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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]
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.
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.
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]
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.
Thiosulfate–citrate–bile salts–sucrose agar, or TCBS agar, is a type of selective agar culture plate that is used in microbiology laboratories to isolate Vibrio species. [1] TCBS agar is highly selective for the isolation of V. cholerae and V. parahaemolyticus as well as other Vibrio species. Apart from TCBS agar, other rapid testing ...
DCA agar (deoxycholate citrate agar) is a solid bacteriological growth medium used for isolation of enteric pathogens. [1] Uses
The plates are incubated for 12 hours up to several days, depending on the test that is performed. Commonly used types of agar plates include: Red blood cells on an agar plate are used to diagnose infection. On the left is a positive Staphylococcus infection, on the right a positive Streptococcus culture.