Print Friendly View
Rose Bengal Agar Base

Catalog Number: 1008917
Rose Bengal Agar Base


Description: Rose Bengal Agar Base and Chloramphenicol are used in the preparation of Rose Bengal Chloramphenical Agar. The complete medium is recommended in the selective isolation and enumeration of yeasts and molds from environmental materials and foodstuffs.

Rose Bengal Agar Base is a selective basal medium which supports good growth of yeasts and molds. The pH of the medium is near neutrality for improved growth and recovery of acid sensitive strains.4,5,11 The presence of rose bangal in the base suppresses the growth of bacteria and restricts the size and height of mold colonies.8,10,11 This restriction in growth of molds aids in the isolation of slow-growing fungi by preventing their overgrowth by more rapidly growing species. In addition, rose bengal is taken up by yeast and mold colonies thereby facilitating their recognition and enumeration. Supplementation of Rose Bengal Agar Base with chloramphenicol provides for improved inhibition of bacteria present in environmental materials and foodstuffs.

Formulation in g/L:

Peptone, soybean5 gDextrose10 g
Monopotassium Phosphate1 gMagnesium Sulfate0.5 g
Rose Bengal0.05 gAgar15 g

Preparation:


For the Chloramphenicol supplement:

Preparation of the Rose Bengal Chloramphenicol Agar:

Inoculation and Incubation:

Results:

User Quality Control:
  1. Examine the agar base for color and texture. The powder should be beige to faint pink, free-flowing and homogenous.
  2. Determine the pH of the base after preparation and cooling to 25oC. The pH should be 7.2 + 0.2.
  3. Examine the lyophilized and rehydrated chloramphenicol for evidence of deterioration.
  4. Check the performance of the base and chloramphenicol by testing in the complete medium. Plates should be inoculated with approximately 100 colony forming units of the cultures listed below and incubate aerobically at 20-25oC. Examine plates for growth after 5 days incubation. Results should be as stated below:
OrganismGrowth (after 5 days incubation)Colonial Morphology (after 5 days)
Candida albicans ATCC 10231goodcolonies appear pink, smooth, pasty and raised.
Aspergillus niger ATCC 1015goodcolonies appear white and filamentous becoming salt and pepper and eventually black.
Escherichia coli ATCC 25922marked to complete inhibition
--
Micrococcus luteus ATCC 10240marked to complete inhibition
--

Limitations of the Procedure:
  1. Rose Bengal Agar Base and chloramphenicol are intended for use in the preparation of rose bengal chloramphenicol agar. Although this medium is selective primarily for fungi, microscopic examination is recommended for presumptive identification. Biochemical testing using pure cultures is required for complete identification. Consult appropriate references for further information.12-14
  2. Due to the selective properties of this medium and the type of specimen being cultured, some strains of fungi may be encountered that fail to grow or grow poorly on the complete medium; similarly some strains of bacteria may be encountered that are not inhibited or only partially inhibited.

Availability:

Catalog NumberDescriptionSize
1008917Rose Bengal Agar Base500 g
194787Chloramphenicol, g-Irradiated10 mg
20 mg

References:
  1. Waksman, S.A., "A method for counting the number of fungi in the soil." J. Bact., v. 7: 339-341 (1922).
  2. Koburger, J.A., "Yeasts and molds," p. 225-229. In M.L. Speck (ed.), Compendium of methods for the microbiological examination of foods. American Public Health Association, Inc. Washington, D.C. (1976).
  3. Mossel, D.A.A., M. Visser, and W.H.J. Mengerink, "A comparison of media for the enumeration of molds and yeasts in foods and beverages." Lab Practice, v. 11: 109-112 (1962).
  4. Martin, J.P., "Use of acid, rose bengal and streptomycin in the plate method for estimating soil fungi." Soil Sci., v. 69: 215-232 (1950).
  5. Koburger, J.A., "Fung in foods. IV. Effect of plating medium pH on counts.", J. Milk Food Technol., v. 35: 659-660 (1972).
  6. Tyner, L.E., "Effect of media compositions on the numbers of bacterial and fungal colonies developing in Petri plates." Soil Sci., v. 57: 271-274 (1944).
  7. Smith, N.R., and V.T. Dawson, "The bacteriostatic action of rose bengal in media used for th eplate counts of soil fungi." Soil Sci., v. 58: 467-471 (1944).
  8. Cooke, W.B., "The use of antibiotics in media for the isolation of fungi from polluted water." Antibiotics and Chemotherapy, v. 4: 657-662 (1954).
  9. Papavizas, G.C., and C.B. Davey, "Evaluation of various media and antimicrobial agents for isolation of soil fungi." Soil Sci., v. 88: 112-117 (1959).
  10. Overcast, W.W., and D.J. Weakley, "An aureomycin-rose bengal agar for enumeration of yeast and mold in cottage cheese." J. Milk Technol., v. 32: 442-445 (1969).
  11. Jarvis, B., "Comparison of an improved rose bengal-chlortetracycline agar with other media for the selective isolation and enumeration of molds and yeasts in foods." J. Appl. Bact., v. 36: 723-727 (1973).
  12. Speck, M.L. (ed.), Compendium of methods for the microbiological examination of foods. American Public Health Association, Washington, D.C. (1976).
  13. Marth, E.H. (ed.), Standard methods for the examination of dairy products, 14th Ed. American Public Health Association, Washington, D.C. (1978).
  14. Greenberg, A.E., J.J. Connors, and D. Jenkins (ed.), Standard methods for the examination of water and wastewater, 15th ed., American Public Health Association - American Water Works Association - Water Pollution Control Federation, Washington, D.C. (1981).