FRASER BROTH, MODIFIED

Cat. no. K98 Fraser Broth, Modified, 16x125mm Tube, 10ml 20 tubes/box

INTENDED USE

Hardy Diagnostics Fraser Broth, Modified (without ferric ammonium citrate) is recommended for the selective enrichment of Listeria spp. in foods and environmental samples.

This product is not intended to be used for the diagnosis of human disease.

SUMMARY

First described by Murray, Webb, and Swann, Listeria monocytogenes is a widespread problem in the public health and food industry. (6,8) This microorganism can cause human illness and death, particularly in immunocompromised individuals and in the unborn fetus of 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 . (7,10)

Potential vehicles of transmission implicated in the spread of disease include turkey frankfurters, coleslaw, pasteurized milk, Mexican-style and other soft cheeses, paté and pickled pork tongue. Moreover, 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 also possess the ability to grow over a pH range of 5.0-9.6 and can survive in food products with pH levels outside of these parameters. (10)

Hardy Diagnostics Fraser Broth, Modified is based on the formulation of Fraser and Sperber. (7) The media contains pancreatic digest of casein, proteose peptone, and yeast extract as nitrogen, vitamin, and mineral sources. Although the medium contains esculin, the modified formulation does not contain ferric ammonium citrate which normally produces the characteristic blackening when esculin is hydrolized. Ferric ammonium citrate may be added (Fraser Broth Supplement, Cat. no. Z210) to the tube of medium, if desired. More stable ELISA results are obtained when the ferric ammonium citrate is omitted. This media is made selective by the presence of lithium chloride, nalidixic acid, and acriflavine in the formula. The high salt concentration is used to inhibit the growth of enterococci.

FORMULA

Ingredients per liter of deionized water:*

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
Nalidixic Acid 20.0mg
Acriflavine Hydrochloride 24.0mg

Final pH 7.2 +/- 0.2 at 25ºC.

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

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration, discoloration, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

Consult listed references for information regarding sample preparation and processing. (1-4)

To isolate Listeria monocytogenes from processed meats and poultry, the following procedure is recommended by the U.S.D.A:

1. Add 25.0gm of test material to 225ml Modified Listeria Enrichment Broth (Cat. no. U167) and mix or blend thoroughly.

2. Incubate for 20-24 hours at 30ºC.

3. Transfer 0.1ml of the incubated broth to prepared Fraser Broth, Modified medium. Incubate at 35ºC. for 26 +/- 2.0 hours. If desired, add 0.1ml of a filter sterilized solution of 5% aqueous solution of ferric ammonium citrate (Fraser Broth Supplement, Cat. no. Z210).

4. At 24 and 48 hours, streak the prepared Fraser Broth, Modified culture to Modified Oxford Agar (Cat. no. G46) or PALCAM Agar (Cat. no. G149).

5. Incubate the Modified Oxford or PALCAM plates at 35ºC. for 24-48 hours.

INTERPRETATION OF RESULTS

Observe the Modified Oxford Agar plates for round 1mm colonies with a blackening of the surrounding medium. Suspect colonies may be confirmed by CAMP test on 5% Blood Agar (Cat. no. A10), by further biochemical testing, use of a macroscopic tube rapid slide test, or other means of definitive serological identification.

Observe PALCAM plates for the growth of round gray-green colonies with a black precipitate. Rapid slide and macroscopic tube tests can be used for definitive serological identification. Colonies of mannitol-fermenting contaminants, such as staphylococci and enterococci, appear as yellow colonies with a yellow halo.

LIMITATIONS

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

Modified Listeria Enrichment Broth (Cat. no. U167) is a partially selective medium. Growth of some contaminating strains will be markedly, but not completely, inhibited.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, swabs, applicator sticks, other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Listeria monocytogenes
ATCC ® 7644
A 24hr 35°C Aerobic Growth
Staphylococcus aureus
ATCC ® 25923
B 24hr 35°C Aerobic Partial to complete inhibition
Escherichia coli
ATCC ® 25922
B 24hr 35°C Aerobic Inhibited

USER QUALITY CONTROL

Physical Appearance

Fraser Broth, Modified should appear clear, and bright yellow in color.

REFERENCES

1. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

2. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

3. 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.

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

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

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

7. Monk, J.D. et al. 1987. Irradiation inactivation of Listeria monocytogenes and Staphylococcus aureus in low and high-fat frozen and refrigerated ground beef. J. Food Prot.; 57:769-772.

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

9. U.S. Food and Drug Administration. Bacteriological Analytical Manual, AOAC, Arlington, VA.

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

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


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