Antibiotic susceptibility test
Antibiotic susceptibility was determined using the
SensititreTM panel (KRCDC2F; Thermo Fisher
Scientific, Waltham, MA, USA) with
the following antibiotics: ciprofloxacin (CIP, 0.03–0.5 µg), nalidixic
acid (NAL, 2–128 µg), imipenem (IMI, 1–8 µg), colistin (COL, 2–16
µg), ampicillin (AMP, 2–64 µg), tetracycline (TET, 2–128 µg),
chloramphenicol (CHL, 2–32 µg), azithromycin (AZI, 2–32 µg),
gentamicin (GEN, 1–64 µg), (STR, 2–128 µg), amikacin (AMI, 4–64 µg),
trimethoprim/sulfamethoxazole (SXT, 1/19–16/304), cefotaxime (FOT,
1–32 µg), ceftriaxone (AXO, 1–32 µg), cefoxitin (FOX, 4 - 32 µg), and
ceftazidime (TAZ, 1–16 µg), according to Clinical and
Laboratory Standards Institute guidelines (Wayne, PA, USA) . Briefly, 10
µL portions of Salmonella spp. strains (1 × 105cfu/mL) cultured overnight were thoroughly mixed with 11 mL of Muller
Hinton Broth with N -Tris (hydroxymethyl)
methyl-2-aminoethanesulfonic acid; 50 µL portions were placed in the
wells of the SensititreTM panel. The panel was sealed
with film, and the results were assessed manually after 24 h incubation
at 37°C. The MIC was recorded as the lowest concentration of antibiotic
that inhibit visible growth shown as turbidity or deposit of cells at
the bottom of a wall. Escherichia coli ATCC25922 was used as the
quality control standard.