CRITERION™ HALF FRASER BROTH BASE

Cat. no. C8040 CRITERION™ Half Fraser Broth Base 110gm
Cat. no. C8041 CRITERION™ Half Fraser Broth Base 500gm
Cat. no. C8042 CRITERION™ Half Fraser Broth Base 2kg
Cat. no. C8043 CRITERION™ Half Fraser Broth Base 10kg
Cat. no. C8044 CRITERION™ Half Fraser Broth Base 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Half Fraser Broth Base is used with Fraser Broth Supplement for the selective enrichment and detection of Listeria spp. The medium is also used in conjunction with Fraser Broth Supplement for the rapid detection of Listeria from food and environmental samples.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.

SUMMARY

First described by Murray, Webb and Swann, Listeria monocytogenes is a widespread problem in public health and the food industries.(3,8) This organism can cause human illness and death, particularly in immunocompromised individuals and pregnant women. The first reported food-borne outbreak of listeriosis was in 1985. Since then, microbiological and epidemiological evidence from both sporadic and epidemic cases of listeriosis has shown that the principal route of transmission is via the consumption of foodstuffs contaminated with Listeria monocytogenes.(1,4)

Implicated vehicles of transmission include turkey frankfurters, coleslaw, pasteurized milk. Mexican-style and other soft cheeses, pate' and pickled pork tongue. The organism has been isolated from commercial dairy and other food processing plants. It is ubiquitous in nature, being present in a wide range of unprocessed foods and in soil, sewage, silage and river water. Listeria species grow over a pH range of 5.0-9.6 and survive in food products with pH levels outside these parameters.(1)

Half Fraser Broth Base is a modification of Fraser Broth Base in which the nalidixic acid and acriflavine concentrations have been reduced to 10.0mg/L and 12.5mg/L respectively, in accordance with AFNOR guidelines.(10) It contains pancreatic digest of casein, proteose peptone, and yeast extract as nitrogen, vitamin, and mineral sources. Differentiation is aided by including ferric ammonium citrate in the final medium. Since all Listeria species hydrolyze esculin, the addition of ferric ions to the medium will detect the reaction. Ferric ions, combined with esculetin, produce a dark brown to black color change in the medium surrounding the colonies.

Selectivity is provided by the presence of lithium chloride, nalidixic acid, and acriflavine in the formula. The high salt tolerance of Listeria is used as a means to inhibit growth of enterococci.

FORMULA

Gram weight per liter: 55.0gm/L
Sodium Chloride 20.0gm
Disodium Phosphate 9.6gm
Proteose Peptone 5.0gm
Pancreatic Digest of Casein 5.0gm
Beef Extract 5.0gm
Yeast Extract 5.0gm
Lithium Chloride 3.0gm
Monopotassium Phosphate 1.35gm
Esculin 1.0gm
Acriflavine Hydrochloride 12.5mg
Nalidixic Acid 10.0mg

Final pH 7.2 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original light beige.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 55.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat while stirring to dissolve completely. Avoid overheating.

3. Distribute and autoclave at 121ºC. for 15 minutes.

4. Cool to room temperature. Aseptically add enrichment, 10ml of a filter sterilized 5% aqueous solution of ferric ammonium citrate (Fraser Broth Supplement, Cat. no. Z210).

5. Dispense as desired into sterile containers.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references.

LIMITATIONS

Since the nutritional requirements of organisms vary, some strains of Listeria may be encountered that fail to grow or grow poorly on this medium.

CRITERION™ Half Fraser Broth Base is a partially selective medium. Growth of some contaminating strains will be markedly but not totally inhibited.

Poor growth and a weak esculin reaction may be seen after 40 hours incubation for some enterococci.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as autoclaves, Fraser Broth Supplement (Cat. no. Z210), incinerators, and incubators, etc., are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Listeria monocytogenes
ATCC ® 19114
A 24-48hr 35°C Aerobic Growth; positive esculin reaction (blackening)
Enterococcus faecalis
ATCC ® 29212
B 24-48hr 35°C Aerobic Partial to complete inhibition
Escherichia coli
ATCC ® 25922
B 24-48hr 35°C Aerobic Partial to complete inhibition

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Half Fraser Broth Base powder should appear homogeneous, free-flowing, and light beige in color. The prepared media should appear clear to slightly opalescent, with a fine precipitate, and medium amber in color.

REFERENCES

1. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. APHA, Washington, D.C.

2. International Dairy Federation. 1990. Milk and milk products - detection of Listeria monocytogenes. IDF Provisional International Standard No. 143. International Dairy Federation, Brussels.

3. Murray, E.G, et al. 1926. A disease of rabbits characterized by large mononuclear leucocytosis caused by a hitherto undescribed bacillus Bacterium monocytogenes. J. Path. Bact.; 19:407-439.

4. Monk, J.D, et al. Irradiation inactivation of Listeria monocytogenes and Staphylococcus aureus in law and high-fat frozen and refrigerated ground beef. J. Food Prot.; 57:769-772.

5. Wehr, H.M. 1987. Listeria monocytogenes - a current dilemma Special Report. J. Assoc. Anal. Chem.; 80:769-7762.

6. Grau, F.H., et al. 1995. Occurrence, numbers, and growth of Listeria monocytogenes on some vacuum-packaged processed meats. J. Food Prot.; 55:4-4.

7. Kramer, P.A., et al. 1969. Media selective for Listeria monocytogenes. J. Appl. Bacteriology; 32:381-394.

8. Lovett, J.D., et al. 1987. Listeria monocytogenes. J. Food Prot.; 50:188-192.

9. Lee, W.H., et al. 1994. Laboratory Communication No. 57 (revised February 8, 1994), U.S.D.A., F.S.I.S. Microbiology Division, Bethesda, MD.

10. L'association franciase de normalisation (AFNOR). Food Microbiology - Detection of Listeria monocytogenes - Routine Method, V 08-055. AFNOR, Paris, France, 1993.


053116gr