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Material Safety Data Sheet

Organisms

Organisms this product works with:

Dehydrated Culture Media

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

 

* Adjusted as required to meet performance standards

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

* This organism is available as a Culti-Loop®

Reference
1. McGeachie J. and Kennedy A. C. (1963) J. Clin. Path. 16. 32-38.

 
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