M124-2

Nares swab: methicillin-resistant Staphylococcus aureus (MRSA) – Shipped February 2013

HISTORY

The challenge was sent to category A and B laboratories. The sample was a simulated nares swab obtained as a MRSA admission screen from a 58 year old patient .

Participants were expected to isolate and report MRSA and notify Infection Control (IC).

MAIN EDUCATIONAL POINTS from M124-2

  1. Approximately 1% of MRSA are being misclassified as methicillin-susceptible S. aureus (MSSA) based on routinely used phenotypic tests.
  2. Heteroresistance is proposed as the reason for the difference between phenotype and genotype for oxacillin-susceptible MRSA (OS-MRSA).

Full critique (PDF)

Posted in Clinical Bacteriology Results, critiques