Stable suspension for Vi-agglutination tests.

Two methods of preparing a stable suspension for Vi-agglutination tests are discussed. Both maintain Vi-agglutinability and O-inagglutinability after storage at 37 degrees C for 6 months, and the second also maintains the Vi-capsule-staining property. The first method involves the addition of 0.5% CaCl(2) to a heavy saline Vi-suspension, while in the second a similar suspension is treated with an 0.2% solution of chrome alum.