Objective To analyze the epidemiological characteristics of mobile colistin resistance(mcr)genes in global Klebsiella pneumoniae(K.pneumoniae).Methods The genomes of K.pneumoniae were downloaded from the NCBI genome database by the As-pera software.After quality filtering using the CheckM v1.1.3 and Quest 5.0.2 software,the genomes were annotated using the Prokka v1.13.All the mcr gene sequences were downloaded from the NCBI website and a database was built using the makeblastdb command.Then,a self-made Perl script program was used to extract the nucleotide sequences of all genes from the annotation file as Query,and the local BLASTN analysis was performed to obtain mcr-positive strains.The gene sequence files and Profiles files of 7 housekeeping genes of K.pneumoniae were downloaded from the PubMLST website as the database,and the nucleotide sequences of the genes were extracted as Query using a self-made Perl script program.The local BLASTN analysis was implemented to determine the sequence type(ST)of each genome.Meta information of each strain,including isolation source,sample type,country,and date,were extracted in batch from the GenBank file of the downloaded K.pneumoniae genomes using a self-written Perl program to analyze the distribution characteristics of mcr-positive strains.The distribution differences of the mcr between different ST types were compared by the Chi-square test.Results Among the 11 429 global K.pneumoniae genomes included in this study,229 mcr genes were detected from 207 strains.Six variants of mcr were identified,mainly mcr-1(87/229,38.0％),mcr-8(59/229,25.8％),and mcr-9(59/229,25.8％).76 STs were identified from 207 strains,with ST15(21/207,10.1％),ST43(17/207,8.2％),ST11(16/207,7.7％),and ST 147(16/207,7.7％)being the predominant.Among 87 mcr-1 positive strains,31 STs were found,with ST43(17/87,19.5％)and ST15(10/87,11.5％)being the main ones.Among 59 mcr-8 positive strains,17 STs were identified,with ST43(17/59,28.8％)and ST11(9/59,15.3％)being the predominant.Among 59 mcr-9 positive strains,27 STs were detected,with ST147(11/59,18.6％)and ST274(11/59,18.6％)being the main ones.There were statistical differences in the variants of mcr genes carried by different ST types.The mcr-positive K.pneumoniae came from 28 countries across five continents worldwide,led by China(68/207,32.9％)and Thailand(45/207,21.7％),which were mainly from the human body(100/207,48.3％)and had a concentrated outbreak time from 2015 to 2018.Conclusion Among the global K.pneumoniae,the prevalence of mcr is mainly domina-ted by mcr-1,mcr-8,and mcr-9.The dominant clones of mcr-1 are mainly ST15 and ST43,while those of mcr-8 are mainly ST11 and ST43.The popularity of mcr-9 is mainly based on ST147 and ST274.Strengthening the monitoring of such bacteria may play an impor-tant role in preventing and controlling nosocomial infections.

Objective To detect and analyze the drug resistance characteristics,phylogenetic typing,and virulence gene distribution of Escherichia coli(E.coli)in blood culture.Methods The strains of E.coli isolated from consecutive non-repetitive blood cultures in our hospital from January 1,2019 to December 13,2020 were collected.The sensitivity of E.coli to 17 antibiotics was determined u-sing the micro-broth method.The bacterial genomic DNA was extracted using the boiling method,and then the arpA,chuA,yjaA,TspE4C2,ArpAgpE and trpAgpC genes were detected by PCR to determine the bacterial phylogroup.The virulence genes,including iutA,fimH,fyuA,kpsMT Ⅱ,cnf1,cvac,hlyA,traT,kpsMT Ⅲ,and PAI,were detected using the multiplex PCR.The differences in drug resistance and virulence gene distribution among different phylogroups were analyzed by the Chi-square test.Results 270 strains of E.coli in blood culture showed high resistance rates to ceftriaxone,compound sulfamethoxazole,ampicillin,ampicillin sulbactam,cefazolin,and ciprofloxacin,all exceeding 50.0％.They had good susceptibility to imipenem,ertapenem,amikacin,and piperacillin tazobactam,with resistance rates all below 5.0％.The most common phylogroups were types B2 and D,accounting for 38.0％and 16.2％,respectively,while type E and hidden branch type I were relatively rare,accounting for less than 1.0％.The virulence gene analysis revealed that the distribution rates of fimH and fyuA genes were the highest,both above 99.0％.The distribution rates of kpsMT Ⅲ,hlyA,and cvaC genes were relatively low,all below 20.0％.The Chi-square test showed that the distribution rates of viru-lence genes such as iutA,fimH,fyuA,kpsMT Ⅱ,cnf1,and PAI in the B2 group were significantly higher than those in the non-B2 group(P<0.05).The distribution rates of iutA,fyuA,kpsMT Ⅱ,cnf1,and PAI genes in the B2 group were significantly higher than those in the D group(P<0.05).Conclusion When treating bloodstream infections caused by E.coli,caution should be exercised in the use of drugs such as ceftriaxone,compound sulfamethoxazole,ampicillin,ampicillin sulbactam,cefazolin,and ciprofloxacin.When bloodstream infections are caused by phylogroup B2 E.coli,middle-stream urine culture should be performed simultaneously to confirm the source of infection and monitor the success rate of treatment.