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Table 4 Characteristics of isolates with false mCIM/eCIM results

From: Combination of modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) for phenotypic detection of carbapenemase-producing Enterobacteriaceae

Isolatea

Carbapenemase

MIC (μg/ml)

Disc zone (mm)

Phenotypic detection

IPM

ETP

MEM

IPM

ETP

MEM

DOP

mCIM

eCIM

MHT

mCIM/eCIMa

False-positive

 E. coli 514

blaOXA-48

8

≥ 8

≥ 16

16

12

15

16

6

23

–

+

False-negative

 K. pneumoniae 456

blaIMP-8

0.5

2

≤0.25

22

18

25

25

19

20

–

–

 E. coli 488

blaOXA-48/blaNDM-5

≥ 16

≥ 8

8

6

6

6

6

6

6

+

–

 E. coli 492

blaOXA-48/blaNDM-5

≥ 16

≥ 8

≥ 16

6

6

6

6

6

6

+

–

  1. aAn isolate is positive for metallo-carbapenemase production when the eCIM zone size increases by ≥5 mm compared to the zone size observed for the mCIM and is considered negative for a metallo-carbapenemase if the increase in zone size is < 4 mm
  2. IPM imipenem, ETP ertapenem, MEM meropenem