Enrofloxacin

The Kirby–Bauer disk diffusion method described by Bauer et al. [28 (link)] was used to perform an antimicrobial susceptibility test on Mueller–Hinton agar (MHA) (HiMedia) using the following antibiotic disks: Cephalexin (30 μg/disk), ampicillin (10 μg/disk), streptomycin (10 μg/disk), gentamycin (10 μg/disk), colistin (10 μg/disk), enrofloxacin (5 μg/disk), nalidixic acid (30 μg/disk), ceftriaxone (30 μg/disk), ceftazi­dime (30 μg/disk), oxytetracycline (30 μg/disk), cefixime (5 μg/disk), and kanamycin (30 μg/disk) (HiMedia). The zone sizes of bacteria were compared with standards for resistance and sensitivity stated by the Clinical and Laboratory Standards Institute [29 ].

Different strains of various organisms isolated from urine samples of the infected animals were subjected to in vitro drug sensitivity testing, using 15 antimicrobials by the disc-diffusion method. With the help of a platinum loop, a small amount of test culture was transferred into a tube of brain heart infusion broth and incubated for 2-5 h at 37°C, to obtain turbidity. With the help of a sterile cotton swab, the broth culture was then evenly spread by smearing over the surface of BA/Mueller-Hinton agar plates. The antimicrobial discs were placed on the agar and gently pressed. These were then incubated at 37°C for 24 h. The sensitivity was observed on the basis of zone size interpretation chart, provided by the manufacturer. Different antimicrobials used were amikacin (10 mcg), amoxicillin (10 mcg), amoxicillin-clavulanic acid (30 mcg), ampicillin (25 mcg), cefoperazone (75 mcg), ceftriaxone (10 mcg), ceftriaxone–tazobactam (30mcg), chloramphenicol (25 mcg), cloxacillin (30 mcg), enrofloxacin (10 mcg), gentamicin (30 mcg), neomycin (30 mcg), oxytetracycline (30 mcg), penicillin-G (10 units), and streptomycin (25 mcg) (Hi-Media). To remain conservative in our estimates of resistance, isolates exhibiting intermediate zones of inhibition were interpreted as resistant.