Genomic Characterization of ESBL/AmpC-Producing in Stray Dogs Sheltered in Yangzhou, China.

Purpose: Limited data are available on the prevalence and antimicrobial resistance of extended spectrum β-lactamase- (ESBL) and AmpC β-lactamase-producing in stray dogs. We aimed to investigate the genomic characteristics of ESBL/AmpC-producing 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 cefotaxime-resistant isolates by whole genome sequencing.

Results: We identified 80 cefotaxime-resistant isolates (51.3%), 59 isolates (73.8%) from feces and 21 (26.2%) from the environment. Whole-genome sequencing analysis showed that (n=30) and (n=29) were the most prevalent genotypes. Two isolates only carried the AmpC β-lactamase gene ; one isolate had a combination of AmpC β-lactamase gene and ESBL β-lactamase gene . Other important resistance genes such as , , , , (A), , and were also detected. The serotype combination was highly abundant, with O10:H25 predominating (n=12). Most cefotaxime-resistant 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 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/AmpC-producing and highlights the possible role of stray dogs as an antibiotic resistance gene reservoir.