Stability of two forms of Rappaport-Vassiliadis enrichment medium.

It has been shown previously (18) that the sensitivity of Rappaport-Vassiliadis medium (RV medium) prepared with tryptone Difco (RV-tryptone) in isolating salmonellae and its specificity in inhibiting competing organisms remains unchanged when the medium is held in a refrigerator for 6 to 7 months. In the present study it was found that the RV-tryptone medium held in the refrigerator for 13 to 15 months looses its specificity to a marked extent. Therefore it is prudent not to use RV-tryptone after storage of 7 months. On the other hand, it was observed that RV medium made with soya peptone (Oxoid L 44) (RV-soya) retains its sensitivity and specificity, and is therefore usable, when held in the refrigerator for 7 to 9 months and even when held at room temperature for 13 to 15 months.