Difco™ Salmonella O, H and Vi Antisera are lyophilised, polyclonal rabbit antisera containing approximately 0.04% Thimerosal as a preservative. Difco™ Salmonella O Poly Antisera are polyvalent antisera. Each antiserum is specific for certain serogroup antigens. When properly rehydrated and used as recommended, each vial of Difco™ Salmonella O or Vi Antisera contains sufficient reagent for 60 tests.