Tryptone Agar, HiVeg™

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SKU:
MV961
Recommnended for rapid detection and enumeration of Escherichia coli in food using a modified direct plating method.


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Composition ** :

Ingredients Grams/Litre
HiVeg hydrolysate 20.0
Synthetic detergent No. I 1.5
Agar 15.0

Final pH (at 25°C) 7.2 ± 0.2

** Formula adjusted, standardized to suit performance parameters.

Directions

Suspend 36.5 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.

Principle and Interpretation :

This medium is prepared by using HiVeg hydrolysate and synthetic detergent which are of vegetable origin, hence the medium is totally free from BSE/TSE risks.

Tryptone Agar, HiVeg is the modification of Tryptone Bile Agar which was formulated by Anderson and Baird-Parker (1). The International Commission on the Microbiological Specifications for Foods (CMSF) (2) compared the Most Probable Number (MPN) and the Anderson-Baird-Parker Direct Plating Method (DPM) using Tryptone Agar and observed that DPM was superior to MPN for enumeration of Escherichia coli from raw meats. Tryptone Agar HiVeg like the conventional medium can be used for direct Plating method. Superiority of DPM method was noticed by the organization on the basis of less variability, better recovery from frozen samples, greater rapidity and the smaller quantity of medium required. It was reported that DPM enumerates both anaerogenic and late lactose fermenting strains of Escherichia coli which could be missed by the MPN method (about 10%) (3). Holbrook et al (4) modified the DPM for detection and enumeration of sublethally damaged cells of Escherichia coli in frozen, dried, heat processed or acid foods and found that resuscitation step reduces the high concentration of sugar present in the inoculum to a level which does not interfere with the production of indole, as the synthesis of tryptophanase is inhibited by high sugar concentrations (5).

The indole positive organisms other than Escherichia coli are inhibited by synthetic detergent and higher incubation temperature of 44°C.

Quality Control :

Appearance of powder
Light yellow coloured, may have slightly greenish tinge, homogeneous, free flowing powder.

Gelling
Firm, comparable with 1.5% Agar gel.

Colour and Clarity
Yellow coloured, clear to slightly opalescent gel forms in petri plates.

Reaction
Reaction of 3.65% w/v aqueous solution is pH 7.2 ± 0.2 at 25°C.

Product Profile :

Vegetable based (Code MV) Animal based (Code M)
MV961 M961
HiVeg hydrolysate Casein enzymic hydrolysate
Synthetic detergent No. I Bile salts mixture

Reconstitution

Quantity on preparation (500g): 36.5 g/l

pH (25°C): 7.2 ± 0.2

Supplement: None

Sterilization: 121°C / 15 minutes.

Storage: Dry Medium - Below 30°C, Prepared Medium 2 - 8°C.

Cultural Response

Cultural characteristics observed after an incubation at 44°C for 24 hours.

Organisms (ATCC) Inoculum (CFU) Growth Recovery
Bacillus subtilis (6633) 102-103 inhibited 0%
Enterococcus faecalis (29212) 102-103 inhibited 0%
Escherichia coli (25922) 102-103 luxuriant >50%
Staphylococcus aureus (25923) 102-103 inhibited 0%

References :

  1. Anderson J.M. and Baird-Parker A.C., 1975, J. Appl. Bact., 39:111.
  2. International Commission on Microbiological Specifications for Food, 1979, Can. J. Microbiol., 25:1321.
  3. Ewing W.H., 1972, US Dept. of Health, Education and Welfare, CRC, Atlanta.
  4. Holbrook R, Anderson J.M. and Baird Parker A.C., 1980, Food Technol. in Aust., 32:78.
  5. Clarke P.H. and Cowen S.T., 1952, J. Gen. Microbiol., 6:187.
More Information
Product Name Tryptone Agar, HiVeg™
SKU MV961
Product Type HiVeg™
Physical Form Powder
Origin Animal Free (Veg)
Packaging type HDPE
References 1. Anderson J. M. and Baird-Parker A. C., 1975, J. Appl. Bacteriol., 39:111.2.International Commission on Microbiological Specifications for Food, 1979, Can. J. Microbiol., 25:1321.3.Ewing W. H., 1972, US Dept. of Health, Education and Welfare, CRC, Atlanta.4.International Organization for Standardization (ISO), 1988, Draft ISO/DIS 6391.5.Holbrook R., Anderson J. M. and Baird - Parker A.C., 1980, Food Technol. in Aust., 32:78.6.Clarke P. H. and Cowen S. T., 1952, J. Gen. Microbiol., 6:187.7.MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. I, Williamsand Wilkins, Baltimore.8.Finegold S. M., Baron E. J., 1986, Bailey and Scotts Diagnostic Microbiology, 7th Ed., The C.V. Mosby Co., St. Louis.
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