LETHEEN AGAR MODIFIED
CAT Nº: 1111
For the microbiological analysis of cosmetics
FORMULA IN g/l
Casein Peptone
10.0
Yeast Extract
2.0
Meat Peptone
10.0
Glucose
1.0
Polisorbate 80
7.0
Lecithin
1.0
Sodium Chloride
5.0
Sodium Bisulfite
0.1
Beef Extract
3.0
Bacteriological Agar
20.0
Final pH 7.2 ± 0.2 at 25ºC
PREPARATION
Suspend 59.1 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 50ºC, mix
well and dispense into plates. The prepared medium should be stored at 8-15°C. The color is amber, slightly opalescent.
The dehydrated medium should be homogeneous, free-flowing and beige in color. If there are any physical changes,
discard the medium.
USES
LETHEEN AGAR MODIFIED is based on the formula described in the FDA Bacteriological Analytical Manual, is a
modification of Letheen Broth Base. It is highly nutritious and recommended for use in the microbiological testing of
cosmetics. It can be used to inactivate quarternary ammonium compounds and other preservatives when establishing
the number of bacteria present in cosmetics and other materials.
Beef Extract, Casein peptone and Meat peptone provide nitrogen, vitamins, minerals and amino acids essential for
growth. Yeast extract is the source of vitamins, particularly of the B-group. Glucose is the fermentable carbohydrate
providing carbon and energy. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Lecithin,
Polisorbate 80 and Sodium bisulfite neutralize quaternary ammonium compounds and partially neutralize the
preservative system commonly found in cosmetics. Bacteriological Agar is the solidifying agent.
The medium is also used for microbiological samples from surfaces that have been treated with disinfectants.
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 alter 18-24 hours.
Microorganisms
Staphylococcus aureus ATCC 25923
Staphylococcus epidermidis ATCC 12228
Streptococcus pneumoniae ATCC 6306
Streptococcus pyogenes ATCC 19615
Growth
Good
Good
Good
Good
Inoculum
cfu/ml
102-103
102-103
102-103
102-103
Recovery
Rate %
≥70
≥70
≥70
≥70
BIBLIOGRAPHY
1
LABORATORIOS CONDA, S.A.
www.condalab.com
FIJA Bacteriological Analytical Manual (BMA] 1995. Microbiological Methods for cosmetics, Letheen Agar (modified]. Letheen Broth
(modified))
STORAGE
25ºC
Once opened keep powdered medium closed to avoid hydration.
2ºC
2
LABORATORIOS CONDA, S.A.
www.condalab.com