[The effect of the type of peptone for protein catabolism and realkalinization in Klebsielleae cultures]. / Influenta tipului de peptona pentru catabolismul proteinic si realcalinizarea culturilor la Klebsielleae.

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.

[Aerobic conditions and the dynamics of the methyl red reaction in Klebsielleae]. / Conditionarea aeroba si dinamica reactiei rosului de methyl la Klebsielleae.

The development of the methyl red reaction (MR) in Klebsielleae, analyzed during a 4-day thermostatting, showed important pH-variations. Two steps are distinguished during the reaction dynamics: the former of acidification, common to all Enterobacteriaceae and the latter of alkaline reversion, specific to Enterobacter, Klebsiella, Serratia and other MR germs. The processes determining the alkaline reversion are conditioned by the presence of large amounts of air/oxygen (aerobic processes). In this situation, the lack of oxygen and maintenance of a relative degree of anaerobiosis block realkalinization (media covered with paraffin oil) whereas the large aeration stimulates it (optimum ratio between the large contact surface and a small volume of medium). Alkaline reversion cannot be explained by the more or less intense process of glucose fermentation but by degradations of nitrogenized substances with formation of amines, ammonia, and other basic compounds. That is why the analysis of the reaction mechanism of methyl red has to consider the characteristics of the catabolism of the nitrogenized substances and the intense realkalinization capacity of the culture medium proper to Klebsielleae but poorly expressed and non efficient in Enterobacteriaceae.

[Changes in the antibacterial activity of nitrofurantoin preparations induced by peptone and hydrolysates]. / Modificari in activitatea antibacteriana a preparatului nitrofurantoin determinate de peptona si hidrolizate.

The determination of the activity of the product nitrofurantoin (10 and 100 mcg) versus 324 strains of Gram-negative bacteria showed that the diameter of the inhibition zones and the MIC values on a medium with a definite composition (7SG) are considerably larger than on the Mueller-Hinton (MH) medium, in the bacto-tryptose (BT) medium. An increase with 8-12 mm phi or with 2-4 binary dilutions changes the interpretation from resistant, on the MH and BT media into sensitive on the 7SG medium. The low results recorded on the conventional media reveal the existence of an antagonism between peptone and nitrofurantoin, similar to that known for sulfamides. The authors believe that the peptone antagonism has hindered the knowledge of the activity of the nitrofurfural derivatives and the correct assessment of the bacteria sensitivity. They also consider questionable the elimination tendency of the small dosage of microtablets of nitrofurantoin (10 mcg) and sulfamide (30 mcg), since their apparent insufficiency might be due less to the inadequate contraction of substances and more to the inadequate testing media. The results plead for the use of the media with definite chemical composition sulfamide and nitrofuran antagonists free and for reconsideration of several methodologic problems: use of the media with definite chemical composition; introduction of an intermediary dosage of maximum 100 mcg/microtablet; reassessment of the sensitivity categories for sulphafurazole and nitrofurantoin.