Marica D, Kadar I, Rudăreanu N, Corlătean M, Miclea I, Bologa O
Facultatea de medicină veterinară, Laboratorul Microbiologie-Imunologie, Cluj-Napoca.
Bacteriol Virusol Parazitol Epidemiol. 1990 Apr-Jun;35(2):161-7.
According to the authors of the present paper, the formation of the MR+ and MR- groups is not explained by the variable degree of acidification, but by the various capacity of realkalinization of cultures. pH increases to values tending to 8 due to the formation of amines, ammonia and other basic products. They are the result of oxidative degradation processes, thus explaining the dependence on oxygen and the strictly aerobic character of the reaction. The acid-alkaline variation is influenced by the different content of peptones in monoaminodicarboacylic (meat-contraindicated) and diaminomenocarvoxylic (casein/soya bean-recommended) acids. The alkaline reversion may be determined in liquid media, having included ab initio either bromthymol blue, or bromcresol purple. The changes in pH may be read directly, colorimetrically, after an 18-20-hour incubation. By changing the interpretation (acid from glucose) and the indicator suggested by Clark and Lubs, the name "methyl red" becomes meaningless. At the same time, the introduction of other biochemical parameters (proteinic catabolism, realkalinization, dependence on oxygen) and the modification of the conditions of methods, justify the suggestion that the process of alkaline reversion, noted by the abbreviation "Reval", should be considered as a "per se" reaction and the laboratory determination should be patented as a routine test for the diagnosis of Enterobacteria.
