EO Labs Colorex MRSA - 15mL - 10 x 90mm Plates

Colorex™ MRSA is a chromogenic medium for the selective isolation of Methicillin-Resistant Staphylococcus aureus (MRSA). The medium can be used for the routine screening of clinical specimens for MRSA from a variety of sampling sites such as the nose, throat and groin. The medium incorporates a nutritious peptone base medium and a number of selective agents to inhibit most Gram-negative and Gram-positive bacteria as well as yeasts and moulds. The chromogenic detection of specific enzyme activity leads to the formation of pink/mauve colonies indicating MRSA (including low level resistant and hetero-resistant strains) following incubation at 37°C for 18 to 24 hours. Other organisms, if present are indicated by blue or colourless colonies. Any presumptive isolates must be confirmed using serological and/or biochemical techniques available to the laboratory. The use of this chromogenic medium does not diminish the requirement for conventional antimicrobial susceptibility tests for the confirmation of methicillin resistance.

• Storage temperature: 2 to 8°C, store in the dark
• Appearance: firm gel
• Colour: straw
• Recommended incubation: aerobically at 35 to 37°C for 18 to 24 hours
• pH: 6.9 ± 0.2
• Plate size: 90mm
• Fill volume: 14 to 16mL

Limitations:

• Staphylococcus aureus strains (Borderline resistant S. aureus (BORSA)) that possess a low MIC to the selective agent present in the medium but are mecA negative may form colonies on the medium
• Low inoculum levels of some mecC MRSA isolates may not form typical colonies if the incubation temperature is above 36°C
• Some MRSA strains may form typical colonies surrounded by a halo, the formation of the halo serves no diagnostic function
• Certain methicillin-resistant coagulase-negative staphylococci (CNS) may produce characteristic colonies; in some cases, differentiation may be achieved by examination of the colour of these colonies, as they may be considerably darker in colour (bluish purple to a very dark pink/magenta)
• Certain bacterial species other than staphylococci may produce colonies with a characteristic colour, presumptive isolates must be confirmed using serological, biochemical, or mass spectroscopy (MALDI-TOF) tests, the use of this chromogenic medium does not diminish the requirement for conventional antimicrobial susceptibility tests for the confirmation of methicillin resistance
• Staphylococcus aureus NCTC 12493 will fail to grow on this medium.
• Definite identification as MRSA requires, in addition, a final identification as S. aureus