| Objectives:To investigate the distribution and drug resistance rate of Methicillin-resistant Staphylococcus aureus(MRSA)in Guiyang area,and to provide laboratory evidence for reasonable selection of antibiotics in clinic.To analyse the homology of MRSA isolates in order to offer laboratory evidence and control strategy for molecular epidemic spread of drug-resistant strains.Methods:1.The staphylococcus aureus(SA)isolates were collectedfrom wound secretions,sputum,blood in patients of a tertiary hospital in Guizhou province from January 2018 to September 2018.Preliminary pathogen identification and the susceptibility test were performed by Phoenixtm-100 automatic microbial analysis system.M-H paper method was used to confirm the phenotypes of strains.Results were analyzed by the Clinical and Laboratory Standards Institute(CLSI).2.Resistance gene mecA,and virulence gene fibronectin binding protein A(fnbA),intracellular adhesion A(icaA),exfoliative toxin A(eta),Panton-Valentine Leukocidin(PVL)were detected by polymerase chain reaction(PCR).Amplification products were sequenced and compared with the GenBank database.3.The SCCmec genotype of MRSA was determined by multiplex polymerase chain reaction(Multi-PCR).4.PCR amplifications of seven key genes(arcC,aroE,glpF,gmk,pta,tpi,yqiL)were analyzed by Multilocus sequence typing(MLST).The MLST results were analyzed by MEGA 7.0 and eBURST software for genetic information.5.The resistance and virulence of ST59 and non-ST59 group,HA-MRSA and CA-MRSA group were compared.The results were analyzed by SPSS 22.0.T-test was applied to compare the continuous variables and?~2-test was adopted to compare categorical data.Small probability event was measured by Fisher's exact probability test(P<0.05 indicates that the difference is statistically significant).Results:1.A total of 60 MRSA isolates were collected.53 isolates were selected after excluding duplicates,colonization,contamination and bacterial identification.Drug sensitivity test showed that all 53 strains were resistant to penicillin,oxacillin and the resistant rate to clindamycin and erythromycin were 81.13%and 84.90%,respectively.Resistance rates of tetracycline,aminoglycoside gentamicin,quinolone ciprofloxacin,cotrimoxazole,and rifampicin were 33.96%,15.09%,15.09%,7.55%,and 16.98%,respectively.No strain was found to be resistant to quinupristin/dalofoprene,linezolid,vancomycin.2.Strains were isolated from sputum samples was 33.96%,following by those from wound secretions,accounting for 32.08%.In different clinical departments,Orthopaedics,Pediatrics,and ICU ranked the top three,accounting for 16.98%,15.09%,and 9.43%,respectively.3.Among all the tested strains,51 strains detected mecA gene,with a positive rate of 96.22%.The virulence gene detection rate of fnbA and ica were both100%.The PVL gene was detected about 30.19%,principally in CA-MRSA(15/16,93.75%),and no eta gene was detected.4.Type IVa was principally SCCmec genetype and detected in 24 strains,accounting for 45.28%.Type III genotype was detected in 8 strains accounting for 15.09%.Type II and type V respectively were detected in 1 strain,with 19strains were untyped.5.53 isolates were detected by MLST and divided into 13 types.ST59(26/53,49.06%)was the dominant type,and its allele spectrum was19-23-15-2-19-20-15-27.Followed by ST4240(6/53,11.32%),ST239(5/53,9.43%),ST5(3/53,5.66%),ST45(3/53,5.66%),ST6(2/53,3.77%),ST630(2/53,3.77%),and 1 strain of ST1,ST88,ST188,ST338,ST398 and ST39,respectively.6.Population structure of eBURST software demonstrated that 13 types can be divided into two clonotypes(ST239-ST630,ST59-ST338-ST4240),including one CC338 clone complex(ST59-ST338-ST4240),and eight unique types(ST1,ST5,ST6,ST45,ST88,ST188,ST398,ST3935).7.Clinical data analysis indicated that the resistance rate of ciprofloxacin,rifampicin and tetracycline in non-ST59 group was higher than that in ST59 group(P<0.05).The resistance rate of CA-MRSA to ciprofloxacin and gentamicin was significantly lower than that of HA-MRSA(P<0.05).The PVL detection rate was not statistically different between the two groups.Conclusion:1.The MRSA infection is principally respiratory tract infection,followed by skin soft tissue infection,consistent with domestic and international reports.2.Molecular epidemicresults suggest that ST59-MRSA-IVa is the mainly genetype in CA-MRSA,and ST239-MRSA-III is principal genetype in HA-MRSA strains,consistent with the main domestic trend.Meanwhile,MRSA has been emerged hospital-community mutual transmission,suggesting the importance of monitoring MRSA molecular epidemiology and taking measures to control the infection and transmission.3.The resistance and virulence of MRSA strains in this hospital are serious.There is no strain resistant to quinupidine/dalofopine,linezolid,and vancomycin in this hospital.Clinical departments should pay more attention to monitor drug-resistant strains. |
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