Description

Use and description:

Medium for primary differentiation and identification of Methycillin resistant Staphylococcus aureus strains. The medium uses different substrates to detect specific enzyme activities. Methycillin resistance coagulase negative staphylococcus (other than aureus) will grow with different colour (grey-blue or white).

 

Composition per litre:

Chromogenic mix…………………4.0 g

Agar…………………………………..13.0 g

Peptones……………………………22.0 g

Salt mix……………………………25.0 g

Meat extract…………………………3.0 g

Mineral supplement………..……1.8 g

 

Final pH of the ready to use medium: 6.3±0.2 at 25.0 °C

 

Medium preparation:

Add 68.8 grams of dehydrated culture medium to 1 litre of distilled water. Add 2 vials of Growth supplement. Mix thoroughly. Heat with intensive agitation and boil for 1 min. Autoclave for 15 minutes at 121°C. Cool to 45-50°C with very intensive mixing and add 1 vial of Selective supplement to every 500 ml medium. Pour into sterile petri dishes.

Quality specifications:

  1. The powder is homogeneous, free flowing and light beige.
  2. Ready to use medium: amber-coloured, clear-slightly opalescent agar

 

Microbiological response after 18-24 hours at 35-37 °C: 

OrganismGrowthColony / Colour
Staphylococcus aureus ATCC 43330Good1.5-2 mm deep magenta colonies with magenta halo
Staphylococcus epidermidis ATCC12228inhibitedVery small magenta colonies
Staphylococcus aureus ATCC 25923Inhibited
Staphylococcus saprophyticus ATCC 15305 Inhibited
Staphylococcus saprophyticus ATCC 15305 (without selective supplement)InhibitedBlue colonies
E.coli ATCC 25922Inhibited
Proteus mirabilis ATCC12453Inhibited

 

Storage:

Store the sealed bottle containing the dehydrated medium at 2 to 30°C. Once opened and recapped, place the container in a low humidity environment at the same storage temperature. Protect it from moisture and light. The dehydrated medium should be discarded if it is not free flowing or if the colour has changed from the original light beige colour.

500g wrapped pots