The rapid recognition of Staphylococcus aureus: desoxyribonuclease and coagulase tests in correlation with sensitivities and other properties.

WHEN. in a routine laboratory, large numbers of cultures have to be made, many of them are incubated late in the afternoon and examined the next morning. When colonies of Staphylococcus aureus grow after a short incubation period few produce pigment, and it is impossible to say definitely if they are, in fact, Staph. aureus or Staph. albus. It is usual to test these organisms for coagulase but it may be necessary to come to a preliminary conclusion before the coagulase test can be done. They can be tested for desoxyribonuclease, and this may be quicker and more convenient than the coagulase test; but a simpler aid to a preliminary opinion is a selective indicator medium, and such a medium has been described by Davis and Davis (1965). It was decided to try this, and at the same time compare the coagulase test and the test for desoxyribonuclease on each Staph. aureus isolated. The opportunity was also taken to test the organisms for their sensitivity to antibiotics and their resistance to mercury salts, to phage type them, and to enquire into the source of infection in each case.