What’s new: The HonorHealth Microbiology Laboratory accreditation program (CAP) has updated requirements for antibiotic reporting.

• CAP requires that laboratories must document all breakpoints in use by MIC or disk diffusion methods.
• Additionally, there is a new requirement that states laboratories must use current breakpoints and implement new breakpoints within three years of the date of the official publication by FDA or CLSI.
• As such, the HonorHealth Microbiology Laboratory has completed an extensive review of our current antibiotic reporting and the revised CLSI and FDA breakpoints to determine necessary updates to be implemented.

Please see below for the changes in antibiotic reporting for Q1 2024:

• Gentamicin will no longer be reported on isolates of Pseudomonas aeruginosa. Gentamicin is now considered resistant and based on extensive data review; it was determined that doses necessary for effective treatment would be toxic. As such, it is no longer recommended and will no longer be reported on these isolates (CLSI M100 2023).
• Amikacin susceptibility for Pseudomonas aeruginosa will only be reported on isolates from urine cultures. As amikacin concentrates in the urine, clinical data shows that it is effective for treatment of UTI. It will no longer be reported on other specimen types, as Amikacin should only be considered for infections originating in the urinary tract (CLSI M100 2023).
• Updated Piperacillin/Tazobactam (P/T) breakpoints for Enterobacterales and Pseudomonas aeruginosa:

• Enterobacterales – new P/T breakpoints (CLSI M100 2022):
• Significant change: Lowered susceptible breakpoint and change from reporting “Intermediate” to “SDD.”
• Breakpoints for SDD are based on a dosage regimen of 4.5g administered every 6 h as a 3-h infusion or 4.5g administered every 8 h as a 4-h infusion.
• Pseudomonas aeruginosa – new P/T breakpoints (CLSI M100 2023):

• Significant change: Change “Intermediate” MIC Range based on PK-PD and clinical data that demonstrate very low probability of success treating aeruginosa with P/T MIC of 32-64 ug/mL and causing concerns that the previous “I” range implied increased exposures needed to treat an isolate within that range.
• Updated Oxacillin breakpoint for (Staphylococcus spp., not including aureus and S. lugdunensis (CLSI M100 2021; FDA 2022):

If you have any question or need additional information, please contact:

• Nikki Mai, PharmD, clinical pharmacy specialist infectious disease – [email protected]
• Michelle Dent, network manager infectious disease (laboratory) – [email protected]
• Neema Mafi, MD, infectious disease physician and Antibiotic Stewardship Committee Chair – [email protected]