LEVINE AGAR (EMB)
CAT Nº: 1050
For the isolation and differentiation of Enterobacteria from clinical samples
FORMULA IN g/l
Gelatin Peptone
10.00
Eosin Y
0.40
Lactose
10.00
Methylene Blue
0.065
Dipotassium Phosphate
2.00
Bacteriological Agar
15.00
Final pH 7.1 ± 0.2 at 25ºC
Escherichia coli
PREPARATION
ATCC 25922
Suspend 37.5 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent
agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121ºC for 15 minutes. Cool to 45-50ºC,
mix well and dispense into plates. The prepared medium should be stored at 8-15°C. The color is purple-blue.
The dehydrated medium should be homogeneous, free-flowing and pink-reddish in color. If there are any physical
changes, discard the medium.
USES
LEVINE AGAR (EMB) is a slightly selective medium for the investigation and differentiation of lactose-fermenting and
lactose non-fermenting Enterobacteria in foods, dairy products and clinical samples. It is used for the examination of
samples of sanitary importance for the presence of coliforms.
Gelatin Peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable
carbohydrate providing carbon and energy. Eosin Y and Methylene blue are inhibitors of Gram positive bacteria.
Bacteriological agar is the solidifying agent.
Coliforms, being lactose-fermenting organisms, are identified as blue-black colonies, and colonies of Salmonella and
Shigella, being lactose non-fermenters, are colorless, transparent or amber.
It is also used for the isolation and identification of Candida albicans. Inoculate medium with sample and incubate at 35
± 2ºC for 18 – 48 hours. See Table of Colony Morphology. The suspect clinical material such as sputum, expectorations,
oral or vaginal secretions, and skin and nail scrapings are streaked on the surface of the Levine Agar (EMB), which
contains added Tetracycline. After 24 - 48 hours of incubation at 35°C in an atmosphere of approximately 10% CO2
colonies appear feathery or similar to a "spider web". As the method is not always uniform, check for the production of
chlamydospores in special media at the same time, such as Biggy Agar (Cat. 1006) and Czapek-Dox Agar (Cat. 1015),
and conduct rapid tests for sugar fermentations.
CHARACTERISTICS OF THE COLONIES
1
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Escherichia coli: 2 - 3 mm in diameter. Blue-black in the center,
Enterobacter aerogenes: Large, 4 - 6 mm in diameter.
Salmonella and Shigella: Transparent, amber to colorless
Proteus: When there is no swarming, similar to Salmonella or
Shigella.
Staphylococcus: (coagulase-positive): Punctiform, colorless
Candida albicans: After 24 - 48 hours at 35°C in 10% CO2.
with edges clear to transmitted light, often with a metallic green
sheen with reflected light.
Elevated and mucoid. Grayish-brown in the center to transmitted
light. Generally does not have a metallic sheen.
Feathery or in the form of a spider web.
Other Candidas: Flat, round, yeast-like colonies. From time to time Nocardia can be isolated.
MICROBIOLOGICAL TEST
The following results were obtained in the performance of the medium from type cultures after incubation at a
temperature of 35 ± 2°C and observed after 18 - 24 hours.
Microorganisms
Growth
Colony Color
Enterobacter aerogenes ATCC 13048
Proteus mirabilis ATCC 14273
Salmonella typhimurium ATCC 14028
Escherichia coli ATCC 25922
Staphylococcus aureus ATCC 25923
Good
Good
Good
Good
Inhibited
Pink
Colorless
Colorless
Blue- black with green metallic sheen, black center
BIBLIOGRAPHY
Levine, J. Inf. Dis. 22:43. 1981. J. Bact. 45:471. 1943. Vogel, R.A. and Moses, R.M. Weld's Method for the Rapid Identification of
Candida albicans in Clinical Materials. Am. J. Clin. Path. 28:103-106. 1957.
STORAGE
25ºC
Once opened keep powdered medium closed to avoid hydration.
2ºC
2
LABORATORIOS CONDA, S.A.
www.condalab.com