Quantitative Coagulase and Toxin Production by Staphylococcus in Relation to the Clinical Source of the Organisms *

Recent studies have reopened the problem of the relation of coagulase production to staphylococcal infection.3 Although the in vivo significance of this substance is controversial, there is very little question that the capacity of staphylococci to clot plasma in vitro serves as a useful index of pathogenicity. The test is usually carried out by inoculating rabbit or human plasma with a young, living culture. Coagulation of the plasma within 24 hours is regarded as positive. However, since the organisms continue to multiply during the incubation period, this procedure does not afford an accurate index of the quantity of coagulase formed by the strain. On the other hand, titration of suitable bacteria-free preparations under standard conditions might serve to indicate the quantitative limits of coagulase production by the staphylococci. Although it was at first asserted that living organisms were essential for the demonstration of coagulase, the studies of Walston"3 and of others' 7, 8 clearly proved that bacteria-free preparations might possess activity. No systematic studies, however, are extant to define the range of activity possessed by different strains. It therefore seemed desirable to determine the degree to which strains vary in their capacity to elaborate coagulase in vitro, and to note whether this property correlates with toxin production and with the clinical sources from which the strains have been derived.