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. 2020 Jan 27;64(2):e01495-19. doi: 10.1128/AAC.01495-19

TABLE 1.

Colistin reference broth microdilution MIC distributions for U.S. isolates (128,573; SENTRY Program, 2011 to 2017)a

Organism(s)
(no. tested)
% at indicated MIC (mg/liter)
MIC50/MIC90
≤0.5 1 2 4 ≥8
Enterobacteriaceae (96,847) 74.9 3.9b 0.6 0.4 20.3 ≤0.5/>4
    WT group (79,474)c 91.5 4.5b 0.6 0.3 3.1 ≤0.5/≤0.5
    IR group (17,373)d 0.8 0.8b 0.3 0.1 98.0 >4/>4
P. aeruginosa (23,685) 20.0 50.8 28.6b 0.5 0.1 1/2
Acinetobacter spp. (6,796) 44.5 37.9 12.1b 2.2 3.4 1/2

aThe vertical line indicates the proposed breakpoint (≤2 mg/liter) for susceptibility.

bPerceived limit of WT population (ECOFF).

cWT, wild-type strain MICs, generally without resistance mechanisms (E. coli, Klebsiella spp., Enterobacter spp., Citrobacter spp.).

dIR, intrinsic resistance in genera/species (Proteus mirabilis, indole-positive Proteae, and Serratia marcescens).