Urine: >100 x 10^6 cfu/L Aerococcus urinae. Shipped August 12, 2019. FINAL RESULT


A simulated midstream urine collected from 62-year-old female with dysuria was sent to category A and C laboratories.

Participants were expected to isolate and report Aerococcus urinae.


  1. Aerococcus urinae is infrequently isolated from urine cultures.
  2. Although it was previously thought to be a urinary contaminant lacking clinical significance, A. urinae has been linked to cystitis as well as complicated urinary tract infections (UTIs), especially in elderly males and immunocompromised patients.
  3. Although breakpoints for Aerococcus species have been added to the 2016 edition of the Clinical and Laboratory Standards Institute (CLSI) M45 – Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria, they are not based on a large number of isolates and should be applied with caution.
  4. Due to the infrequent isolation of A. urinae, clinicians likely benefit from guidance regarding its susceptibility to narrow-spectrum antibiotics such as penicillin, amoxicillin, and nitrofurantoin.

Full critique (PDF)

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