MacConkey Agar

(without salt)

LAB 2

Description

A medium first introduced by MacConkey in 1905 for the isolation and differentiation of lactose and non lactose fermenting enteric bacteria. The medium has since been modified to improve the recovery of staphylococci and enterococci, it is used for culturing a wide range of clinical material and has applications in food, water and dairy bacteriology.

Method for reconstitution

Weigh 48.5 grams of powder, disperse in 1 litre of deionised water. Allow to soak for 10 minutes, swirl to mix then sterilise by autoclaving for 15 minutes at 121˚C. Cool to 47˚C and mix well before pouring plates. Prior to inoculation, dry the surface of the agar by partial exposure at 37˚C.

Appearance: Pink/red, clear.

pH: 7.4 ± 0.2

Minimum Q.C. organisms: E. coli NCIMB 50034

S. aureus NCIMB 50080

Storage of Prepared Medium: Plates - up to 7 days at 2-8˚C in the dark.

Inoculation: Surface inoculation, streaking for single colonies.

Incubation: 37˚C aerobically for 24 hours.

Growth Characteristics

colour

organism

CV.E.G.       Pink-Deep Red

References

MacConkey, A.T.  (1905) Lactose-fermenting  bacteria in  faeces. J.Hyg. (Camb), 5: 333-379.