Non-O157 Shiga toxin-producing Escherichia coli (STEC) is an important pathogen that can cause zoonotic diseases. To investigate the antimicrobial resistance of STEC in China, non-O157 STEC isolates, recovered from domestic animals and humans from 12 provinces, were analyzed using antimicrobial susceptibility testing and whole genome characterization. Out of the 298 isolates tested, 115 strains showed resistance to at least one antimicrobial and 85 strains showed multidrug resistance. The highest resistance rate was to tetracycline (32.6%), followed by nalidixic acid (25.2%) and chloramphenicol and azithromycin (both 18.8%). However, imipenem and meropenem were effective against all isolates. Antimicrobial resistance patterns varied among strains from different sources. Strains from pig, sheep, humans, and cattle showed resistance rates of 100.0%, 46.9%, 30.3%, and 6.3% to one or more antimicrobials, respectively. Forty-three genes related to 11 antimicrobial classes were identified among these strains. The colistin-resistance gene mcr was only carried by strains from pigs. A new fosfomycin-resistant gene, fosA7, was detected in strains from humans, cattle, and sheep. Whole genome phylogenetic analysis showed that strains from the four sources were genetically diverse and scattered throughout the phylogenetic tree; however, some strains from the same source had a tendency to cluster closely. These results provide a reference to monitor the emergence and spread of multidrug resistant STEC strains among animals and humans. Furthermore, with a better understanding of antimicrobial genotypes and phenotypes among the diverse STEC strains obtained, this study could guide the administration of antimicrobial drugs in STEC infections when necessary.

Two rod-shaped and Gram-stain-positive bacteria (strains C64^Tand C62) were isolated in 2020 from faeces of greater white-fronted geese (Anser albifrons) from Poyang Lake, PR China. Their optimal growth conditions were at 37 °C, pH 7.0 and with 0.5 % (w/v) NaCl. The two isolates showed a highest 16S rRNA gene sequence similarity toBowdeniella nasicolaDSM 19116^T(92.1 %). Phylogenetic/phylogenomic analyses indicated that strains C64^Tand C62 clustered independently in the vicinity of the generaVaribaculum,WinkiaandMobiluncuswithin the familyActinomycetaceae, but could not be classified clearly as members of any of these known genera. The average amino acid identity values between our isolates and available genomes of members of the familyActinomycetaceaewere around the genus threshold value (45–65 %). The major cellular fatty acids of the strains were C_18 : 1ω9cand C_16 : 0. The predominant polar lipids were phosphatidylinositol, phosphatidylglycerol, phosphatidylcholine, diacylglycerol, triacylglycerol and cardiolipin. The amino acid composition of peptidoglycan contained alanine, glutamic acid and glycine. The major respiratory menaquinones were MK-8(H₄) and MK-9(H₄). The whole cell sugars included galactose, arabinose and glucose. On the basis of the results of the 16S rRNA gene sequences comparison, whole-genome phylogenomic analysis, phenotypic and chemotaxonomic characteristics, we propose that strains C64^Tand C62 represent a novel species belonging to a novel genus within the familyActinomycetaceae, for which the nameNanchangia anserumgen. nov., sp. nov. is proposed. The type strain isNanchangia anserumC64^T(=CGMCC 1.18410^T=GDMCC 1.1969^T=KCTC 49511^T=KACC 22143^T).