Principles and considerations for Voges-Proskauer (V-P) tests.

1, test principle
bacteria in glucose metabolism to produce acetone acid, starting with acetone acid, with fine
strains
different and there are a variety of decomposition pathways, some make acetone acid further decomposition, the generation of meth Acids, acetic acid, lactic acid and other end products, some can make acetone acid dehydration into a neutral final product acetylmethyl carbinol, also known as 3-oxycodone (Acetoin). This test is to check whether certain bacteria produce acetyl methyl methanol in glucose metabolism, as the basis for identification.
Acetyl methyl methanol in alkaline environments can be oxidized into Diacetyl by oxygen in the air, butyl dikontazone and proteincontaining arginine in the role of arginine, the production of red
compound
, that is, V-P test positive.
creatine or creatine can supply more arginine than arginine, so it has the effect of speeding up the positive V-P test.
Without α-phenol, at least 10PPm of butyldicone is required to test positive, adding α-phenol can increase the sensitivity of the V-P test by about 50 times without reducing the specificity of the test, and its alcohol solution also enhances color. In the trial, α-phenol must be added to bind to butyl ketones and nicotine-based compounds before it can be added to a 40% potassium hydroxide solution with an addition of no more than 0.2 ml.
addition order is reversed, potassium hydroxide can react withprotein to produce orange-red and cause false positives. Potassium hydroxide, as an oxidant, accelerates the oxidation of acetyl methyl methanol to butyl diktone and contributes to the absorption of carbon dioxide.
II, the test results judge
than, note
beef dip soup can not be used in this test, because the muscle leaching contains acetyl methyl methanol, butyl glycodone and other substances interfering with the test, can cause false positive.
V-P test-positive bacteria occasionally do not appear positive, in order to avoid this situation, the
cultured
with
reagements
can be added at about 50 degrees C slightly
heating
, the positive bacteria appear red, and the real negative bacteria remain the original color.
In the general
medium
, most of the 1-3 days of culture can be positive, training time is too long, can be due to acid production and make the V-P reaction weakened or caused false negative.
generally speaking, the V-P test and the methyl red test were mostly opposite results. It should be noted, however, that this is not absolute, with a small number of bacteria such as Hafnia alvei and Singular Difficile sometimes testing positive for both.
test is generally used for the identification of various strains of E. coli. When used in other bacteria such as Bacillus spores and staphylococcus, phosphates in general-purpose cultures can hinder the production of acetyl methyl methanol and should be omitted or replaced with sodium chloride.
Regarding the culture temperature of V-P experimental culture, it is generally used at 35 degrees C or 37 degrees C, but some scholars in Japan believe that 37 degrees C culture often makes the enzyme that breaks down acetyl methyl methanol inactive, so it advocates the use of 28-30 degrees C culture, which can be cultivated at room temperature in summer. A small number of bacteria, such as Hafnia E. coli, are known to be often unstable in V-P tests cultured at 37 degrees C and need to be cultured at 25-30 degrees C for reliable results.
, the copyright of
article is owned by Haibo Bio and may not be reproduced without authorization.
.