A comparison of two modifications of Rappaport's enrichment medium (R25 and RV) for the isolation of salmonellas from sewage polluted natural water.

The development of Rappaport's enrichment medium and elevated temperature incubation as methods of salmonella isolation is traced. The recent recording of a merger of the two techniques by means of Rappaport--Vassiliadis medium is noted (RV medium). In Cardiff, we have found an earlier modification of Rappaport's enrichment (R25) by Vassiliadis to be efficient in salmonella recovery from environment samples. The current study compares the two media using sewage polluted natural water as test material. Under the conditions of experiment, R25 was more successful in salmonella isolation than RV, although the later medium inhibited competitive organisms better. R25 is a convenient enrichment broth for routine use. In combination with pre-enrichment it allows the use of a loop for subculture rather than a pipette. This increases safe manipulation. It also produces a high proportion of positive isolations at the 24 h subculture time in contrast to other enrichment broths. For these reasons it forms an integral part of salmonella isolation methodology in our laboratory.