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.