Norfloxacin

We determined antimicrobial drug susceptibility by the disk-diffusion method on Mueller-Hinton agar plates as recommended by the Clinical Laboratory Standard Institute [19 ]. We tested the following antimicrobial agents: ampicillin 10 μg, tetracycline 30 μg, oxy-tetracycline 30 μg, which were used in the farms and the following agents used in the management of E.coli infections; amoxicillin/clavulanic acid 10 μg, cephalothin 30 μg, cefotaxime 30 μg, ceftazidime 30 μg, imipenem 10 μg, norfloxacin 10 μg, ciprofloxacin 5 ug, enrofloxacin 5 μg, amikacin 30 ug, chloramphenicol 10 μg, kanamycin 30 μg, streptomycin 10 μg, gentamicin 10 μg and sulfamethoxazole/trimethoprim (cotrimoxazole) 25 μg (Mast Diagnostics). Results obtained were used to classify isolates as being resistant or susceptible to a particular antibiotic using standard reference values [19 ].

The antimicrobial susceptibility of Shigella species was evaluated using the disk diffusion method (Kirby–Bauer test) on Mueller Hinton agar (Merck, Germany), in accordance with the recommendations provided by Clinical and Laboratory Standards Institute (CLSI 2022) guidelines [16 ]. Following antibiotic disks were used: amikacin (AN/30 μg), chloramphenicol (C/30 μg), trimethoprim–sulfamethoxazole (SXT/1.25/23.75 μg), nalidixic acid (NA/30 μg), norfloxacin (NOR/10 μg), ofloxacin (OFX/5 μg), ceftriaxone (CRO/30 μg), cefotaxime (CTX/30 μg), ceftazidime (CAZ/30 μg), ceftizoxime (CT/30 μg), cefixime (CFM/5 μg), azithromycin (AZM/15 μg), cefoxitin (FOX/30 μg), Amoxicillin (AMX/25), piperacillin–tazobactam (100/10 μg) (Mast Diagnostics, Merseyside, UK).
The phenotype(s) of Shigella isolates were classified as MDR (multidrug-resistant) when they displayed “non-susceptibility to at least one agent in three or more antimicrobial categories” [17 (link)].