Ofloxacin

The susceptibility of isolated strains was tested with 11 antibiotics belonging to the different classes (β-lactamines, cyclin, aminoglycosides, macrolides, quinolones, glycopeptides, phenicoles, and sulfa) by the disk diffusion method on Mueller-Hinton agar (Conda-Pronadisa, Madrid, Spain), according to the standards [9 ,10 ] recommended by the WHO. The antibiotic discs (BioRad, Marnes-la-Coquette, France) used are as follows: Penicillin (10 UI), cefoxitin (30 µg), tetracycline (30 µg), neomycin (30 µg), gentamicin (10 µg), erythromycin (15 µg), clindamycin (2 µg), ofloxacin (5 µg), vancomycin (30 µg), chloramphenicol (30 µg), and trimethoprim + sulfamethoxazole (1.25/23.73 µg).

The stock solutions of A. fruticosa fruits EO used for further assays were prepared 1:1 in DMSO (dimethyl sulfoxide). The antimicrobial activity screening was determined by employing an adapted disk diffusion technique, using 10 μL of stock solution of EO, which contained 295 mg EO solubilized in 1 mL of DMSO. The minimum inhibitory concentrations (MICs) were measured as described previously [43 ]. Briefly, serial dilutions of the stock solutions in liquid medium (Brain heart infusion broth for bacterial strains and Sabouraud broth for yeasts) were prepared in 96 wells plates (concentrations 29.5–0.46 mg/mL). Then 10 μL of the microbial suspension with the standard density of 0.5 Mc Farland was added to each well, positive and negative controls were used for each strain. The positive control antibiotic disks used in diffusion method include oxacillin (1 µg) (Bio-Rad, Hercules, CA, USA); ticarcillin-clavulanic acid (75 + 10 µg) (Bio-Rad); ceftriaxone (30 µg) (Bio-Rad); cefalexin (30 µg) (Bio-Rad); vancomycin (30 µg) (Bio-Rad); ofloxacin (5 µg) (Bio-Rad); colistin (10 µg) (Bio-Rad); erythromycin (15 μg) (Bio-Rad). The antibiotics were chosen according to CLSI and literature data for each tested strain. The plates were incubated for 24 h at 37 °C. The absorbance was measured at 620 nm with an Apollo LB 911.

The susceptibility of each Staphylococcus strain to antibiotics was determined by the diffusion method [35 ]. The tested antibiotics (Bio-Rad) were as follows: penicillin G (P 10 µg), amikacin (AK 30 µg), fosfomycin (FOS 50 µg), cefoxitin (FOX 30 µg), gentamycin (GEN 10 µg), erythromycin (E 15 µg), lincomycin (MY 15 µg), ciprofloxacin (CF 5 µg), ofloxacin (OFX 5 µg), amoxicillin (AMO 20 µg), cefotaxime (CTX 30 µg), tetracycline (TET 30 µg), trimethoprim-sulfamethoxazole (SXT 23.75 µg), amoxicillin-clavulanic acid (AMC 20 µg), and fusidic acid (FD 10 µg).