Studies on the virulence of staphylococci. l. Relationship between the virulence and deoxyribonuclease and coagulase activities

Studies were carried out on five staphylococcal strains with special reference to coagulase production, deoxyribonuclease activity and virulence. The experimental animals used were mice of the dd strain. They were inoculated intraperitoneally throughout the experiments.Results obtained are as follows.1) The lethal effect of the broth culture differed from strain to strain, irrespective of coagulase production and nuclease activity. Some of the nuclease-positive strains were of lower virulence, while some of the coagulase-negative strains showed a high virulence.2) The same result was obtained in any cases, as determined by lethality for mice within 14 days after inoculation or by the time of death after inoculation. It was not necessary to observe the animals beyond 72 hours for this purpose.3) Some strains produced a toxic substance in the culture filtrate. The substance was eluted from an ECTEOLA- or DEAE-cellulose column with 0.001M∼0.02M phosphate buffer (pH 7.1). In some strains which were coagulase-negative and nuclease-positive, the culture filtrate showed an inhibiting effect against the virulence of the other strains.4) Cell infiltration, induration and abscess formation were seen at the site of injection in some cases injected with coagulase-positive, nuclease-positive strains. Any coagulase-negative, nuclease-positive strains did not induced such effect, even though they showed a relatively high virulence.5) The inoculated organisms were distributed mainly in liver, spleen, and kidney, irrespective of virulence.