Tigecycline has been regarded as one of the last-resort antibiotics available for the treatment of infections caused by carbapenem-resistant Enterobacterales . The plasmid-mediated resistance-nodulation-division–type efflux pump gene cluster tmexCD - toprJ is a newly identified tigecycline resistance determinant.

Limited data are available on the prevalence and antimicrobial resistance of extended spectrum β-lactamase-(ESBL) and AmpC β-lactamase-producing Escherichia coli in stray dogs. We aimed to investigate the genomic characteristics of ESBL/AmpCproducing E. coli isolated from stray dogs sheltered in Yangzhou, China. Methods: We collected 156 samples including 115 fecal swabs, 35 kennel floor swabs, two breeder hand and shoe sole swabs, and four feed samples. The isolates were tested for resistance by antimicrobial susceptibility testing and further analyzed for cefotaximeresistant E. coli isolates by whole genome sequencing. Results: We identified 80 cefotaxime-resistant E. coli isolates (51.3%), 59 isolates (73.8%) from feces and 21 (26.2%) from the environment. Whole-genome sequencing analysis showed that bla CTX-M-15 (n=30) and bla CTX-M-55 (n=29) were the most prevalent genotypes. Two isolates only carried the AmpC β-lactamase gene bla CMY-2 ; one isolate had a combination of AmpC β-lactamase gene bla DHA-1 and ESBL β-lactamase gene bla CTX-M-14 . Other important resistance genes such as bla OXA-10 , bla TEM-1B , bla TEM-135 , bla TEM-106 , tet(A), qnrS1, qnrB4, and oqxAB were also detected. The serotype combination was highly abundant, with O10:H25 predominating (n=12). Most cefotaxime-resistant E. coli isolates belonged to phylogroup A (62.5%, n=50), followed by phylogroup B1 (26.3%, n=21). Thirty different sequence types (STs) and 27 distinct plasmid replicons were identified, among which ST2325 (n=12) and IncFII (n=38) was the most frequent ST and plasmid, respectively. ESBL/AmpC-producing isolates were divided into four major clades; clade IV was the primary lineage containing 37 isolates from feces and 13 from the environment. Three high-risk E. coli clone ST23 strains and one ST10 strain belonged to clades III and IV, respectively. Conclusion:Our study provides a comprehensive overview of resistance profiles and genomic characteristics in ESBL/AmpCproducing E. coli and highlights the possible role of stray dogs as an antibiotic resistance gene reservoir.

Klebsiella quasipneumoniae isolate SBH035 was recovered from a patient in Jiangsu Province, China. The isolate showed resistance to ampicillin, cefazolin, cefotaxime, meropenem, ceftazidime–avibactam, and fosfomycin. The carbapenemase-encoding gene bla NDM-7 was identified, and whole genome sequencing analysis indicated that bla NDM-7 was located in an IncX3 plasmid with a conserved structure of IS 26 -Δ cutA-tat-trpF-ble MBL -bla NDM-7 -IS Aba125 -IS 3000 -ΔTn2. To date, this is the first identification of a bla NDM-7 -harboring IncX3 plasmid in ST196 K. quasipneumoniae from a patient in China. Greater attention to controlling the dissemination of IncX3 plasmids is needed owing to potential horizontal transfer via mobile genetic elements.