Reference Values

Reported as:

MRSA DNA Detected or Not Detected

Staph aureus DNA Detected or Not Detected

Limitations:

1. Testing with the MRSA/SA blood culture assay should be used as an adjunct to other methods available.

2. Erroneous test results might occur from improper specimen collection, failure to follow the recommended sample collection, handling and storage procedures, technical error, sample mix-up, or because the number of orgnaisms in the specimen is too low to be detected by the test. Careful compliance with the instructions in the package insert is necessary to avoid erroneous results.

3. MRSA/SA blood culture assay results may sometimes, be INVALID, ERROR, or NO RESULT, and require retesting that can lead to a delay in obtaining final results.

4. Target concentrations below the level of detection of the assay may be detected, but results may not be reproducible.

5. The MRSA/SA blood culture assay may generate a false negative MRSA result when testing borderline oxacillin resistant Staph aureus (BORSA). The mechanism of oxacillin resistance in these strains may be due to other factors (e.g. increased production of beta-lactamase rather than the presence of the mecA gene. BORSA with oxacillin MICs of 4-8ug/mL are considered borderline resistant but may be reported as MRSA negative by the MRSA/SA blood culture assay.

6. The MRSA/SA blood culture assay may generate a false negative MRSA result when testing modified SA (MOD-SA). The mechanism of oxacillin resistance in MOD-SA strains is due to other factors (e.g. changes in affinity of penicillin binding proteins of Oxacillin) rather than the presence of the mecA gene. MOD-SA with oxacillin MICs of 4-8 ug/mL are considered borderline resistant but, would be reported as MRSA negative by the MRSA/SA blood culture assay.

7. The MRSA/SA blood culture assay will generate a false negative MRSA result when testing a strain containing a mecA homologue known as mecC such as SA LGA251.

8. The MRSA/SA blood culture assay will generate a false positive MRSA result when testing a mixed infection blood culture specimen containing both Methicillin-resistant coagulase-negative Staphyloccus (MRCNS) and Methicillin-susceptible SA.