| Objective:Methicillin-resistant Staphylococcus aureus(MRSA)is one of the clinically important pathogenic bacteria that can cause infections related to the respiratory tract,skin and soft tissues,blood,and medical devices related infections.MRS A often carries a variety of drug resistance genes and virulence genes,making the strains insensitive to commonly used antibacterial drugs,causing infections to be difficult to control and increasing the difficulty of treatment.In addition,MRSA often carries biofilm-related genes to form biofilms on invasive medical devices or ventilators in the body,increasing the difficulty of treatment.In this study,the MRSA strains detected in a top three hospital in Yunnan Province from 2017 to 2019 were used as research objects to explore the resistance phenotypes,common resistance genes,virulence genes,and biofilm-related gene carrying status of the strains;Spa classification,MLST classification,SCCmec classification characteristics and epidemiological characteristics to supplement the local MRSA molecular epidemiological data;provide a valuable theoretical basis for the clinical treatment of MRSA and the prevention and control of infection.Methods:1.Collect the strains detected and preserved in the Medical Laboratory Department of the First Affiliated Hospital of Kunming Medical University from June 2017 to December 2019,and be manually identified by routine,VITEK-2 automatic microbial instrument,double PCR amplification of mecA And femB gene,a total of 65 MRSA strains were included;2.Use K-B method and MIC method to test the sensitivity of MRSA commonly used clinical antibacterial drugs;3.Design and synthesize primers according to the literature,and use polymerase chain reaction(PCR)to amplify MRSA drug resistance genes such as mecC,aac(6’)/aph(2")、Aph(3)-Ⅲ、ant(4’)-Ia,ermA,tetM,qnrA;virulence genes such as PVL,fnbA,SEA,SEB,TSST-1,hla;biofilm related genes such as icaA,sarA,fnbB;4.Molecular genotyping of MRSA using spa typing,multilocus sequence typing(MLST typing)and Staphyloccoccal Cassette Chromosome mec typing(SCCmec typing);MLST results were analyzed with MEGA7.0 software for genetic information;5.Compare the drug resistance of ST59 group and non-ST59 group strains.SPSS 20.0 was used for statistical analysis.Fisher’s exact probability method was used for the comparison of count data groups(P＜0.05 indicated that the difference was statistically significant).Results:1.Specimen type and source:65 strains of MRSA were mainly isolated from sputum,secretions and blood,accounting for 40.00%,21.54%and 20.00%respectively,followed by pus,ascites,alveolar fluid and pleural fluid,accounting for 13.85%and 1.54%respectively,1.54%and 1.54%;the source distribution of departments is mainly respiratory medicine and neurology,accounting for 13.85%and 10.77%respectively;2.Resistance phenotype:The resistance rate of 65 strains of MRSA to penicillin and oxacillin is 100.00%,and the resistance rate to erythromycin,clindamycin and tetracycline is higher,all exceeding 50.00%;Damycin,rifampicin,and co-trimoxazole all have different degrees of resistance;the multiple resistance rate is as high as 92.31%.No strains resistant to teicoplanin,quinupristin/dalfopristin,tigecycline,vancomycin and linezolid were found;3.Gene carrying rate:Aminoglycoside resistance genes aac(6’)/aph(2")、Aph(3)－Ⅲ、ant(4’)-Ia carry rates are higher,respectively 43.08%,55.38%,15.38%;macrolide resistance gene ermA and tetracycline resistance gene tetM were also carried at higher rates,respectively,60.00%and 50.77%;quinolone resistance gene qnrA was carried at a lower rate,10.77%;A new β-lactam resistance gene mecC was found;the carrying rates of virulence genes PVL,fnb A,SEA,SEB,TSST-1 and hla were 33.85%,89.23%,83.08%,76.92%,15.38%,92.31%,respectively;The biofilm-related genes icaA,sarA,and fnbB have a high carrying rate,98.46%,95.38%,and 86.15%,respectively;4.Molecular typing:There are 17 spa types in 65 strains of MRS A,the main types are t437,t030 and t034;there are 16 ST types,the main types are ST59,ST239 and ST338;there are 4 SCCmec types,Respectively,SCCmec Ⅲ,Ⅳa,Ⅴ,Ⅳb,accounting for 46.15%,30.77%,16.92%and 6.15%respectively.The resistance rate of ST59 strain to quinolones,gentamicin and rifampicin was significantly lower than that of non-ST59 strains;5.ST59-MRSA-Ⅳa-t437 and ST239-MRSA-Ⅲ-t030 are the main ST-MRS A-SCCmec-spa types popular in this area.Conclusions:1.The MRSA infection sites of the First Affiliated Hospital of Kunming Medical University are mainly respiratory tract,skin and soft tissue infections,and there are no obvious aggregation clones in the distribution of departments;2.No strains resistant to teicoplanin,quinupristin/dalfopristin,tigecycline,vancomycin and linezolid are found,and the resistance to other types of antimicrobial drugs is serious;3.ST59-MRSA-Ⅳa-t437 and ST239-MRSA-Ⅲ-t030 are the most prevalent types;4.The hospital’s MRSA has high overall drug resistance,virulence,biofilm related gene carrying rate,high multiple drug resistance rate,strong virulence,and the possibility and potential of biofilm formation is greater,especially in the inhalation of respiratory medicine,blood medicine Patients with relatively frequent sexual operations pose a more serious threat.Therefore,clinical departments should reasonably select antimicrobial drugs based on drug sensitivity results,strengthen the monitoring of multi-drug resistant bacteria,and take appropriate measures to control MRSA infection and transmission based on molecular epidemiological results. |
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