Throat swab: group A Streptococcus – Shipped August 15, 2016


A simulated throat swab collected from a 45 year old diabetic patient allergic to penicillin was sent to category A, B, and C laboratories.

Participants were expected to report group A Streptococcus (GAS) or Streptococcus pyogenes and perform antimicrobial susceptibility testing.

An additional swab to run a rapid antigen detection test (RADT) was included in this challenge.


  1. Isolates of GAS are universally susceptible to penicillin (and other β-lactams approved for the treatment of β-hemolytic streptococcal infections) and routine antimicrobial susceptibility testing of penicillin need not be performed.
  2. Penicillin allergic patients with pharyngitis who grow GAS from a throat swab require antimicrobial susceptibility testing to be performed for erythromycin and clindamycin, including a test for inducible clindamycin resistance (D-test), as isolates of GAS in Canada can be resistant to both erythromycin (and other macrolides) and clindamycin.

Full critique (PDF)

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