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The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change. Sometimes, it is possible to detect growth on the Simmons' citrate agar without the accompanying color change to blue. This should be scored as a negative for the citrate use test. [12]
This results in a change of the medium's color from green (neutral) to blue (alkaline). Bacterial colonies are picked up from a straight wire and inoculated into slope of Simmons citrate agar and incubated overnight at 37 °C. Inoculating from a broth culture is not recommended because the inoculum would be too heavy.
This test uses Simmon's citrate agar to determine the ability of a microorganism to use citrate as its sole carbon and energy source. The agar contains citrate and ammonium ions (nitrogen source) and bromothymol blue (BTB) as a pH indicator. [2] Bromothymol blue was added in order to reduce false positives.
As there are many bacteria that also look like Salmonella on DCA, it is widely recommended that more selective agars are used for the identification of Salmonella, namely xylose lysine deoxycholate (XLD) agar. This growth medium is heat-sensitive and should be poured and cooled as soon as possible after addition of the deoxycholate, otherwise ...
To ensure that the results are accurate, the concentration of bacteria that is added to the agar or broth (the inoculum) must be standardized. This is accomplished by comparing the turbidity of bacteria suspended in saline or broth to McFarland standards —solutions whose turbidity is equivalent to that of a suspension containing a given ...
The test uses the principles of gel electrophoresis to separate out the various types of hemoglobin and is a type of native gel electrophoresis.After the sample has been treated to release the hemoglobin from the red cells, it is introduced into a porous gel (usually made of agarose or cellulose acetate) and subjected to an electrical field, most commonly in an alkaline medium.
DNase agar is used to test whether a microbe can produce the exoenzyme deoxyribonuclease (DNase), which hydrolyzes DNA. Methyl green is used as an indicator in the growth medium because it is a cation that provides an opaqueness to a medium with the presence of negatively charged DNA strands.
TSI agar slant results: (from left) preinoculated (as control), P. aeruginosa, E. coli, Salmonella Typhimurium, Shigella flexneri The Triple Sugar Iron (TSI) test is a microbiological test roughly named for its ability to test a microorganism's ability to ferment sugars and to produce hydrogen sulfide. [1]