Characterization of NDM-5-Producing Escherichia coli Strains Isolated from Pediatric Patients with Bloodstream Infections in a Chinese Hospital

Escherichia coli (E. coli) bloodstream infections (BSIs) are among the most predominant causes of death in infants and children worldwide. NDM-5 (New Delhi Metallo-lactamase-5) is responsible for one of the main mechanisms of carbapenem resistance in E. coli. To analyze the phenotypic and genomic characteristics of NDM-5-producing E. coli from bloodstream infections (BSIs), a total of 114 E. coli strains was collected from a children’s hospital in Jiangsu province, China. Eight bla(NDM-5)-carrying E. coli strains were identified which were all carbapenem-resistant and carried diverse antimicrobial resistance genes apart from bla(NDM-5). They belonged to six distinct sequence types (STs) and serotypes including one each for ST38/O7:H8, ST58/O?:H37, ST131/O25:H4, ST156/O11:H25 and ST361/O9:H30 and three strains are originating from a single clone belonging to ST410/O?:H9. Apart from bla(NDM-5), the E. coli strains isolated from BSIs also carried other β-lactamase genes, including bla(CMY-2) (n = 4), bla(CTX-M-14) (n = 2), bla(CTX-M-15) (n = 3), bla(CTX-M-65) (n = 1), bla(OXA-1) (n = 4) and bla(TEM-1B) (n = 5). The bla(NDM-5) genes were located on three different types of plasmids, which were IncFII/I1 (n = 1), IncX3 (n = 4) and IncFIA/FIB/FII/Q1 (n = 3). The former two types were conjugatively transferable at frequencies of 10(−3) and 10(−6), respectively. The dissemination of NDM-producing strains, which exhibit resistance to the last-line antibiotics, carbapenems, may increase the muti-antimicrobial resistance burden among E. coli BSIs and further threaten public health.