Mannitol Salt Agar

EMD Cat. No. 1.05404.0500
500 g


A modified version of the selective agar proposed by CHAPMAN (1945) for detecting pathogenic staphylococci in foodstuffs and other materials.

It complies with the recommendations in the United States Pharmacopeia 30.

Click here for information about harmonization of USP/EP chapters on Microbiological Examination of Non-sterile Products (formerly called Microbial Limits Test).






Mode of Action Preparation
Experimental Procedure and Evaluation Quality Control
Typical Composition (g/liter) Literature
Picture/Image


Mode of Action
 Only salt-tolerant microorganisms, including staphylococci, can grow on this medium, because of its high salt concentration. Degradation of mannitol to acid correlates, more or less, with the pathogenicity of Staph. aureus and thus serves as an indicator for this species.
Preparation
 Suspend 108 g/liter, autoclave (15 min at 121 °C), pour plates.
 pH: 7.4 ± 0.2 at 25 °C.
 The plates are clear and red.
Experimental Procedure and Evaluation
 Inoculate by spreading the sample on the surface of the medium. Inoculation should be massive on account of the strong inhibitory effect of the medium.
 Incubation: up to 3 days at 35 °C aerobically.
Further tests should be performed to confirm the diagnosis.
Appearance of Colonies
 		Microorganisms
Surrounded by bright yellow zones, abundant growth
 		Mannitol-positive:
 Staphylococcus aureus
No color change, growth is usually poorer
 		Mannitol-negative:
 Staphylococcus epidermis and others

Quality control (spiral plating method)

Test strains
 Inoculum
(cfu/ml)
 		Recovery rate
 %
 		color change
to yellow
Staphylococcus aureus ATCC 25923
 		10 - 100
 		≥30
 		+
Staphylococcus aureus ATCC 6538
 		10 - 100
 		≥30
 		+
Escherichia coli ATCC 8739
 		≥ 1-104
 		No growth
 		 
Staphylococcus epidermidis ATCC 12228
 		10 - 100
 		No spec
 		-
Staphylococcus epidermidis ATCC 14990
 		10 - 100
 		No spec
 		-
Proteus mirabilis ATCC 12453
 		10 - 100
 		No spec
 		-

Typical Composition (g/liter)
 Peptone from casein 5.0; Exzymatic digest of animal tissue 5.0; meat extract 1.0; sodium chloride 75.0; D(-)-mannitol 10.0; phenol red 0.025; agar-agar 12.0.
Literature

CHAPMAN, G.H.: The significance of sodium chloride in studies of staphylococci. - J. Bact., 50; 201-203 (1945).

United States Pharmacopeia 30

<61> Microbiological Examination of Non-sterile Products: Microbial Enumeration Tests (USP 30, page 89).
<62> Microbiological Examination of Non-sterile Products: Tests for Specified Microorganisms (USP 30, page 93).

European Pharmacopeia 6 (Ph. Eur)
2.6.12 Microbiological Harmonization of Non-sterile Products - Microbial Enumeration Test
2.6.12 Microbiological Harmonization of Non-sterile Products - Tests for Specified Microorganisms


Staphylosoccus aureus



© 2002 Merck KGaA, Darmstadt, Germany