DEMI FRASER BROTH FOR LISTERIA

Technical Data #5298a / 2005.08.31

Demi-Fraser Broth for Listeria is a liquid selective medium used for cultivation and isolation of Listeria monocytogenes from foods. Esculin hydrolysed by Listeria sp. produces with ferric ammonium citrate a dark brown complex. Nalidixic acid inhibits Gram-negative organisms while acriflavin inhibits Gram-positive organisms.

FORMULA
in grams per liter purified filtered water

Casein Peptone	10,0
Beef Extract	5,0
Yeast Extract	5,0
Sodium Chloride	20,0
Lithium Chloride	3,0
Esculin	1,0
Sodium Phosphate, dibasic	9,6
Potassium Phosphate, monobasic	1,35
Ferric Ammonium Citrate	0,5
Acriflavin	0,012
Nalidixic Acid	0,01

pH 7,2 +/- 0,2 à 25º C

This approximate formula may be adjusted and/or enriched to obtain best results.

PRECAUTIONS
This medium is for laboratory use only.

STORAGE
Store prepared media at 2-8º C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-25º C.

SIGN OF DETERIORATION
Media should not be used if the expiry date has passed. Prepared media should not be used if there are signs of contamination or deterioration. Do not use dehydrated media if it is caked.

DIRECTIONS
Suspend 55,5 g of dehydrated media in 1000 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Dispense into culture tubes or contenants and sterilize at 121º C for 15 minutes. Precipitate may be observed but this does not interfere the performance.

PROCEDURE
Prior to inoculate, the prepared media should be brought to room temperature.

1. Inoculate specimens directly, onto the tubes
2. Incubate at 35º C for 24 hours.
3. Transfer 0,1 ml of the broth on a selective Listeria plate and incubate for another 24 hours at 35º C

QUALITY CONTROL
Results after 24 hrs at 35ºC

Organisms	ATCC	Growth
Listeria monocytogenes	15313	+ blackening
Staphylococcus aureus	25923	- or partiel
Escherichia coli	25922	- or partiel
Enterococcus faecalis	29212	- or partiel

LIMITATIONS OF METHOD
This medium is only a part of the identification. Other tests may be required.

REFERENCES

1. Fraser, J.A. and Sherber, W.H. 1988 Rapid Detection of Listeria in Food and Environmental Samples by Esculin Hydrolysis. J. Food Prot. 51:762-765
2. Donnelly and Baigent 1986 Method for flow cytometric detection of Listeria monocytogenes in milk Appl. Environ. Microbiol. 52 :689-695
3. L'Association française de normalisation AFNOR 1993 Food Microbiology Detection of Listeria monocytogenes-Routine Method V08-055 AFNOR Paris France

CATALOGUE NUMBERS

Dehydrated media	500 g	QB-39-1803
Prepared media
225 ml in 300 ml contenant	10 units	5298

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