Table 2 Phenotype and genotype of β-lactamases for the E. coli field isolate and mutants included in the study

E. coli

≤1/640

≤1/640

8/320

15/20

11/160

12/320

SHV-1(L138P)

TEM-20

RG E. coli-M1

12/160

1/40

-

-

-

-

SHV-1

RG E. coli-M2

28/40

14/40

-

-

-

-

L138P

RG E. coli-M3

11/160

1/160

-

-

-

-

P226S

RG E. coli-M4

28/20

12/2

-

-

-

-

L138P P226S