A negative tube coagulase test result given by Staphylococcus epidermidis after a 24-hour incubation in coagulase plasma. A negative reaction is indicated by a lack of clotting in the tilted tube. (D. Sue Katz, Rogers State University, Claremore, OK)

Coagulase-negative staphylococci. Note the individual cells and lack of large clumps of cells.  Cells on the slide coagulase test slide were dried, heat fixed, and stained with methylene blue. Photograph is at 1,000X magnification.  (D. Sue Katz, Rogers State University, Claremore, OK)

Coagulase-positive staphylococci.  While some individual cells are observed, the majority of cells are gathered into a large clump, large enough to be visible to the naked eye.  Cells on the slide coagulase test slide were dried, heat fixed, and stained with methylene blue.  Photograph is at 1,000X magnification.  (D. Sue Katz, Rogers State University, Claremore, OK)

Slide coagulase test results. (Right) A positive slide coagulase test result for Staphylococcus aureus when mixed with coagulase plasma. A positive reaction is indicated by visible clumping of Staphylococcus aureus. (Left)  A negative slide coagulase test result for Staphylococcus epidermidis when mixed with coagulase plasma. A negative reaction is indicated by no visible clumping. (D. Sue Katz, Rogers State University, Claremore, OK)

Tube coagulase test results.  (Left) A negative tube coagulase test result for Staphylococcus epidermidis after a 24-hour incubation in coagulase plasma. A negative reaction is indicated by a lack clotting in the tilted tube. (Right) An uninoculated control is also shown. (D. Sue Katz, Rogers State University, Claremore, OK)

Tube coagulase test results.  (Left) A negative tube coagulase test result for Staphylococcus epidermidis after a 24-hour incubation in coagulase plasma. A negative reaction is indicated by a lack clotting in the tilted tube. (Right) An uninoculated control is also shown. (D. Sue Katz, Rogers State University, Claremore, OK)

Tube coagulase test results. (Right) A positive tube coagualse test result for Staphylococus aureus after a 24-hour incubation in coagulase plasma. A positive reaction is indicated by clotting in the tube.  (Left) A negative tube coagulase test result for Staphylococcus epidermidis after a 24-hour incubation in coagulase plasma. A negative reaction is indicated by a lack of clotting in the tube.  (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus aureus cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note the presence of large clumps of cells. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus aureus cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note the presence of large clumps of cells. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus aureus cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note the presence of large clumps of cells. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus aureus cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note the presence of large clumps of cells. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus epidermidis cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note that the cells are well dispersed and in large clumps. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus epidermidis cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note that the cells are well dispersed and in large clumps. (D. Sue Katz, Rogers State University, Claremore, OK)

Staphylococcus epidermidis cells observed under an oil immersion lens after the coagulase test slide was dried, fixed, and stained. Note that the cells are well dispersed and in large clumps. (D. Sue Katz, Rogers State University, Claremore, OK)

Close-up of a positive slide coagulase test result given by Staphylococcus aureus mixed with coagulase plasma. A positive reaction is indicated by visible clumping of Staphylococcus aureus. (D. Sue Katz, Rogers State University, Claremore, OK)

Close-up of a negative slide coagulase test result given by Staphylococcus epidermidis mixed with coagulase plasma. A negative reaction is indicated by no visible clumping. (D. Sue Katz, Rogers State University, Claremore, OK)

Tube coagulase test results. (top) A positive tube coagulase test of +3 designation is indicated by a well-formed clot in the test tube. (bottom) A negative tube coagulase test is indicated by a lack of clotting in the tube. (Diane Hartman, Baylor University, Waco, TX)

A postive tube coagulase test of +2 designation is indicated by a soft clot "stingray" form in the test tube when tilted.  (Diane Hartman, Baylor University, Waco, TX)

A negative tube coagulase test after a 24-hour incubation in coagulase plasma. A negative reaction is indicated by a lack clotting in the tilted tube. (Diane Hartman, Baylor University, Waco, TX)