Antimicrobial Susceptibility Testing Protocol

The antimicrobial susceptibility testing was done following a previously reported method [26 (link)]. Briefly, the pure colonies obtained from blood agar were resuspended in bacterial suspensions, and were made depositing two or three medium-sized colonies (2 to 3 mm) in BBL Crystal Inoculum Broth (Becton Dickinson; Franklin Lakes, NJ, USA). The obtained inoculum was adjusted while using a Mac Farland 0.5 reading (Expected CFU/mL 1.5 × 108), and cultured in Müeller Hinton 150 × 15 mm² media BD BBL (Becton Dickinson Franklin Lakes, NJ, USA). The antibiotic discs were applied with the Sensi-Disc Designer Dispenser System. The antibiotics panel was conformed by ampicillin (10 µg), ampicillin/sulbactam (10/10 µg), mezlocillin (75 µg), carbenicillin (100 µg), piperacillin/tazobactam (100/10 µg), cefazolin (30 µg), cefaclor (30 µg), cefepime (30 µg), cefoperazone (75 µg), and cefotetan (30 µg) from Becton Dickinson (Franklin Lakes, NJ, USA), Müeller Hinton medium were incubated at 37 °C for 24 h in both aerobic and anaerobic conditions. In anaerobic conditions, the media were placed in an anaerobic jar (BD BBL™ GasPak™), with a C02 gas generators envelope (BD BBL™) and another envelope of BD BBL™ GasPak™ anaerobic indicator placed on them.