Part of Thermo Fisher Scientific
Organisms this product works with:
Other products used in the isolation of Listeria monocytogenes :
PALCAM AGAR BASE
a selective and differential diagnostic medium for the detection of Listeria monocytogenes
Columbia Blood Agar Base
Ferric ammonium citrate
pH 7.2 ± 0.2 @ 25°C
PALCAM SELECTIVE SUPPLEMENT
|Product order code|
Volume of medium
10 x 500ml medium
10 x 2.5 litres medium
Suspend 34.5g per 500ml of distilled water. Bring gently to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C, and aseptically add PALCAM Selective Supplement (SR0150), reconstitutes as directed. Mix well and pour into sterile Petri dishes.
The addition of 2.5% (v/v) Egg Yolk Emulsion (SR0047) to the medium may aid the recovery of damaged Listeria.
PALCAM Medium is based on the formulation described by Van Netten et al.1 and is recommended for the isolation of Listeria monocytogenes from foods.
The heightened awareness and concern surrounding the presence of Listeria monocytogenes in food has resulted in the development of many media for its isolation2,3,4,5. However, Cassiday and Brackett6 conclude that no single method currently available at the time was suitable for use with all types of food.
PALCAM Medium is highly selective due to the presence of lithium chloride, ceftazidime, polymyxin B and acriflavine hydrochloride. It allows the easy differential diagnosis of Listeria monocytogenes by utilising the double indicator system.
Listeria monocytogenes hydrolyses aesculin resulting in the formation of a black halo around colonies. Listeria monocytogenes does not ferment mannitol so easy differentiation from contaminants, such as enterococci and staphylococci, can be made as these will ferment mannitol. This formulation produces a change from red to yellow in the pH indicator phenol red. The addition of egg yolk to PALCAM medium has been reported to aid repair of damaged cells3.
Incubation under microaerophilic conditions serves to inhibit strict aerobes such as Bacillus spp. and Pseudomonas spp. that might otherwise appear on the medium. A modification to PALCAM medium in which incubated plates are overlaid with medium containing blood enables haemolytic Listeria spp. to be differentiated and enumerated7. Incubation under microaerobic conditions serves to inhibit strict aerobes such as Bacillus spp. and Pseudomonas spp. that might otherwise appear on the medium.
Techniques for the isolation of Listeria monocytogenes will depend on the material under test. It is usual for the test sample to be first inoculated into an enrichment broth to allow multiplication before isolation and identification. Depending on the type of sample used, the appropriate method and selective enrichment broth should be used prior to inoculation onto PALCAM Medium plates. As a general rule, use Listeria Selective Enrichment Medium (CM0862 and SR0149) for dairy products, and Listeria Selective Enrichment Media UVM ( CM0863, SR0142 and SR0143) and Fraser Broth (CM0895 and SR0156) for meats and poultry.
After 48 hours incubation, typical Listeria spp. form colonies that are approximately 2mm in diameter, grey-green in colour with a black sunken centre and a black halo against a cherry-red medium background. Occasional enterococci or staphylococci develop on PALCAM Medium to forming grey colonies with a brown-green halo or yellow colonies with a yellow halo.
Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the selective supplement in the dark at 2-8°C and use before the expiry date on the label.
The prepared medium may be stored for up to 4 weeks at 2-8°C in the dark.
Dehydrated medium: Straw-coloured, free-flowing powder
Prepared medium: Red gel
|Listeria monocytogenes ATCC® 7644 *|
Good growth; dimpled brown/black coloured colonies with black halo
|Enterococcus faecalis ATCC® 29212 *||Inhibited|
Acriflavine hydrochloride is activated by light which may cause it to become inhibitory to Listeria growth.
1. van Netten P. et al. (1989) Int. J. Food Microbiol. 8. (4) 299-316.
2. Farber J.M. and Peterkin P. (1991) Microbiol. Rev. 55. 476-511.
3. in’t Veld P.H. and de Boer E. (1991) Int. J. Food Microbiol. 13. 295-300.
4. Gunasinghe C.P.G.L. Henderson C and Rutter M.A. (1994) Lett. Appl. Microbiol. 18. 156-158.
5. Lund A.M., Zottola E.A. and Pusch D.J. (1991) J. Food Prot. 54. 602-606.
6. Cassiday P.K. and Brackett R.E. (1989) J. Food Prot. 52. 207-214.
7. van Netten P., van Gaal B. and Mossel D.A.A. (1991) Lett. Appl. Microbiol. 12. 20-22.
8. Bille J. and Doyle M.P. (1991) ``Listeria and Erysipelothrix’’ 287-295 in Balows A., Hausler W.J. Jnr., Herrman K.L. Isenberg H.D. and Shadomy H.J. (Eds) Manual of Clinical Microbiology, 5th Edition, American Society for Microbiology, Washington D.C.