Methicillin (oxacillin)-resistant Staphylococcus aureus: Oxacillin Salt Agar

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 180 CE courses, most popular		$109Add to cart
Pick Your Courses
Up to 8 CE hours		$55Add to cart
Individual course$25Add to cart
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Case Studies in Clinical Microbiology. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Case Studies in Clinical Microbiology (online CE course)
Methicillin (oxacillin)-resistant Staphylococcus aureus: Oxacillin Salt Agar

  • One method for detecting methicillin (oxacillin)-resistant Staphylococcus aureus in clinical laboratories is the use of the oxacillin salt agar. This method is used to detect mecA-mediated resistance using oxacillin salt agar for S. aureus only (CLSI, 2021).
  • Illustrated in the image is a Mueller-Hinton agar plate containing 6 μg/mL of oxacillin and 4% NaCl, 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 (oxacillin) resistance.
  • Thus, in the presence of growth, as shown here, a follow-up minimum inhibitory concentration (MIC) test must be performed to determine the exact level of resistance.