Objectives To determine the dissemination and molecular characteristics of NDM-producing Escherichia coli strains from duck farms in south-east coastal China and their threats to human health. Methods A total of 232 NDM-producing E. coli were recovered from 1505 samples collected from 25 duck farms and their surrounding environments in five provinces in China. Resistance genes were confirmed using PCR. Genomic characteristics of the carbapenemase-producing isolates were determined by WGS and bioinformatic analysis. Results The rate of NDM-positive E. coli detected in samples from the five provinces ranged from 3.7% to 28.5%. There was substantial variation in the prevalence of NDM-positive E. coli from different duck farms in each province studied. Three variants (blaNDM-1, blaNDM-4 and blaNDM-5) were found in 232 NDM-positive E. coli; blaNDM-5 (94.8%, 220/232) was the most prevalent. WGS analysis indicated that ST746, ST48, ST1011 and ST167 E. coli isolates were prevalent in the current study and poultry was likely the primary reservoir for NDM-positive ST746 and ST48 E. coli in China. Phylogenomic analysis showed that NDM-positive E. coli isolates from ducks were closely related to those of human origin. In addition, WGS analysis further revealed that blaNDM co-existed with other antibiotic resistance genes, conferring resistance to nine classes of antimicrobials. Conclusions This study revealed that ducks farm in China are an important reservoir for NDM-positive E. coli and STs of the isolates showed obvious distinctive diversities in geographical distribution. The distribution and spread of NDM-positive E. coli in duck farms poses a threat to public health.

Objectives The emergence of carbapenemase-positive Enterobacteriaceae poses a serious threat to public health worldwide. Here we conducted a molecular surveillance study on carbapenem-resistant Enterobacteriaceae (CRE) colonization among migratory birds at Qinghai Lake in China. Methods A total of 420 samples from migratory birds and their surrounding environment were collected at three sites along the Qinghai Lake bird island. Carbapenem-non-susceptible isolates were identified by 16S rDNA sequencing and MALDI-TOF MS. Carbapenemase producers were determined by Carba NP testing. Antimicrobial susceptibility testing, transfer ability and PFGE were also performed, and 46 isolates from different pulsotypes were analysed by WGS. Results Three hundred and fifty isolates were carbapenemase producers based on Carba NP testing, while 233 Klebsiella spp. and 2 Escherichia coli isolates were NDM-5-carriers. PFGE was performed and showed that the isolates were grouped into five pulsotypes; among these, type A was predominant (86.7%, n = 202) and belonged to a novel Klebsiella lineage, ST1697. WGS analysis indicated that ST1697 strains may be a hybrid of the recombination of Klebsiella quasipneumoniae subsp. similipneumoniae and Klebsiella pneumoniae genomes. Conclusions This high frequency of carbapenemase producers in migratory birds is unexpected. These results provide new insight into the spread of antibiotic resistance, and highlight that continued vigilance for MDR carbapenemase-producing Enterobacteriaceae in migratory birds is urgently needed.

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CRKP is one of the most important pathogens, which can cause infection not only in humans but also in waterfowl. The discovery of bla NDM-5 -producing K. pneumoniae in waterfowl farms in recent years suggests that waterfowl are an important reservoir for bla NDM-5 -producing Enterobacteriaceae .