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Table 1 Minimum inhibitory concentrations (MICs) and fractional inhibitory concentration (FIC) index of blaIMP-1 or blaIMP-6 positive Enterobacteriaceae isolates

From: Bactericidal efficacy of meropenem in combination with cefmetazole against IMP-producing carbapenem-resistant Enterobacteriaceae

 

Isolates

 

MIC (μg/mL)

MEM MIC reduction

FIC index

Evaluation

MEM

CMZ

IMP-1 producing isolates

TUM10695

E. hormaechei

2

512

1/4, 1/8

0.27, 0.19

Synergy

TUM11051

E. hormaechei

8

2048

1/4, 1/4

0.50, 0.50

Synergy

TUM11052

E. hormaechei

8

1024

1/4, 1/4

0.28, 0.27

Synergy

TUM11134

E. hormaechei

2

1024

1/4, 1/4

0.31, 0.50

Synergy

TUM11259

E. coli

8

512

1/8, 1/8

0.25, 0.38

Synergy

TUM13773

E. coli

4

256

1/4, 1/8

0.50, 0.37

Synergy

TUM14683

E. coli

4

512

1/16, 1/8

0.19, 0.19

Synergy

TUM14697

E. coli

2

64

1/4, 1/8

0.38, 0.19

Synergy

TUM14759

E. coli

4

512

1/8, 1/4

0.25, 0.28

Synergy

TUM13774

K. pneumoniae

8

256

1/8, 1/8

0.25, 0.38

Synergy

TUM13775

K. pneumoniae

8

512

1/8, 1/8

0.25, 0.25

Synergy

TUM14366

K. pneumoniae

8

256

1/8, 1/4

0.25, 0.31

Synergy

TUM14380

K. pneumoniae

2

512

1/4, 1/4

0.50, 0.38

Synergy

IMP-6 producing isolates

E015

E. coli

16

256

1/8, 1/16

0.16, 0.13

Synergy

E020

E. coli

16

256

1/8, 1/16

0.13, 0.19

Synergy

E030

E. coli

32

512

1/16, 1/16

0.09, 0.08

Synergy

E038

E. coli

16

512

1/32, 1/16

0.05, 0.14

Synergy

E046

E. coli

32

1024

1/8, 1/8

0.14, 0.14

Synergy

E070

E. coli

16

256

1/32, 1/32

0.19, 0.06

Synergy

E109

E. coli

16

64

1/32, 1/32

0.28, 0.28

Synergy

E138

E. coli

64

1024

1/8, 1/8

0.19, 0.19

Synergy

E039

K. pneumoniae

32

256

1/16, 1/16

0.13, 0.13

Synergy

E045

K. pneumoniae

32

256

1/8, 1/16

0.16, 0.09

Synergy

E065

K. pneumoniae

32

256

1/32, 1/32

0.09, 0.06

Synergy

E085

K. pneumoniae

32

512

1/8, 1/8

0.19, 0.16

Synergy

E139

K. pneumoniae

32

1024

1/8, 1/4

0.25, 0.27

Synergy

  1. CMZ cefmetazole, MEM meropenem
  2. FIC index was measured in duplication. FIC index was calculated in following formula; FIC index = (MIC of MEM measured in combination with CMZ)/(MIC of MEM only) + (MIC of CMZ measured in combination with MEM)/(MIC of CMZ only). FIC index ≤ 0.5 was defined as synergy, > 0.5 to ≤ 4.0 as indifferent, and > 4.0 as antagonistic. MEM MIC fold-reduction by CMZ was calculated at the lowest FIC index