MIC Breakpoint Change: FAQs and Concerns

1. MIC Breakpoint Change: FAQs and Concerns 1. What changed? Primarily lowering of breakpoints for beta-lactams for gram-negative bacteria 2. Why did this change? (1) To enhance detection of known resistance among Enterobactericeae; (2) to eliminate the need for ESBL testing; (3) to allow antibiotic choices based on MICs alone 3. What is the impact? (1) See Tables; (2) potentially less work for Micro lab; (3) quicker TAT for MIC results; (4) will provide results that are more consistent with international results (i.e., EUCAST); (5) will allow us to keep up with automated Vitek changes annually 4. What are the concerns? a. Lowering the breakpoints will result in both empiric and directed use of broader spectrum antibiotics without much clinical benefit (except cefazolin use for urine Enterobactericeae)—CON for switching b. Many academic peers have either not made the changes or have modified how they report the changes—CON c. Using old breakpoints keeps us for implementing change orders including those for new antibiotics—PRO for switching d. Many peers and other NM System hospitals have changed—PRO e. The switch could allow detection and feedback on site-specific (i.e. urine/non-urine) use of beta-lactams—PRO f. Apart from seeing more R isolates, we will see more Intermediate isolates—we will need to educate on this, but realistically, this will probably push use to broader agents—CON g. We don’t currently test cefazolin MICs below 4. A new methodology would have to be implemented in the lab to test lower breakpoints—Neither for clinicians/CON for lab

2. MIC Breakpoint Change: FAQs and Concerns 5. Realistically, what are we potentially talking about? Increases in use of our broader agents for Enterobacteriaceae with skew from cefazolin, ceftriaxone to ceftazidime/cefepime/aztreonam/carbapenems/avycaz/zerbaxa/vabomere More “Intermediate” Pseudomonas with zosyn MIC 32 may skew use to alternatives More “Intermediate” Acinetobacter to carbapenems may increase use of polymyxins, minocycline/tigecycline More “Intermediate” GN isolates across the board Push to get rid of ESBL testing 6. What is proposed to alleviate the concerns? Educational campaign re: changes ASP to perform DUE at 3 months after adopting new CLSI guidelines Increased focus by ASP to intervene to identify narrowest agent (interventions targeted to problem areas) Annual review of empiric guidelines to choose preferred agent i. Posting on Antibiotic Resources ii. Widespread availability of Antibiotic Resources on Internet ASP Website e. Increased ASP focus on de-escalation and stopping antibiotics in the absence of clinical isolate to guide treatment

3. Estimated Impact of MIC Changes: Extrapolated from CY 2017 Data (Vitek 2)

4. Will we use too many broad-spectrum antibiotics? Look at R breakpoint…

6. For our MDROs, will we use too many narrow-spectrum antibiotics? Look at S breakpoint…

8. The Proposed Changes • Adopt the 2018 CLSI Breakpoints with the following changes: 1. Continue to perform ESBL testing as we do now. • Always flip aztreonam, the 3rd generation cephalosporins and cefepime to R but report the actual MIC values. 2. Cefazolin testing: • Cefazolin will be reported as susceptible up to an MIC value of 16 mcg/ml for urine isolates of E. coli, K. pneumoniae and P. mirabilis. • The following comment will be added to the susceptibility report for urinary isolates: • This susceptibility result applies to the treatment of patients with uncomplicated urinary tract infections and is based on a dosage regimen of 1g every 12 hours. Breakpoints and susceptibility results for non-urine isolates differ. • Non-urine isolates will be considered susceptible at an MIC of <=4 (not 2) and resistant at an MIC of 8 or greater.

9. 2019 CLSI Updates