27.2: Introduction

ELISA: See handout for all instructions

StaphTEX-Agglutination Reaction

Rapid tests are often used in a doctor’s office or clinic to identify bacteria. A very common one is a latex agglutination test for the causative agent of Strep Throat. A similar test, StaphTEX, can be done for Staphylococcus aureus a potentially serious pathogen. StaphTEX is also a latex agglutination test which looks for antigen (Ag)—the bacteria itself—in a patient sample. The test utilizes microscopic latex beads in a solution (blue in this case). Each latex bead is covered in antibodies (Ab) to the pathogen, and often other proteins. The StaphTEX beads are coated with both IgG Ab to S. aureus and the protein Fibrinogen. S. aureus produces Protein A which will attach to the IgG, and often also coagulase which affects fibrinogen. The latex beads have two ways then, of being affected by the S. aureus.

If S. aureus is present in the patient isolate an agglutination reaction occurs with the latex beads and will be visible as the precipitation of blue clumps. A negative test will not have clumping.