On Voges and Proskauer’s reaction for certain bacteria

Abstract

In 1898 Voges and Proskauer described a new colour reaction which they had observed in the case of a bacillus, isolated by Voges and grown in a medium containing sugar. When potash was added and the tube allowed to stand for 24 hours or longer at room temperature, a beautiful fluorescent colour, somewhat similar to that of a dilute alcoholic solution of eosin, formed in the culture fluid, particularly at the open end of the tube exposed to the air. The reaction was found to be specific to the bacillus in question, and was not given by any of the other organisms isolated in the course of the investigation upon which they were engaged, nor by the B. colicommunis , so that it afforded a most valuable means of differentiation for the inhabitants of the intestine. Durham and How have also employed this reaction for the discrimination of intestinal bacteria, and MacConkey, in confirmation of Durham, has found that out of a large number of bacteria which were tested only three gave the reaction, these being B. lactis aerogenes (Escherich), B. capsulatus (Pfeiffer), and B. cloacæ (Jordan). The examination of the products formed by B. lactis aerogenes from glucose has shown that acetylmethylcarbinol, CH 3 .CO.CH(OH).CH 3 , and 2·3-butyleneglcol, CH 3 .CH(OH).CH(OH).CH 3 , are both present in the medium in which this has been cultivated in the presence of glucose. The acetylmethylcarbinol has not as yet been isolated in the pure state, but is present in the aqueous distillate obtained by distilling the culture medium. This disllate and the glycol were, therefore, treated with caustic potash in order to ascertain whether either of them was the cause of the reaction just described. Neither of there substances produces the characteristic fluorescent coloration with potash alone, but when peptone water is also added, acetylmethylcarbinol gives the reaction after standing for about 24 hours, whilst the glycol does not react in this way even on standing. The colaration was produced in the characteristic manner described by Voges and Proskauer, commencing at the open end of the tube exposed to the air. This suggests oxidation as a factor in the phenomenon, and as acetylmethylcarbinol is very readily converted by oxidation into diacetyl, CH 3 .CO.CO.CH 3 , this substance was tested. Diacetyl yields the fluorescent red coloration with peptone water and caustic potash in a few minutes, and by its aid a much greater depth of colour can be obtained than that observed with bacterial cultures.