Cefazolin

The Kirby–Bauer disc diffusion test was performed using Mueller–Hinton agar plates (Becton, Dickenson and Company) according to Clinical and Laboratory Standard Institute standards [23] using the following antimicrobials: ampicillin (10 µg), cefazolin (30 µg), kanamycin (30 µg), streptomycin (10 µg), tetracycline (30 µg), chloramphenicol (30 µg), fosfomycin (50 µg), colistin (10 µg), sulfamethizole (250 µg), and nalidixic acid (30 µg) (Becton, Dickinson and Company).

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.

Antimicrobial susceptibility testing (AST) was conducted on the isolates using the disk-diffusion method according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI) [11 ]. Antimicrobial substances included ampicillin, amoxicillin/clavulanic acid, cefazolin, cefotaxime, cefepime, nalidixic acid, ciprofloxacin, sulfamethoxazole-trimethoprim, fosfomycin, azithromycin, nitrofurantoin, streptomycin, kanamycin, gentamicin, chloramphenicol, and tetracycline (Becton, Dickinson, Heidelberg, Germany). Results were interpreted according to CLSI breakpoints for human clinical isolates [11 ]. Multidrug resistance (MDR) was defined as resistance to three or more classes of antimicrobials, counting beta-lactams as one class.