Molecular Typing Study Of Carbapenem-Resistant Acinetobacter Baumannii

Objectiive:To explore the application of three different typing methods including PFGE,MLST and cgMLST in the traceability of carbapenem-resistant Acinetobacter baumannii(CRAB)and reveal the spreading rule of CRAB.Methods:CRAB strains were collected from three hospitals in Taizhou from 2016 to 2018 and reviewed by microbroth dilution method.The common carbapenemase genes(blaOXA-23,blaOXA-24 and blaOXA-58)were verified by PCR and sequencing.PFGE was used for homology analysis and strains of the same PFGE type were sequenced by WGS technology.The resistant genes,MLST type and cgMLST type were analyzed through the WGS results.Combined with the cgMLST type and clinical information of patients,the clinical dissemination path was drawn.Result:A total of 149 CRAB strains were collected,of which 146 strains(98%)carried blaOXA-23,2 strains carried blaOXAx-58 and no bvlaOXA-24 was detected.The strains were divided into 15 types(A to O)by PFGE,73 strains(49%)of which belonged to type A,the main clone.The resistant genes analysis of type A strains showed that all strains carried blaOXA-23,blaOXA-25,aph(6)-ld and strA,and>70%strains carried blaTEM-1,arm,aph(3')-Ia,msr(E),mph(E),tet(B).The results of MLST typing showed that all 73 strains belonged to ST2(Pasteur scheme).And based on the Oxford scheme of MLST,there are 6 STs:ST195,ST208,ST136,ST369,ST784 and STnovel.According to cgMLST,73 strains could be divided into 9 clusters,the largest cluster accounted for 46.6%(34/73).Combined with clinical information,it was found that most patients had experienced bed transfer or hospital transfer.There Were 4 cgMLST clusters from the same department in one hospital.Conclusion:CgMLST shows a higher resolution than PFGE and MLST,and has a higher application value in CRAB traceability research.The results of cgMLST revealed that the transfer of patients with CRAB in different hospitals or departments was an important risk factor for CRAB spreading.