MACCONKEY AGAR WITH MUG

Cat. no. G37 MacConkey Agar with MUG, 15x100mm Plate, 18ml 10 plates/bag

INTENDED USE

Hardy Diagnostics MacConkey Agar with MUG is used for the presumptive identification of Escherichia coli .

SUMMARY

Trepeta and Edberg modified MacConkey Agar by the incorporation of 4-methylumbelliferyl-beta-D-glucuronide (MUG); the resulting medium allowed the authors to presumptively identify Escherichia coli from the primary plating medium within five minutes. (8) The above reaction is possible because most strains of E. coli (96-97%) produce glucuronidase, an enzyme that hydrolyzes MUG to 4-methylumbelliferone. (6) This compound fluoresces under long-wave ultraviolet light (366nm). The addition of MUG to the formulation allows beta-glucuronidase positive strains of E. coli to fluoresce blue-green when examined under this wavelength of UV light.

FORMULA

Ingredients per liter of deionized water:*

Pancreatic Digest of Gelatin 17.0gm
Lactose 10.0gm
Sodium Chloride 5.0gm
Pancreatic Digest of Casein 1.5gm
Peptic Digest of Animal Tissue 1.5gm
Bile Salts No. 3 1.5gm
MUG 0.1gm
Neutral Red 0.03gm
Crystal Violet 0.001gm
Agar 13.5gm

Final pH 7.1 +/- 0.3 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.

PRECAUTIONS

PROCEDURE

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. Follow inoculation and incubation procedures appropriate for specimens being tested. (1,2) After incubation, the medium is examined macroscopically for typical colonies. Colonies of lactose-fermenting bacteria appear brick red to dark pink in color, and may be surrounded by a zone of bile precipitation. Non-lactose-fermenting colonies are colorless. Examine the medium under long-wave ultraviolet light (366nm). Beta-glucuronidase-positive colonies have a blue-green fluorescence. Negative colonies do not fluoresce.

INTERPRETATION OF RESULTS

If pink colonies are seen that fluoresce blue-green under UV light (366nm), it is a presumptive identification for E. coli. Any clear colonies seen, whether they fluoresce or not, are considered a negative result for the presence of E. coli .

LIMITATIONS

Not all strains of Escherichia coli ferment lactose or produce beta-glucuronidase. Some strains of Salmonella and Shigella produce glucuronidase and will fluoresce. A small percentage of Yersinia and streptococci have been reported to fluoresce. (5)

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, long-wave UV lamps, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Pink colonies, surrounding media fluoresces blue-green under UV light (366nm)
Shigella sonnei
ATCC ® 9290
A 24hr 35°C Aerobic Clear colonies, surrounding media fluoresces blue-green under UV light (366nm)
Proteus mirabilis
ATCC ® 12453
A 24hr 35°C Aerobic Clear colonies, no fluorescence under UV light (366nm)
Enterococcus faecalis
ATCC ® 29212
B 24hr 35°C Aerobic Partial to complete inhibition

User Quality Control

Physical Appearance

MacConkey Agar with MUG should appear opalescent, and reddish-purple in color.

Note: This medium contains 4-methylumbelliferyl-beta-D-glucuronide (MUG). Most strains of E. coli possess an enzyme which breaks down MUG to a compound that fluoresces under a long-wave (366nm) ultra violet lamp.

E. coli colonies on MacConkey Agar with MUG under ambient light

Escherichia coli (ATCC ® 25922) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under ambient light. Incubated aerobically for 24 hours at 35ºC.

E. coli colonies on MacConkey Agar with MUG under UV light

Escherichia coli (ATCC ® 25922) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under UV light to demonstrate fluorescence. Incubated aerobically for 24 hours at 35ºC.

E. coli colonies on MacConkey Agar with MUG under ambient light

Shigella sonnei (ATCC ® 9290) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under ambient light. Incubated aerobically for 24 hours at 35ºC.

S. sonnei colonies on MacConkey Agar with MUG under UV light

Shigella sonnei (ATCC ® 9290) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under UV light to demonstrate fluorescence. Incubated aerobically for 24 hours at 35ºC.

E. coli colonies on MacConkey Agar with MUG under ambient light

Proteus mirabilis (ATCC ® 12453) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under ambient light. Incubated aerobically for 24 hours at 35ºC.

P. mirabilis colonies on MacConkey Agar with MUG under UV light

Proteus mirabilis (ATCC ® 12453) colonies growing on MacConkey Agar with MUG (Cat. no. G37). Shown under UV light to demonstrate lack of fluorescence. Incubated aerobically for 24 hours at 35ºC.

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. Feng, P.C.S. and P.A. Hartman. 1982. Appl. Envir. Microbiol.; 43:1320-1329.

4. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

5. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

6. Killian, M. and P. Bulow. 1976. Acta. Pathol. Microbiol. Scand., Sec. B; 84:245-251.

7. Robison, B.J. 1984. Appl. Envir. Microbiol.; 48:1285-288.

8. Trepeta, R.W. and S.C. Edberg. 1984. J. Clin. Microbiol.; 19:172-174.


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032116gr