The evolution of the methyl rot reaction (MRT), expressed by the pH dynamics in the first 18 hours was examined. A medium made of caseine or soya hydrolysate distributed in small volumes, was experimented versus a control broth made of meat peptone (Clark-Lubs). For Klebsiella the results showed that in the control group the pH acidifies and remains low, thus mimicking a positive reaction. In the caseine/soya medium, a decrease of pH at 4-8 hours is first noticed. Initial acidification, consecutive to glucose fermentation, is then counteracted by another type of processes that change the reaction direction. pH increases at 12-18 hours towards neutrality hat can be easily exceeded in 24 hours. Alkaline reversion is favoured by: a--the richer content in aa diaminomonocarboxylic and b--assurance of a large aeration by increase of the ratio between surface and volume. For evidencing realkalinization, characteristic of Klebsiellae, the medium with caseine/soya, including "ab initio" either Bromkresolpurpur (pH = 5.2-6.2) or Bromtimolblau (pH = 6.7-7.6) is experimented. The medium ensures the direct reading of the reaction, at 18-24 hours, by the colour change. The results correspond to metric pH recording. When the results are not clear (slowly metabolic strains), the culture may be reincubated, an important advantage versus the Clark-Lubs procedure.

Azo Compounds↗

PubMedDate not supplied

[The efficiency of an original selective medium in isolating and identifying gram-negative bacteria in urinary tract infections].

The authors examined 449 samples of urine, bacteriologically important for the minor infection, collected from the patients with clinical forms of urinary infection. Using a selective medium--CMV, enteric agar (Romanian patent--9345/1989), 567 strains of gram-negative germs, chemically belonging to group I (Enterobacteria)-475/83.77%, or to groups II-VI, 66/11.64% were isolated. Other 20 strains, 4.69% could not be identified. Of the total of samples, 333/74.16% were with monobacterial flora versus 116/25.83% samples with pluribacterial flora referring to Enterobacteria associated among them--64/55.17% or to Enterobacteria associated to other gram-negative germs--33/30.17%. Likewise, double or multiple associations among the germs outside the Enterobacteriaceae family were found. The results showed the etiologic participation of 22 bacterial species to which other nonidentified gram-negative microorganisms were added. Our data, more comprehensive than the mentions of the other authors show the efficiency of the culture medium experimented. It has the following advantages: the isolated colonies have a wide chromatic and structural range, showing, in fact, the reactions between the bacterial enzymes and the substances belonging to the medium;--it identifies directly, in the isolation slides, some frequently met species;--it guides sensibly the pricking out; it permits the establishment of the proportion among the types of colonies.

Bacteriuria↗

PubMedDate not supplied

[The effect of the type of peptone for protein catabolism and realkalinization in Klebsielleae cultures].

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.

Bacterial Proteins↗

PubMedDate not supplied

[Aerobic conditions and the dynamics of the methyl red reaction in 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.

Aerobiosis↗

PubMedDate not supplied

[Electron microscopic observations on the existence of "deflagellation tolerance" processes capable of explaining the selective isolation of vibrios in semisolid agar].

The authors identified a group of substances (flagellar depression factors--FDF) which suppress the mobility of enterobacteria (immobilization) but do not influence the Vibrio movements (tolerance). FDF do not affect the vital processes, multiplication and formation of colonies. Electron microscopic interpretation showed that, in the usual media, enterobacteria have characteristic peritrichous cilia, whereas in media with FDF they are denuded of their flagellation formation. As such a process of flagellation depletion seems to be not known, we suggest the term "deflagellation" to name it. In a completely different way, the vibrios keep their single cilium located apically and implicitly their moving ability. These behaviour differences are evident in semisolid agar with FDF. The deflagellated enterobacteria are, therefore, immobilized, and multiply, forming small punctual colonies, of 0.5-1 mm phi, whereas the vibrios tolerating FDF develop and at the same time move in the liquid agar, mass, forming large colonies, of 8-14 mm phi. The electron microscopic observations presented show the existence of a "deflagellation tolerance" process and also explain the specific typology of the colonies of vibrios and enterobacteria formed in liquid agar with FDF.

Agar↗