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Contrast MRSA Broth

Code: EB1225

Oxoid Contrast MRSA Broth, EB1225, is an improved screening medium for the detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from clinical samples.

* Adjusted as required to meet performance standards

Description

Simplicity and speed are important factors when screening for MRSA. Reliable results are necessary for an effective infection control process. This will enable patients colonised with MRSA to be treated appropriately and in a timely manner.

Contrast™ MRSA Broth is a quick and easy screening test as an alternative to direct plating. The broth offers the huge benefit that more than one sample per patient can be inoculated into one broth.

Contrast MRSA Broth contains the same antibiotic marker used in Brilliance™ MRSA Agar to select for MRSA strains. Other antibiotics and inhibitory agents are present to inhibit non-MRSA and Gram-negative organisms. The broth contains an indicator dye, phenol red, and two sugars (mannitol and trehalose) which are fermented by MRSA strains. This causes a decrease in the pH of the broth, resulting in a colour change from red to orange/yellow, indicating a positive result.

The improved broth contains a low level of nalidixic acid, which has activity against both Gram-positive and Gram-negative bacteria. The concentration is optimized for maximum activity against non-target organisms without compromising growth of methicillin-resistant S. aureus, including ciprofloxicin-sensitive strains.

Contrast MRSA Broth can be inoculated from screening swabs taken from hospital patients or staff, according to local guidelines. Multiple swabs (maximum 4) from the same patient can be pooled into a single broth.

Technique

The broth should be allowed to warm to room temperature before inoculation. After inoculating the swabs into the broth incubate for 18–24 hours at 37ºC. There is no need to incubate beyond 24 hours. A colour change from red to yellow/orange indicates a presumptive positive result for MRSA. Negatives stay red. The results are presumptive; positive results should be confirmed. Brilliance MRSA 2 Agar (PO1210 /PO5310) and PBP2′ (DR0900) can be used to confirm MRSA.

For further instructions on the use and interpretation of Contrast MRSA Broth, simply download the data sheet in PDF format.

Storage conditions and shelf life

Contrast MRSA Broth should be stored in the original packaging at the temperature stated on the pack or product specification, and protected from direct light. When stored as directed, the unopened product will remain stable until the expiry date on the label. Once brought to room temperature, the product should be used within 12 hours.

Appearance

Prepared medium: red, liquid medium in universals

Quality Control

Precautions

Contrast MRSA Broth is for in vitro diagnostic use only, by trained individuals. Do not use beyond the expiry date given on the label, or if the product shows any sign of deterioration.

Sterilise specimens, equipment and media properly after use.

Limitations

Streaking from Contrast MRSA broth onto Brilliance MRSA 2 agar can result in an elevated incidence of false positive results, and confirmation of mecA carriage using the Oxoid PBP2′ (DR0900) test or other recognised method is recommended.

Refs

1. Perry, J.D., Davies, A., Butterworth, L.A., Hopley, A.L.J., Nicholson, A. and Gould, F.K. ,”Development and evaluation of a chromogenic agar medium for methicillin-resistant Staphylococcus aureus,” J. Clin. Micro. (2004) 42 (10), 4519-4523.
2. Davies, A., Perry, J.D., Butterworth, L. A., Nicholson, A. and Gould, F. K, “An evaluation of MRSA ID: a new chromogenic medium for the isolation and identification of methicillin-resistant Staphylococcus aureus,” Poster by Microbiology Dept, Freeman Hospital, Newcastle-Upon Tyne.

ATCC® is a registered trademark of American Type Culture Collection