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Inoculating from a broth culture is not recommended because the inoculum would be too heavy. If the organism has the ability to use citrate, the medium usually changes its color from green to blue, though growth on the medium even without colour change is considered a positive result. [1] An observation of no growth is a negative result.
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. The citrate agar is green before inoculation, and turns blue, because of BTB as a positive test indicator, meaning citrate is utilized.
It is a defined, selective and differential medium that tests for an organism's ability to use citrate as a sole carbon source and ammonium ions as the sole nitrogen source. After citrate enters a cell through citrate permeases, citrate lyase cleaves it into acetate and oxaloacetate, which is further broken down into carbon dioxide and pyruvate ...
Klebsiella aerogenes, [2] previously known as Enterobacter aerogenes, is a Gram-negative, oxidase-negative, catalase-positive, citrate-positive, indole-negative, rod-shaped bacterium. [3] Capable of motility via peritrichous flagella, [4] it is approximately one to three microns in length.
Positive for the phenylalanine test and the Harnstoff urea test P. vulgaris can test positive or negative for citrate. All combine for a Biocode ID of 31406, (Biocode ID 31402, 31404, 31407 all resulting in P. vulgaris with asymptomatic results) for use in the Interpretation Guide/Computer Coding and Identification System.
The species C. amalonaticus, C. koseri, and C. freundii can use citrate as a sole carbon source. Citrobacter species are differentiated by their ability to convert tryptophan to indole (C. koseri is the only citrobacter to be commonly indole-positive), ferment lactose (C. koseri is a lactose fermentor), and use malonate.
DCA agar (deoxycholate citrate agar) is a solid bacteriological growth medium used for isolation of enteric pathogens. [1] Uses
[9] [4] Citrate is used by S. marcescens to produce pyruvic acid, thus it can rely on citrate as a carbon source and test positive for citrate utilization. [4] In identifying the organism, one may also perform a methyl red test, which determines if a microorganism performs mixed-acid fermentation. S. marcescens results in a