Five strains of H. pleuropneumoniae, out of 8 strains tested produced extracellular hemolysin(s) when grown in liquid culture in the presence, but not in the absence, of RNA. The hemolysin produced by the neotype strain was unstable, heat labile and sensitive to degradation by pronase, trypsin and chymotrypsin trypan blue treated hemolysin preparations were less effective at causing erythrocyte lysis than were untreated preparations. Following growth in the absence of RNA, washed suspensions of the neotype strain produced extracellular hemolysin when incubated in the presence of RNA, glucose and casein acid hydrolysate; extracellular haemolysin could not be detected if the incubation mixture contained chloramphenicol. The hemolysin produced by washed bacterial suspensions was similar to that produced by growing cultures in that it was unstable, heat labile and sensitive to inactivation by the same complement of enzymes. Erythrocyte lysis induced by either hemolysin preparation was preceded by a prelytic phase, the duration of which was dependent upon hemolysin concentration and the initial temperature of the hemolysin-erythrocyte mixture. The haemolysin(s) produced by the neotype strain of H. pleuropneumoniae is distinct from, but closely related to streptolysin S and the hemolysin produced by Treponema hyodysenteriae.