Study On Molecular Epidemiology Of NDM-5 Producing Enterobacteriaceae In China

Objective To explore the drug resistance and molecular epidemiology characteristics of the clinical carbapenems resistance isolates of Escherichia coli and Klebsiella pneumonia so as to provide the guidline for the prevention and control of hospital infection.Methods From March 2015 to December 2016,76 strains of carbapenems resistance Enterobacteriaceae,including 52 Escherichia coli and 24 Klebsiella pneumoniae were isolated from clinical specimens.The strains were identified by vitek-2 compact automatic（French biomerieux）.The extended spectrum beta-lactamases（ESBLs）,carbapenemases,aminoglycosides and quinolones genes,were amplified by polymerase chain reaction（PCR）,and confirmed by sequenceing.The The clonal relatedness of the strains were done by Multilocus sequence typing（MLST）and Pulsed field gel electro-phoresis（PFGE）.The plasmid conjugation t,PCR-based replicon typing（PBRT）method and Southern hybridization were carried out to analyze plasmid characteristics.Results The 22 out of total 76 strains,including 20 Escherichia coli（ECO1²0）and 2Klebsiella pneumonia（KPN1²）,habored bla_NDM-5 gene.The twenty two isolates also carried bla_OXA1,bla_CTX-M-55,bla_TEM-1,qnrS1,qnrS2 and aac（6’）-Ib genes.A great diversity of MLST types was observed among NDM-5-producing E.coli isolates.The ST167 were the most prevalent 45.5%（10/22）,and the other sequence type（ST）were ST410 13.6%（3/22）,ST617 9%（2/22）,ST46,ST453,ST448,ST648 and ST6388 4.5%（1/22）.The two strains of Klebsiella pneumoniae were ST313 and ST785.PFGE revealed that the Dice similarity with BioNumerics 6.0 were 85%in eight ST167Escherichia coli（ECO4、6、8、16、17、18、19、20）,84.4%in three ST410 Escherichia coli and 84.9%in two ST617 Escherichia coli,respectively and that the Dice similarity with that software was 74.3%between ST313 and ST785 Klebsiella pneumonia.The plasmids carrying bla_NDM-5 in 16 strains of the 20 Escherichia coli and in 1 strains of the 2Klebsiella pneumoniat can be transferred through conjugation.The S1 PFGE,PCR-based replicon typing（PBRT）and Southern hybridization with a NDM-specific probe showed that the bla_NDM-5 gene was located on nearly 46 kb Inc X3 plasmid in both Escherichia coli and Klebsiella pneumoniae.Conclusion The Escherichia coli ST167 carring bla_NDM-5 gene may be predominent clone in the region and that all of these NDM-5-producing isolates epidemically belong to sporadic cases.The bla_NDM-5 resistance gene carried by the strain is located on the IncX3plasmid of 46 kb,The IncX3 plasmid belongs to the narrow host plasmid and can undergo conjugation between the same species or different species.The public health authorities should further strengthen the monitoring of carbapenem-resistant Enterobacteriaceae（CRE）and the reasonable use of carbapenems antibiotics for the prevention and control of the hospital infection.