MacCONKEY Agar

EMD Cat. No. 1.05465.0500/5000
500 g, 5 kg


Selective agar for the isolation of Salmonella, Shigella and coliform bacteria from faeces, urine, foodstuffs, waste water etc. according to MacCONKEY (1950).

The composition of this medium largely complies with the United States Pharmacopeia 30 and the European Pharmacopeia 6.

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


ChemDat®

Mode of Action
 Bile salts and crystal violet largely inhibit the growth of the Gram-positive microbial flora. Lactose and the pH indicator neutral red are used to detect lactose degradation.

Typical Composition (g/liter):

Peptone from Gelatin 17.0; Peptone from Casein 1.5; Peptone from Meat 1.5; Sodium Chloride 5.0; Lactose 10.0; Bile Salt Mixture 1.5; Neutral Red 0.03; Crystal Violet 0.001; Agar-agar 13.5.

Preparation
 Suspend 50 g/liter, autoclave (15 min at 121 °C), pour plates.
 pH: 7.1 ± 0.2 at 25 °C.
 The plates are clear and red-brown to dark red.
Experimental Procedure and Evaluation
 Inoculate by spreading the sample material on the surface of the plates.
 Incubation: 18-24 hours at 35 °C aerobically.
Lactose-negative colonies are colorless; lactose-positive colonies are red and surrounded by a turbid zone which is due to the precipitation of bile acids as a result of pH decrease.
Appearance of Colonies
 		Microorganisms
colorless, translucent
 		Salmonella, Shigella and others
Large, red, surrounded by turbid zone
 		Escherichia coli
Large, pink, mucoid
 		Enterobacter, Klebsiella
Very small, opaque, isolated colonies
 		Enterococci, Staphylococci and others

Quality control (spiral plating method)

Test strains
 Inoculum
 (cfu/ml)
 		Recovery rate (%)
 		color
of
 Precipitate



colony
 		medium
Escherichia coli ATCC 8739 *
 		10 - 100
 		≥= 30
 		red
 		red
 		+
Salmonella typhimurium ATCC 14028
 		10 - 100
 		≥= 30
 		colorless
 		yellowish
Salmonella dublin ATCC 15480
 		10 - 100
 		≥= 30
 		colorless
 		yellowish
Shigella sonnei ATCC 11060
 		10 - 100
 		≥= 30
 		colorless
 		yellowish
Proteus mirabilis ATCC 29906
 		10 - 100
 		≥= 30
 		colorless
 		yellowish
Bacillus cereus ATCC 11778
 		> 105
 		No growth


Staphylococcus aureus ATCC 6538
 		> 105
 		No growth


Enterococcus hirae ATCC 8043
 		> 105
 		No growth


Enterococcus faecalis ATCC 19433
 		> 105
 		No growth


Enterococcus faecalis ATCC 28212
 		> 105
 		No growth


* (at 37°C and 43-45°C)





Typical Composition (g/liter)
 Peptone from casein 17.0; peptone from meat 3.0; sodium chloride 5.0; lactose 10.0; bile salt mixture 1.5; neutral red 0.03; crystal violet 0.001; agar-agar 13.5.
Literature

MacCONKEY, A.: Lactose-fermenting bacteria in faeces. - J. Hyg., 8; 333-379 (1905).


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




© 2002 Merck KGaA, Darmstadt, Germany