it has been found that minimum concentration of stabilizers in the compositions of the present invention necessary for obtaining a stabilizing effect is about 0 005 weight volume although there is no critical maximum concentration of stabilizer in the compositions of the present invention amounts greater than 1 0 weight volume concentration are acceptable but unnecessary and costly it is preferred to employ a stabilizer in the composition of the present invention of approximately 0 1 weight volume the stabilizers of the present invention are generally present in the compositions of the present invention in an ionic form it is preferred to add salts of gentamicin amikacin or tobramycin such as sulfates phosphates halides or nitrates to the peroxidase or peroxidase conjugates in addition to peroxidase and or peroxidase conjugates and stabilizers other constituents may be added to the compositions of the present invention in particular the compositions of the present invention may include but not limited to serum proteins such as fetal calf serum rabbit serum pig serum and the like and buffers such as tris u00b7 hcl buffer phosphate buffered saline and the like although the stable peroxidase compositions are preferable aqueous compositions the peroxidase compositions may be marketed as a lyophilized product a 1 1 mixture of commercially available normal rabbit serum and normal pig serum was pooled the serum was filtered to remove any precipitates and the filtrate was diluted with an equal volume of 0 1 m tris buffer ph 8 6 to provide a final concentration of 50 serum.