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 Gram-stain-positive, facultatively aerobic, non-motile and rod- to coccoid-shaped bacterial strains, 23H37-10T and 4HC-13, were isolated from the faeces of greater white-fronted geese (Anser albifrons) at Poyang Lake, Jiangxi Province, PR China. Optimal growth was observed at 35–37 °C, pH 7.0–8.0 and with 0.5–1.5 % (w/v) NaCl. The 16S rRNA gene sequences of strains 23H37-10T and 4HC-13 were identical. Phylogenetic and phylogenomic analyses indicated that strains 23H37-10T and 4HC-13 formed an independent cluster within the genus Corynebacterium and showed 98.8, 97.4, 97.4 and 97.2 % 16S rRNA gene sequence similarity to Corynebacterium urogenitale LMM 1652T, Corynebacterium urealyticum DSM 7109T, Corynebacterium falsenii DSM 44353T and Corynebacterium jeikeium NCTC 11913T, respectively. Cells contained C18 :1 ω9c, C18 : 0 and C16 : 0 as the major cellular fatty acids and MK-9 (H2) as the predominant respiratory quinone. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidyl inositol mannosides, two unidentified phospholipids, four unidentified glycolipids and one unidentified lipid. Strain 23H37-10T contained mycolic acids, with meso-diaminopimelic acid and arabinose as the major whole-cell hydrolysates. The genome G+C content of strains 23H37-10T and 4HC-13 was 55.2 mol%. The digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strains 23H37-10T and 4HC-13 were 94.4 and 99.6 %, respectively. Strains 23H37-10T and 4HC-13 had dDDH and ANI values of less than 70 and 96 % with all available genomes of the genus Corynebacterium , respectively. The differential genotypic inferences, together with phenotypic and biochemical characteristics, suggested that strains 23H37-10T and 4HC-13 represent a novel species within the genus Corynebacterium , for which the name Corynebacterium anserum sp. nov. is proposed. The type strain is 23H37-10T (=GDMCC 1.1737T=KACC 21672T).

Two rod-shaped and Gram-stain-positive bacteria (strains C64T and 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 to Bowdeniella nasicola DSM 19116T (92.1 %). Phylogenetic/phylogenomic analyses indicated that strains C64T and C62 clustered independently in the vicinity of the genera Varibaculum , Winkia and Mobiluncus within the family Actinomycetaceae , 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 family Actinomycetaceae were around the genus threshold value (45–65 %). The major cellular fatty acids of the strains were C18 : 1ω9c and C16 : 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 C64T and C62 represent a novel species belonging to a novel genus within the family Actinomycetaceae , for which the name Nanchangia anserum gen. nov., sp. nov. is proposed. The type strain is Nanchangia anserum C64T (=CGMCC 1.18410T=GDMCC 1.1969T=KCTC 49511T=KACC 22143T).

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