**2.4 Antimicrobial susceptibility testing**

All identified isolates of *E. coli* were treated for susceptibility testing against amoxicillin (25 μg), amoxicillin-clavulanic acid (20/10 μg), ceftriaxone (30 μg), cefotaxime (30 μg), cefepime (30 μg), cefixime (10 μg), piperacillin (75 μg), piperacillin-tazobactam (100 + 10 μg), imipenem (10 μg), and aztreonam (30 μg) (Bio-Rad, France) following disk diffusion method on Mueller-Hinton Agar (Liofilchem, Italy). Results were interpreted based on the European Committee of Antimicrobial Susceptibility Testing (EUCAST) guidelines [21]. These isolates, which were not susceptible (either resistant or intermediate) to three or more antibiotics classes, were considered as MDR [22].
