| Phenylalanine Deamination |
DESCRIPTION
The test check the ability of bacteria to deaminate phenylalanine into phenylpyruvic acid. After incubation, the medium is covered with
ferric chloride solution, which will react with the phenylpyruvic acid and produce a dark green color. Phenylalanine Agar is used
mostly for the differentiation of Enterobacteriaceae (Proteus, Providencia, Morganella & Tatumella give positive results).
The test check the ability of bacteria to deaminate phenylalanine into phenylpyruvic acid. After incubation, the medium is covered with
ferric chloride solution, which will react with the phenylpyruvic acid and produce a dark green color. Phenylalanine Agar is used
mostly for the differentiation of Enterobacteriaceae (Proteus, Providencia, Morganella & Tatumella give positive results).
MEDIUM PREPARATION
Phenylalanine Agar composition:
DL-Phenylalanine ........................................................... 2.0 g
Yeast Extract .................................................................... 3.0 g
Sodium Chloride ............................................................ 5.0 g
Dipotassium Phosphate .............................................. 1.0 g
Agar ................................................................................ 12.0 g
H2O ad 1000 ml.
Adjust pH to 7.3 ± 0.2 (25 °C). Autoclave at 121°C for 15 minutes.
Medium aspect: yellow / light amber, slightly opalescent.
Dispense in tubes for slant cultures.
Ferric chloride solution preparation:
Fe2Cl6 ............................................................................... 10 g
Distilled water ............................................................ 100 ml
PROCEDURE
Inoculate Phenylalanine Agar slant tubes and incubate aerobically at 35-37°C. After
18-24 hours of incubation add few drops of ferric chloride solution. This will combine
with the phenylpyruvic acid forming a dark green layer on the surface of the medium
and in the liquid from the bottom within 1-5 minutes, if the reaction is positive.
Reaction is negative if medium remains yellow..
Phenylalanine Agar composition:
DL-Phenylalanine ........................................................... 2.0 g
Yeast Extract .................................................................... 3.0 g
Sodium Chloride ............................................................ 5.0 g
Dipotassium Phosphate .............................................. 1.0 g
Agar ................................................................................ 12.0 g
H2O ad 1000 ml.
Adjust pH to 7.3 ± 0.2 (25 °C). Autoclave at 121°C for 15 minutes.
Medium aspect: yellow / light amber, slightly opalescent.
Dispense in tubes for slant cultures.
Ferric chloride solution preparation:
Fe2Cl6 ............................................................................... 10 g
Distilled water ............................................................ 100 ml
PROCEDURE
Inoculate Phenylalanine Agar slant tubes and incubate aerobically at 35-37°C. After
18-24 hours of incubation add few drops of ferric chloride solution. This will combine
with the phenylpyruvic acid forming a dark green layer on the surface of the medium
and in the liquid from the bottom within 1-5 minutes, if the reaction is positive.
Reaction is negative if medium remains yellow..
REFERENCES
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Dumitru Buiuc, Marian Negut, 2009. Tratat de microbiologie clinica ed III. 1138.
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Dumitru Buiuc, Marian Negut, 2009. Tratat de microbiologie clinica ed III. 1138.
| Phenylalanine agar, positive left, negative right |
Quality controls:
Positive controls: Proteus vugaris, Providencia alcalifaciens.
Negative control: Salmonella enterica serovar enteritidis, Enterobacter aerogenes.
Positive controls: Proteus vugaris, Providencia alcalifaciens.
Negative control: Salmonella enterica serovar enteritidis, Enterobacter aerogenes.
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