Fermentation of salts of organic acids as an aid to the differentiation of bacterial types / by H.C. Brown, J.T. Duncan and T.A. Henry.

  • Brown, H. C. (Henry Coddington)
Date:
[1924.]
Catalogue details

Licence: Public Domain Mark

Credit: Fermentation of salts of organic acids as an aid to the differentiation of bacterial types / by H.C. Brown, J.T. Duncan and T.A. Henry. Source: Wellcome Collection.

    17/32 page 15
    acetate yields a small precipitate of lead carbonate. These two precipitates can be easily differentiated by adding a little acetic acid, which dissolves the lead carbonate but not the lead mucate. The technique of the precipitation test must therefore be modified in the case of this salt by the addition of glacial acetic acid to the lead acetate solution: the proportions employed by us are glacial acetic acid 0-4 c.c. and saturated solution of lead acetate 0-6 c.c. to 5-0 c.c. of the mucate culture. If the mucate is unaltered, a dense turbidity settling down to a small precipitate results, but if decomposition of the salt has occurred, no precipitate follows the addition of the acid lead acetate solution. The following types constantly decomposed the 1 per cent, sodium mucate medium, B. paratyphosus B, Mutton, Newport, Stanley, Binns, Heading and Gartner. It was not decomposed by B. paratyphosus A, B. paratyphosus C, B. suipestifer, or Type “G.” It therefore offers a means of distinguishing the Heading type from B. suipestifer and Type “ G.” We observed no irregularities in the fermentation of this salt by the various types. It will be seen from the foregoing that with the use of six salts: citrate, (/-tartrate, /-tartrate, m-tartrate, fumarate, and mucate, we have succeeded in obtaining seven different cultural groupings from the eleven different Salmonella types. The types we have still failed to differentiate are Mutton, Newport and Binns from one another, and suipestifer from Type “G.'J The following table gives a summary of the reactions with these six salts, and it is convenient at this stage to compare these results with those hitherto obtained from “sugar fermentations. Citrate d-tartrate ^-tartrate m-tartrate fumarate mucate B. paratyphosus A — — — • — B. paratyphosus B + — + • + B. paratyphosus C 4* + — — — B. suipestifer + + — + — Salmonella type “G” + + — + — Type Reading + + — + + Type Mutton + + + + • + Type Newport + + + + • + Type Binns + + + + • + Type Stanley + + + — • + B. enteritidis, Gartner + ± ± ± + + Results were taken at the end of 48 hours incubation at 3 < ° C. except in the case of fumarate, in which the incubation was prolonged to 9(5 hours to allow for its slower decomposition. A + sign indicates complete decomposition of the salt as evidenced by the formation of only a small precipitate consisting chiefly of lead carbonate on the addition of the lead acetate solution. A — sign indicates failure to decompose as evidenced by a bulky precipitate of the lead salt of the undecomposed acid. In the case of fumarate a — sign indicates change of the salt as indicated by a bulky precipitate on addition of lead acetate (cf. p. 12) while a + sign expresses further change as shown by a small precipitate of lead carbonate. For the modified precipitation technique applied in the case of mucate, see above.
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