Antimicrobial susceptibility testing was carried out using the disk diffusion method [30 ] against 14 antimicrobials (Oxoid, Hampshire, UK): ceftiofur (CEF, 30 µg), ciprofloxacin (CIP, 5 µg), doxycycline (DOX, 30 µg), enrofloxacin (ENR, 5 µg), streptomycin (STR, 10 µg); florfenicol (FFC, 30 µg), fosfomycin (FOS, 200 µg); gentamicin (GEN, 10 µg), lincomycin-spectinomycin (LSC, 9 µg and 100 µg), marbofloxacin (MAR, 5 µg), neomycin (NEO, 30 µg), norfloxacin (NOR, 10 µg), sulfamethoxazole-trimethoprim (SXT, 23.75 µg and 1.25 µg), and tetracycline (TET, 30 µg). The results were interpreted according to EUCAST version 9.0 [31 ].
For colistin (colistin sulfate, Sigma–Aldrich, Y0000277), the minimal inhibitory concentration (MIC) was determined using a broth microdilution method. The results were interpreted using EUCAST version 9.0 [31 ,32 ]. The Escherichia coli ATCC 25922 strain was used as a control test. All strains were also screened for the presence of the mcr-1.1 gene by PCR [33 (link)].
For colistin (colistin sulfate, Sigma–Aldrich, Y0000277), the minimal inhibitory concentration (MIC) was determined using a broth microdilution method. The results were interpreted using EUCAST version 9.0 [31 ,32 ]. The Escherichia coli ATCC 25922 strain was used as a control test. All strains were also screened for the presence of the mcr-1.1 gene by PCR [33 (link)].