Dynamics of salmonella isolation with modified Rappaport's medium (R10)

Van Schothorst, M.; Renaud, A.M.

Journal of Applied Bacteriology 54(2): 209-215


ISSN/ISBN: 0021-8847
PMID: 6853397
Document Number: 407
Enhanced growth of salmonellas in Rappaport's medium as modified by Vassiliadis et al. (1976) after pre-enrichment in buffered peptone water during the first 6 h was obtained by replacement of tryptone by soy peptone. The competing bacteria, i.e., those which grow on brilliant green agar and which may interfere with the isolation of salmonellas when Rappaport's medium (R10) incubated at 43.degree. C is used for enrichment, were inhibited or reduced in numbers when the normal amount of 5 g soy peptone/l was used. When the amount was increased to 10 g/l, growth occurred, mainly of Enterobacter and Klebsiella spp. The isolation of salmonellas was largely dependent on the number and the ratio of their competitors. Every measure taken to reduce the number of competitive bacteria increases the possibility of isolating salmonellas. This explains the effect of improved selectivity of Rappaport's medium when small inocula are used. Rapid onset of growth of salmonellas by employing soy peptone introduces the possibility of using incubation times shorter than 48 h.

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Dynamics of salmonella isolation with modified Rappaport's medium (R10)