Part of Thermo Fisher Scientific
Organisms this product works with:
Other products used in the isolation of Shigellae:
MACCONKEY AGAR NO.2
Code: CM0109
A modification of MacConkey Agar No.3 containing Oxoid Bile Salts No.2 for the recognition of enterococci.
Typical Formula* | gm/litre |
Peptone | 20.0 |
Lactose | 10.0 |
Bile salts No.2 | 1.5 |
Sodium chloride | 5.0 |
Neutral red | 0.05 |
Crystal violet | 0.001 |
Agar | 15.0 |
pH 7.2 ± 0.2 @ 25°C |
|
Directions
Suspend 51.5g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.
Description
MacConkey Agar No.2 is a modification of the original MacConkey solid medium and is especially useful for the recognition of enterococci, in the presence of coliforms and non-lactose fermenters from water, sewage, food products, etc.
On this medium enterococci appear as small intensely red colonies with a pale periphery about 1mm in diameter. These organisms are frequently sought as an index of faecal pollution. Non-lactose fermenters are colourless. Bile tolerant Gram positive cocci, such as staphylococci and non-faecal streptococci, are completely inhibited.
McGeachie & Kennedy 1 employed Oxoid MacConkey Agar No.2 in a simplified method for counting the bacteria in urine. Using a bacteriological loop (delivering a known volume) they streaked well mixed uncentrifuged urine directly on to a blood agar and a MacConkey Agar plate - and spread the urine in a 1cm wide strip across one edge of the plate using 20 strokes. With a second sterile loop they spread a 1cm wide portion to form a second strip at right angles to the first. This was repeated to give a square pattern of four 1cm wide strips around the edge of the plate. After incubation, growth was noted as +, + +, + + +, or + + + + depending on whether 1, 2, 3 or 4 sides of the square showed colonies. The approximate estimate obtained agreed well with a more complicated pour-plate method and the simplified method was recommended for routine use.
Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C.
Appearance
Dehydrated medium: Pink coloured, free-flowing powder
Prepared medium: Dark red coloured gel
Quality control
Positive control: | Expected results |
Enterococcus faecalis ATCC® 29212 * | Good growth; pink coloured colonies with red centres. |
Negative control: | |
Uninoculated medium. | No change |
Reference
1. McGeachie J. and Kennedy A. C. (1963) J. Clin. Path. 16. 32-38.