Objective To investigate infection status and antimicrobial resistance mechanism of methicillin-resistant Staphylococcusaureus(MRSA),and provide reference for the rational antimicrobial use in clinic. Methods Staphylococcusaureus (SA)isolated from various specimens in Xuzhou area in 2012-2015 were collected,MR-SA strains were preliminarily screened by cefoxitin disk diffusion method,and confirmed by amplification of mecA gene,antimicrobial resistance of MRSA was determined by Kirby-Bauer method,minimal inhibitory concentration (MIC)was measured by E-test method,genotypes of staphylococcal chromosomal cassette mec(SCCmec)were de-termined by multiplex PCR. Results A total of 116 strains of MRSA were identified among 210 SA strains in 2012-2015,114 of which were positive for mecA gene,the total detection rate of MRSA was 55.24% . Susceptibility rates of MRSA to vancomycin,quinupristin/dalfopristin,and linezolid were all 100% ,resistance rates of MRSA to chloramphenicol and furantoin were both low,which were 15.52% and 1.72% respectively,resistance rates of MR-SA to 10 kinds of antimicrobial agents were all>80% ;resistance rates of MRSA to penicillins,aminoglycosides, macrolides,quinolones,sulfanilamide,rifampicin,tetracycline,and clindamycin were all higher than methicillin-sensitive Staphylococcusaureus(MSSA). MICs of vancomycin to MRSA in 2012-2015 were all 1.0μg/mL,MIC90 were all 1.5μg/mL,one MRSA isolate was with a vancomycin MIC of 2.0μg/mL in 2015. MRSA typing results of 116 MRSA isolates showed that SCCmec II,SCCmec III,and SCCmec IV accounted for 9.48% (n= 11),73.28% (n= 85),and 1.72% (Iva,n= 2;IVb,n= 2)respectively,13.79% (n= 16)of MRSA isolates were nontypeable, SCCmec I and SCCmec V type strains were not found. Conclusion MRSA is seriously multidrug-resistant,the drift has not been discovered in MIC value of vancomycin against MRSA,the major SCCmec genotype of MRSA is SCCmec III,infection control measures should be taken to control MRSA infection.

Objective To analyze the resistance mechanism,characteristics of drug sensitivity,and homology of polymyxin resistant Escherichia coli,and provide molecular epidemiological basis for the effective prevention and control of its outbreak and epidemic.Methods The strains of polymyxin resistant Escherichia coli isolated from our hospital during May 2016 and June 2022 were collected.The PCR technology was used to screen for the mobile colistin resistance(MCR)gene and the micro broth dilution method was used to determine the minimum inhibitory concentration.The clinical data of the patients were collected.The homology of the collected strains was analyzed by the pulsed field gel electrophoresis(PFGE).One of the strains was performed whole genome sequencing.Results Four strains of polymyxin resistant Escherichia coli carrying the MCR-1 gene were isolated and identified.Except for being sensitive to tigecycline,all four strains showed varying degrees of resistance to the vast majority of clinically common antibiotics.Clinical data showed that no polymyxin was used in the patients with polymyxin resistant Escherichia coli.The four strains of bacteria could be divided into two types,including three strains of type A and one strain of type B.The whole genome sequencing analysis of one of the bacteria revealed that the MCR-1 gene was located on a plasmid with a size of 70 kb.Conclusion The Escherichia coli carrying the MCR-1 gene has a potential threat to clone transmission and exhibits high resistance to common antibiotics in clinical practice,posing a serious challenge to clinical treatment.Therefore,it is necessary to strengthen protective measures to prevent its outbreak and epidemic.