Updates to antimicrobial susceptibility testing
On Monday, Dec. 11, we implemented updates to antimicrobial susceptibility testing (AST). These updates include changing breakpoints for several antimicrobial agents for Enterobacterales and Pseudomonas aeruginosa. In addition to breakpoint changes, we changed what antimicrobial agents are reported on Pseudomonas aeruginosa. These changes affect all sites on the Front Range. All updates made to the AST testing are derived from the 2023 CLSI M100 33rd edition.
Reporting changes for Pseudomonas aeruginosa:
Gentamicin is no longer a recommended agent for Pseudomonas aeruginosa for any source and will no longer be reported.
Amikacin is only a recommended agent for Pseudomonas aeruginosa in urine tract sources and will only be reported on urine sources.
The following comment will be added to the Pseudomonas aeruginosa identification to reflect these changes: “For Pseudomonas aeruginosa, tobramycin is the aminoglycoside of choice if indicated, amikacin is only recommended for urine sources and gentamicin is no longer recommended.”
Updated breakpoints:
These breakpoints are being updated to align with the 2023 CLSI guidelines. At this time only a few of the 2023 CLSI Breakpoint changes are being implemented (see note below for breakpoints not being updated) in the report. In addition to the 2023 CLSI updates, breakpoints for Cefuroxime will be updated to the oral breakpoints to better align with the way the agent is administered.
Updated breakpoints For LAB MIC Method (testing performed on the BD Phoenix):
*Note regarding 2023 CLSI breakpoints not being updated: Due to testing limitations on our Phoenix Susceptibility Panel, we will not be able to update the breakpoints for Amikacin for Enterobacterales and Tobramycin for Pseudomonas aeruginosa at this time. The new breakpoints for these two drug/organism combos are listed below for your reference. For any questions regarding the use of these agents, please contact your local ID Pharmacist or Infectious Disease Provider.
Updated breakpoints for LAB KB Method (testing performed by Kirby Bauer):
For any questions regarding these updates, please contact your local ID Pharmacist or the Saint Joseph Microbiology Laboratory.