CRITERION™ MACCONKEY AGAR WITH SORBITOL

Cat. no. C6170 CRITERION™ MacConkey Agar with Sorbitol 111.5gm
Cat. no. C6171 CRITERION™ MacConkey Agar with Sorbitol 500gm
Cat. no. C6172 CRITERION™ MacConkey Agar with Sorbitol 2kg
Cat. no. C6173 CRITERION™ MacConkey Agar with Sorbitol 10kg
Cat. no. C6174 CRITERION™ MacConkey Agar with Sorbitol 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ MacConkey Agar with Sorbitol is to be used as a selective and differential medium for the detection of enterohemorrhagic Escherichia coliO157:H7.

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

E. coli O157:H7 is an enteric pathogen that typically causes hemorrhagic colitis and bloody diarrheal illnesses. It may be followed by hemolytic uremic syndrome, especially in young children. MacConkey Agar with Sorbitol is recommended for isolation of this organism. Rappaport and Henig first described the formulation of the medium, and it was later confirmed by March and Ratnam who reported MacConkey Agar with Sorbitol to have a sensitivity of 100% and a specificity of 85%. This medium has proved to be an inexpensive, rapid, simple yet reliable means for the detection of E. coli O157:H7.

FORMULA

Gram weight per liter: 58.0gm/L
Pancreatic Digest of Gelatin 18.0gm
Sorbitol 10.0gm
Sodium Chloride 5.0gm
Pancreatic Digest of Casein 4.5gm
Peptic Digest of Animal Tissue 4.0gm
Bile Salts Mixture 1.5gm
Neutral Red 30.0mg
Crystal Violet 1.0mg
Agar 15.0gm

Final pH 7.1 +/- 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 pinkish-beige.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 55.75gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

3. Sterilize in the autoclave at 121ºC. for 15 minutes. Avoid overheating.

4. Cool to 50-55ºC. and dispense approximately 20ml into sterile petri dishes.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G36.

LIMITATIONS

Reading of MacConkey Agar with Sorbitol beyond 24 hours should be avoided since the pink color fades in sorbitol-fermenting colonies. Likewise, an extremely heavy inoculum of sorbitol-fermenters may prematurely exhaust the sorbitol and yield white to off-white colonies.

Other gram-negative organisms are able to grow on MacConkey Agar with Sorbitol, however, colony appearance is generally enough to differentiate these organisms from E. coli O157:H7.

The MacConkey Agar with Sorbitol may be used as an aid in the identification of bacteria.

Sorbitol-negative colonies may be presumptively identified as E. coli O157 using our E. coliPRO™ O157 Kit (Cat. no. PL070HD). Further serotyping with H7 antiserum is necessary for definitive identification (Cat. no. 221591).

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as autoclave, incinerators, and incubators, etc., are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli O157:H7
ATCC® 35150
A 24hr 35°C Aerobic Clear colonies seen; no fermentation of sorbitol
Escherichia coli
ATCC® 25922
A 24hr 35°C Aerobic Pink colonies seen; fermentation of sorbitol

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ MacConkey Agar with Sorbitol powder should appear homogeneous, free-flowing, and light pinkish-beige in color. The prepared media should appear slightly opalescent, and reddish-purple in color.

REFERENCES

1. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

2. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

3. Rappaport, F., E. Henig. 1952. J. Clin. Path.; 5:361.

4. March, S.B., S. Ratnam, et al. 1986. Sorbitol-MacConkey Medium for detection of Escherichia coli O157:H7 associated with hemorrhagic colitis. J. Clin Microbiol.; 23:869-872.

5. March, S.B., S. Ratnam, et al. 1988. Characterization of Escherichia coli serotype O157:H7. J. Clin. Microbiol.; 26:2006-2012.


ATCC is a registered trademark of the American Type Culture Collection.

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