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. 2020 Feb 24;58(3):e01555-19. doi: 10.1128/JCM.01555-19

TABLE 1.

Results summarizing the assays of the colistin agar-spot screening test (CAST) and EDTA colistin agar-spot screening test (eCAST)

Isolate No. of isolates MIC50 and MIC range (mg/liter) CASTd eCASTd
COLR mcr positivea 49 8 (4–32) G NG
COLR mcr negativeb 9 16 (16–64) G G
COLSc 34 0.5 (0.25–2) NG NG
a

The 49 MCR-producing isolates included 48 E. coli (45 mcr-1, 1 mcr-2, 1 mcr-4, and 1 mcr-5) and 1 K. pneumoniae (mcr-1); 4 out of 46 mcr-1-positive strains were carbapenemase producers (2 NDM-1 and 2 OXA-163).

b

The nine colistin-resistant isolates included one S. marcescens and eight K. pneumoniae; six of them were carbapenemase producers (five KPC-2 and one NDM-1). Five out of eight K. pneumoniae isolates showed the ΔmgrB locus.

c

The colistin-susceptible isolates included 26 E. coli and 8 K. pneumoniae (all of them mcr negative); 10 out of 34 were carbapenemase producers (9 NDM-1 and 1 OXA-181).

d

G, growth; NG, no growth.