MAC CONKEY SORBITOL AGAR

Technical Data #1657a / 2013.06.11

The Mac Conkey Sorbitol Agar is a differential solid medium used for the cultivation and isolation of Escherichia coli serotype 0157:H7 associated with epidemics of hemorrhagic colitis. Colonies of E. coli serotype O157:H7 are clear because this bacteria does not ferment sorbitol as does other type of E. coli, whose colonies are red.

 


 

FORMULA
in grams per liter purified filtered water

Gelatin Peptone

17,0

Casein Peptone

1,5

Meat Peptone

1,5

Bile Salts

1,5

Sorbitol

10,0

Sodium Chloride

5,0

Neutral Red

0,03

Crystal violet

0,001

Agar

13,5

pH 7.1 +/- 0,2 25 C

This approximate formula may be adjusted and/or enriched to obtain best results.


PRECAUTIONS
This medium is for IN VITRO diagnostic use only.


STORAGE
Store prepared media at 2-8 C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-25 C.


SIGN OF DETERIORATION
Media should not be used if the expiry date has passed. Prepared media should not be used if there are signs of contamination or deterioration (shrinking, cracking, evaporation or discoloration). Do not use dehydrated media if it is caked.


DIRECTIONS
Suspend 50 g of dehydrated media in 1000 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Sterilize at 121 C for 15 minutes. Cool to 45-50 C. Mix gently and dispense into sterile Petri dishes.


PROCEDURE
Prior to inoculate, the prepared media should be brought to room temperature.

  1. Directly, inoculate plate as soon as possible with specimen and streak for isolation. If inoculation will be delayed, an Enteric Pathogen Transport Medium as EPT-100 should be used.
  2. Incubate at 35 C for 24 hours.


QUALITY CONTROL

Results after 24 hrs at 35C

Organisms

ATCC

Growth

Colour

Escherichia coli 0157:H7

35150

+

colorless

Escherichia coli

25922

+

red

Enterococcus faecalis

29212

- or partial

 

Colonies of E. coli serotype O157:H7 appear on Mac Conkey Sorbitol Agar as colourless colonies non-sorbitol fermenter. Others E. coli, sorbitol fermenters, give red colonies and gram-negative non-sorbitol fermenters appear translucent.


LIMITATIONS OF METHOD
This medium is only a part of the identification. Other tests may be required to differentiate gram-negative non-sorbitol fermenters from E. coli serotype O157:H7.


REFERENCES

  1. Lennette, E.H., Ballows, A., Hausler, W.J.Jr., and Shadomy, H.J. Manual of Clinical Microbiology. 4th ed. 1985 Washington D.C.: American society for Microbiology.
  2. March, B.S. and Ratnam, S., 1986 Sorbitol Mac Conkey Medium for Detection of Escherichia coli O157:H7 associated with hemorrhagic colitis. J. Clin. Microbiol. 23:869-872.
  3. Farmer, J.J. III. and Davis, B.R., 1985 H7 Antiserum-Sorbitol Fermentation Medium: a single tube screening medium for detecting Escherichia coli O157:H7 associated with hemorrhagic colitis. J. Clin. Microbiol. 22:620-625.
  4. Wells, J.G., B.R. Davis, I.K. Wachsmuth, L.W. Riley, R.S. Remis, R. Sokolow, and G.K. Morris. 1983 Laboratory investigation of hemorrhagic colitis outbreaks associated with a rare Escherichia coli serotype. J. Clin. Microbiol. 18: 512-520.


CATALOGUE NUMBERS

Dehydrated media 500 g QB-39-2710
     
Prepared media    
Plates, 100x15 mm 10/pkg 1657
Mono-Plates, 100x15 mm 10/pkg 1657M
     
Enteric Pathogen Transport, Vial 100/cs EPT-100

 


 





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