Approved Hospital Formulary
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Approved Hospital Formulary
03/10/20 jm New fluoroquinolone Susceptibility Breakpoints for Enterobacteriaceae
March 10, 2020
From: "Justin Muklewicz" <justin.muklewicz@hhsys.org>
To: "Pharmacists" <grp_allpharm@hhsys.org>
Sent: Tuesday, March 10, 2020 6:25:43 AM
Subject: New fluoroquinolone Susceptibility Breakpoints for Enterobacteriaceae
Good morning team,
I would like to announce a new change to microbiology susceptibility reports that you will see during the next few months. This change will affect all fluoroquinolone susceptibilities for Enterobacteriaceae only (e.g., E. coli, Klebsiella pneumoniae,Enterobacter spp., etc...). This change affects all patients regardless of age.
What is changing?
- There will be a disclaimer at the bottom of certain microbiology reports stating that fluoroquinolone susceptibilities for Enterobaceriaceae "do not represent the lowered 2019 CLSI breakpoints". The Clinical & Laboratory Standards Institute (CLSI) is an international organization that provides standardized high-quality laboratory references, including yearly updates for in vitro antimicrobial susceptibility breakpoints (gold standard). Susceptibility panels are frequently out of date with CLSI because of the strict FDA requirements for these panels which causes delays.
Why is this change occurring?
- The 2019 CLSI update decreased the fluoroquinolone susceptibility breakpoint for Enterobaceriaceae by 2 standard dilutions (levofloxacin breakpoint was 2 μg/mL, now 0.5 μg/mL). The reason for this change was due to new literature showing that previously set breakpoints were too high to detect certain certain types of resistance. (in other words, resistance was occurring despite microbiology reports reporting susceptibility)
- The current susceptibility panel utilized at Huntsville Hospital does not permit us to detect the new breakpoint to determine if the organism is susceptible (ie. the panel does not test concentrations of levofloxacin at or below 0.5 μg/mL)
How do I interpret this change?
- With our current susceptibility panel, if an organism belonging to the Enterobacteriaceae family is reported to be susceptible (S) to a fluoroquinolone, it is unknown if it is susceptible, intermediate, or resistant according to the 2019 CLSI breakpoints.
- The proportion of Enterobaceriaceae isolates susceptible to fluoroquinolones will effectively decrease to an unknown degree.
Clinical impact: the risk vs benefit of utilizing a fluoroquinolone must be determined on a patient-by-patient basis.
- Uncomplicated UTI: likely does not pose a significant risk for treatment failure because fluoroquinolone concentrations in the urine may overcome certain types of resistance.
- Other sources: risk vs. benefit of continuing a fluoroquinolone should be taken in consideration with the patient's clinical status and whether or not the patient is clinically improving.
How long will this disclaimer be in effect?
- The ID Subcommittee has approved a new susceptibility panel that is up-to-date with the 2019 CLSI recommendations for these fluoroquinolone susceptibility breakpoints. This change to the new panel will allow us to determine if these isolates are susceptible to fluoroquinolones. The change is anticipated to occur mid-2020 and staff will be notified of this change.
For any questions, including treatment recommendations in specific patients, please do not hesitate to contact Jonathan or myself (x50286). Thank you.