2.1 Bacterial isolates
Enterobacteriaceae isolates were isolated from fresh fecal
samples of animals at Zhengzhou Zoo, Henan province, China. Briefly,
fecal samples were collocated into Eppendorf tube with 500μL sterile
saline and shake gently and stood for 10 min. The supernatant was used
to inoculate onto the MacConkey Agar (Beijing SanYao Science &
Technology Development Co, Beijing, China) plate at
35oC for 18 hours. All the colonies with different
morphologies and colors were stored and subjected to further analysis.
Species identification was carried out using 16S rRNA sequence (TIANYI
HUIYUAN,China).
2.2 DrugSusceptibility Testing
Drug susceptibility testing was performed by broth microdilution method
(microbial susceptibility kit, BIO-KONT, China) according to the CLSI
guidelines (CLSI,2019). Fifteen antimicrobial drugs were used to screen
MDR in this study, including Ampicillin, Ampicillin/Sulbactam,
Piperacillin/Tazobactam, Aztreonam, Cefuroxime sodium, Ceftriaxone,
Cefepime, Ciprofloxacin, Levofloxacin, Meropenem, Colistin,
Chloramphenicol , Trimethoprim/ Sulfamethoxazole, Nitrofurantoinand Amikacin . The Drug susceptibility to Tetracycline andDoxycycline was tested by Kirby-Bauer disk diffusion method
(OXOID, UK), and E.coli ATCC25922 was used as a quality-control
strain.