Comparison of antimicrobial susceptibility interpretation among Enterobacteriaceae using CLSI and EUCAST breakpoints

To determine the difference in antimicrobial susceptibility of various antibiotics using the CLSI & EUCAST breakpoints.

In this non interventional, retrospective observational study, we reviewed minimum inhibitory concentrations (MIC) of various antibiotics routinely reported for Enterobacteriaceae clinical isolates, from an automated microbiology identification system (VITEK-2). These MICs were then analysed using both CLSI 2019 and EUCAST 2019 guidelines and classified as per the breakpoints into various categories.

The concordance rates of the antimicrobial susceptibility for various drugs ranged from 78.2% to 100% among two breakpoints. Perfect agreement with κ = 1 (p < 0.001) was observed for only three antimicrobials ceftriaxone, levofloxacin and trimethoprim-sulfamethoxazole. The changes in antimicrobial susceptibility interpretation for cefepime, ciprofloxacin, amoxicillin clavulanic acid was majorly in Intermediate category.

The change in interpretation of the susceptibility will lead to change in the usage of antibiotics especially due to recent change in definition of I by EUCAST. There is need of more studies in this aspect to ascertain clinical implication of change in antimicrobial susceptibility.