PRINCIPLE
Medium contains two indicator systems, ferric citrate (esculin hydrolysis) and phenol red (mannitol fermentation).
L. monocytogenes hydrolyzes esculin to form esculetin and dextrose. Esculetin reacts with ammonium ferric citrate and forms a
brown-black complex seen as a black halo around colonies. Gram-negative bacteria are completely inhibited. Other Gram-positives
are inhibited or grow poorly.


PROCEDURE
See ISO 11290-1:1996 Microbiology of food and animal feeding stuffs -- Horizontal method for the detection and enumeration of
Listeria monocytogenes -- Part 1: Detection method, and ISO 11290-2:1998 Microbiology of food and animal feeding stuffs --
Horizontal method for the detection and enumeration of
Listeria monocytogenes -- Part 2: Enumeration method.


RESULTS & INTERPRETATION
Listeria colonies appear as grey-green with a black precipitate, following inoculation and incubation at 35°C for 24-48 hours under
aerobic or microaerophillic conditions.
L. monocytogenes does not ferment mannitol, thus colonies color will not change from red to
yellow.


QUALITY CONTROL
Listeria monocytogenes ATCC 7644 - good growth, brown-black / grey-green colonies with black center and black halo;
Enterococcus faecalis ATCC 29212 - inhibited / poor growth (brown colonies with brown-green halo);
Staphylococcus aureus ATCC 25923 - inhibited / poor growth (yellow colonies with yellow halo).
COMPOSITION
Columbia Blood Agar Base ………….............………………….. 39.0 g
Yeast extract ...…………………………................………………..... 3.0 g
Glucose (dextrose) ...……………...............……………..........…… 0.5 g
Aesculin ………………......................………………………….…… 0.8 g
Ferric ammonium citrate.. …....…………................……………… 0.5 g
Mannitol ............……………....………………..............…………... 10.0 g
Phenol red ……………………….....………….............………….  0.08 g
Lithium chloride …........……………..………..............…………... 15.0 g
Distilled water ad 1000 ml, pH 7.2 ± 0.2.

SELECTIVE SUPPLEMENT (for 500ml base medium)
Polymyxin B .......................................................................... 10.0mg
Acriflavine hydrochloride ....................................................   5.0mg
Ceftazidime .......................................................................... 20.0mg

Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C, and aseptically add the
Selective Supplement.

NOTE
Lithium chloride is harmful. Avoid bodily contact and inhalation of vapours.

Variants of medium replace Columbia Blood Agar Base & yeast extract with:
Peptic digest of animal tissue .................................................... 23.0g
Starch ................................................................................................. 1.0g
Sodium chloride ............................................................................... 5.0g
DESCRIPTION
Polymyxin-Acriflavin-Lithium chloride-Ceftazidime-Aesculin-Mannitol (PALCAM) Agar was formulated by Van Netten et al for the the
isolation of
Listeria monocytogenes and other Listeria from foods.
PALCAM Agar
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