N °401670-rev.1 BE –1 02/2011 page 1/ 1
Powdered and ready to use selective and differential medium for the isolation and differentiation of Enterobacteriaceae
Mac Conkey Agar: E.coli
(pink colonies with red halo)
Pseudomonas aeruginosa (green colonies)
T YPICAL FORMULA (g/l)
Pancreatic Digest of Gelatin 17.000
Peptones (meat and casein) 3.000
Lactose monohydrate
Bile Salts n. 3
Sodium Chloride
Neutral Red
Crystal Violet
Agar
10.000
1.500
5.000
0.030
0.001
13.500
D IRECTIONS FOR POWDERED MEDIUM
Suspend 50g in 1000ml of cold distilled water, heat to boiling and sterilize by autoclaving at 121ºC for
15 minutes. Dry the surface of the medium before inoculation.
Final pH 7.1 ± 0.2
D IRECTIONS FOR READY TO USE MEDIUM IN FLASKS
Dissolve the contents of the bottle in a temperature controlled water batch (100°C). Cool to 45-50°C, mix well and distribute into sterile Petri dishes
Final pH 7.1 ± 0.2
D ESCRIPTION
MacConkey Agar is a selective and differential medium for the detection of Enterobacteriaceae and for the differentiation of lactose-fermenting strains from non-lactose-fermenters. The formulation complies with EP and USP recommendations for the detection of E.coli
in non-sterile pharmaceutical products.
The original MacConkey medium has been modified in the present preparation: the agar content is lower, 5g/l of sodium chloride has been added, the concentration of bile salts and neutral red has been modified. These modifications support excellent growth of most strains of Salmonella and Shigella , and permit better differentiation of these pathogens from coliform bacteria. The selective action of
MacConkey Agar is due to the presence of bile salts no. 3, which inhibit the growth of Gram-positive bacteria. This inhibitory action is enhanced by the addition of crystal violet. The fermentation of lactose by coliforms causes acidification of the medium, with the consequent precipitation of the bile salts and absorption of the neutral red. The coliform bacteria grow with brick red colonies surrounded by a precipitation zone. Lactose non-fermenters starins (Salmonella spp. and Shigella spp.) develop transparent, colourless colonies with no precipitation zone. The swarming of the Proteus spp. is partially controlled on MacConkey Agar by using selected raw materials.
Biolife Italiana S.r.l. Viale Monza 272, 20128 Milan, Italy. Tel. n° ++39 (0)2 25 209 1, Fax n° ++39 (0)2 25 76 428
E-mail: biolife@masciabrunelli.it ; Web: www.biolifeit.com

N °401670-rev.1 BE –1 02/2011 page 2/ 2
T ECHNIQUE
Transfer about 20ml of the medium to sterile Petri dishes, 9cm in diameter. Leave the medium to dry with the dish cover half on. It is important that the surface of the medium is thoroughly dry before use.
Inoculate the plates by surface streaking the medium with the material to be examined, incubate at
37 º C for 16-18 hours. Examine the medium for typical colonies. Colonies of lactose fermenting bacteria appear brick red to dark pink in colour and may be surrounded by a zone of bile precipitation.
Non lactose fermenting colonies are colourless. A longer incubation period alters the growth characteristics of the microorganisms. For the isolation and detection of pathogenic enteric bacteria the use of MacConkey Agar together with other more selective media, such as SS Agar and Bismuth
Sulphite Agar, is recommended.
User quality assurance (37°C - 24hrs)
Productivity control
E.coli
ATCC 25922*: growth, pink colonies
P.mirabilis ATCC 12453*: growth, colourless colonies, and inhibition of swarming
S.typhimurium ATCC 14028* : growth, colourless colonies
Selectivity control
E faecalis ATCC 29212*: inhibited
*NCCLS M22-A3 recommended strains.
S TORAGE
Dehydrated medium: 10-30°C
User prepared plates: 15 days at 2-8°C
Ready to use plates and flasks: 2-8°C
R EFERENCES
• European Pharmacopoeia, 7rd ed.
• FDA (1995) Bacteriological Analytical Manual, 8th ed. Revision A, 1998. Published by AOAC
International.
NCCLS document M22-A3, 2004. Quality Control of Commercially Prepared Microbiological Media: Approved
Standard - Third Edition. Vol. 24 No.19
Packaging
4016702
4016704
541670
5116702
5116703
MacConkey Agar, 500 g (10 l)
MacConkey Agar, 5 kg (100 l)
MacConkey Agar, 20 ready to use plates
MacConkey Agar, 6 x 100 ml ready to use flasks
MacConkey Agar, 6 x 200 ml ready to use flasks
Biolife Italiana S.r.l. Viale Monza 272, 20128 Milan, Italy. Tel. n° ++39 (0)2 25 209 1, Fax n° ++39 (0)2 25 76 428
E-mail: biolife@masciabrunelli.it ; Web: www.biolifeit.com