Emergence of Escherichia coli isolates producing NDM-1 carbapenemase from waterfowls in Hainan island, China

Carbapenems are traditionally recognized to be the last resort drugs to treat infections due to MDR organisms such as E. coli. As such, the emergence of New Delhi metallo-beta-lactamase-producing E. coli strains have become a challenging threat to the public health. In this regard, we examined the molecular characteristics of carbapenem-resistant E. coli (CRE) isolated from waterfowls in China's tropical island, Hainan. A total of 311 single E. coli strains were obtained from 20 various farms of healthy ducks and geese in 2 districts of Hainan island. The CRE strains were initially identified via phenotypic resistance and modified Hodge test. PCR assay and subsequent nucleotide sequencing were used to detect different types of carbapenemase encoding genes (bla(NDM), bla(VIM), bla(IMP), bla(OXA) and bla(KPC)). In addition, MLST and PFGE analyses were also performed. Among the 311 E. coli strains, 8 strains were detected to produce a single type of carbapenemase i.e. NDM-1 (2.6%). A total of 5 sequence types (STs) were observed, of which ST10 was the most prevalent accounting for 37.5% (3/8). Moreover, these 8 isolates yielded 6 different PFGE clusters but showed approximately related PFGE types, suggesting the propagation of similar clone between the farms. This is the first report on the identification of NDM-1-producing E. coli from waterfowls in Hainan island, China. Our results emphasize the need for better efforts to control the further spread of NDM-1-producing E. coli strains in this tropical island.