MACCONKEY AGAR WITH SORBITOL (SMAC)
|Cat. no. G36||MacConkey Agar with Sorbitol, 15x100mm Plate, 18ml||10 plates/bag|
|Cat. no. J49||
CIN / MacConkey Agar with Sorbitol, 15x100mm Biplate,
Hardy Diagnostics MacConkey Agar with Sorbitol is to be used as a selective and differential medium for the detection of enterohemorrhagic Escherichia coli O157:H7.
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 Ratham 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.
Ingredients per liter of deionized water:*
|Pancreatic Digest of Gelatin||17.0gm|
|Pancreatic Digest of Casein||1.5gm|
|Peptic Digest of Animal Tissue||1.5gm|
|Bile Salts Mixture||1.5gm|
Final pH 7.1 +/- 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 (shrinking, cracking, or discoloration), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.
Specimen Collection: Consult appropriate references to determine how to correctly collect the specimen to be tested (stool, food, etc.).
Method of Use: Allow plates to warm to room temperature. The agar surface should be dry before inoculating. Inoculate the plates with a suspension of the sample to be tested in a dilution small enough to produce isolated colonies. Incubate plates aerobically at 37ºC. for 24 hours. Examine media macroscopically for typical colonies.
INTERPRETATION OF RESULTS
Colony Morphology: E. coli O157:H7 forms colorless colonies, but otherwise typical of that produced by other E. coli species. Any bacteria capable of fermenting sorbitol (including other E. coli species) form pink colonies on MacConkey Agar with Sorbitol.
The MacConkey Agar with Sorbitol may be used as an aid in the identification of bacteria. Additional biochemical and/or serological testing using pure culture is recommended for complete identification.
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.
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 loops, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.
ATCC ® 35150
|A||24hr||35°C||Aerobic||Clear colonies seen; no fermentation of sorbitol|
ATCC ® 25922
|A||24hr||35°C||Aerobic||Pink colonies seen; fermentation of sorbitol||
ATCC ® 29212
|B||24hr||35°C||Aerobic||Partial to complete inhibition|
User Quality Control
MacConkey Agar with Sorbitol should appear slightly opalescent, and reddish-purple in color.
Escherichia coli O157:H7 (ATCC ® 35150) colonies growing on MacConkey Agar with Sorbitol (Cat. no. G36). Incubated aerobically for 24 hours at 35ºC.
Escherichia coli (ATCC ® 25922) colonies growing on MacConkey Agar with Sorbitol (Cat. no. G36). Incubated aerobically for 24 hours at 35ºC.
Uninoculated plate of MacConkey Agar with Sorbitol (Cat. no. G36).
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. and 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.