Emergence of two Escherichia coli strains co-harboring mcr-1 and blaNDM in fresh vegetables from China

Two E. coli isolates concomitantly carrying mcr-1 and bla NDM-5/9 from leaf rape and spinach, respectively, were found and both isolates showed multidrug resistance. Notably, mcr-1-positive 690 harboring bla NDM-5 and 701 carrying bla NDM-9 belonged to ST156 and ST2847, respectively, similar to the prevalent MLST types of E. coli co-carrying mcr-1 and bla NDM from avian in our previous study. mcr-1 was on ~33-kb IncX4 plasmid or ~60-kb IncI2 plasmid, while bla NDM-5/9 was on ~46-kb IncX3 plasmid or ~120-kb untypable plasmid. The plasmids were highly similar to those from animals and clinical patients reported in various countries.Conclusion: E. coli isolates concomitantly carrying mcr-1 and bla NDM-5/9 in fresh vegetables may serve as a direct source of pathogens in humans, and such discovery in fresh vegetables emphasizes the importance of prompt surveillance and intervention in limiting the spread of E. coli co-carrying bla NDM and mcr-1. To our knowledge, this is the first report of Enterobacteriaceae co-carrying bla NDM and mcr-1 in fresh vegetables.