Post Traumatic Wound Infection: Testing for Methicillin Resistance

MRSA Screen

  • Perhaps the most efficient means for detecting methicillin-resistant staphylococci in clinical laboratories is the use of the agar dilution screening test.
  • Illustrated in the photograph is a Mueller-Hinton agar plate containing 6ug/ml of oxicillin, previously inoculated with a strain of Staphylococcus aureus. Oxacillin is used as a marker for methicillin resistance because it is more stable in the agar medium. Growth on this screening medium is presumptive for methicillin resistance.
  • Thus, in the presence of growth, as shown here, a follow-up MIC test must be performed to determine the exact level of resistance.

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