| Objective:1.Collect basic clinical information of patients with methicillin-resistant Staphylococcus aureus(MRSA)select from skin and soft tissue infections(SSTIs)to analyze their clinical characteristics and drug sensitivity.2.To analysis the drug sensitivity of MRSA clinical isolates in Jiangxi province to fusidic acid,and clarify the genotype of the fusidic acid-resistant MRSA strains.3.Understand the molecular characteristics(genotyping,virulence genes and drug resistance genes)and main clonotypes of MRSA strains isolated from SSTIs in Jiangxi,and explore the association of genotyping,virulence genes,drug resistance genes and drug resistance phenotypes.Methods:Collected cases of SSTIs patients in 9 different hospitals in Jiangxi,and reserved clinical information of patients.Bacterial identification and drug susceptibility test of each MRSA isolates was performed,and using broth dilution method to detect the minimum inhibitory concentration(MIC value)of all isolated MRSA strains to fusidic acid,and detect spa typing and MLST typing of MRSA strains resistant to fusidic acid(FA-MRSA).Screened 60 MRSA strains from patients with SSTIs,analyzed the clinical characteristics of MRSA infection,and genotyping,virulence gene eg pvl、hla、hlb、hld、sea、seb、tst and drug resistance gene aac(6’)/aph(2’’)、aph(3’)-Ⅲ、ermA、ermB、ermC、tetM were detected on the MRSA.Results:1.We cultured 175 MRSA isolate from 9 hospitais totally,After PCR amplification,all mecA genes were positive,and 10 strains of MRSA resistant to fusidic acid were screened out,with a resistance rate of 5.7%,and all MICs are ≧8μg/mL.A total of three genotypes have been detected in FA-MRSA.Among them,5strains of MRSA genotype were ST239-MRSA-t4549,MICs at 8-16μg/mL,which showed low concentration resistance to fusidic acid.In addition,three strains ofST5-MRSA-t2460 and two strains of ST5-MRSA-t7130 had higher MIC values,both> 64μg/mL,which met the high concentration of fusidic acid resistance standards.2.Screened 60 MRSA strains from patients with SSTIs resulted by MRSA clinical isolates.Statistics of patients’ clinical information showed that 61.7% of infections occur in the community,and 24.3%(9/37)of these patients are underage.SSTIs-derived MRSA strains are 100% resistant to β-lactam antibiotics,these isolates are all sensitive to tigecycline and vancomycin,and the total drug resistance was93.3%for erythromycin,and 88.9% for clindamycin,the resistance rate to other antibacterial drugs is less than 40%.The drug resistance rate of MRSA isolated from patients with SSTIs to clindamycin and erythromycin was significantly higher than that of MRSA strains separated from other types of infection(P <0.05),while the drug resistance rate to levofloxacin and moxifloxacin was significantly lower than that of MRSA strains that derived other types of infection(P <0.05).3.The genotyping of MRSA strains isolated from patients with skin and soft tissue infections was detected.A total of 21 spa types were detected,of which the type t437 was the most common,with a total of 18 strains(29.5%),followed by 6strains of type t114.MLST typing was performed on the selected MRSA strains,and a total of 12 STs were detected,including a new clone type,ST59(22/60,36.7%)was the most common sequence type,followed by ST239(11 / 60,18.3%),ST59-MRSA-t437 was the superiority clonotype in the included research strain(14/60,23.3%).4.The virulence genes and drug resistance genes of the included strains were amplified,and the results showed that the pvl positive rate was 20% among the SSTIs-derived MRSA strains,of which 66.7% pvl positive MRSA strains belonged to Spa-t437 type.The positive rates of hla,hlb,hld,sea,seb and tst were 70.0%、60.0%、71.7%、15.0%、10.0% and 8.3%.The aminoglycoside-related drug resistance genes aac(6 ’)/ aph(2’ ’),aph(3’)-Ⅲ positive rate was 18.3% and 41.7 %,The positive rates of macrolide-related resistance genes ermA,ermB,ermC were 8.3%,53.3% and28.3%,and the positive rates of tetracycline-related resistance genes tetM were 8.3%,2 strains of MRSA did not detect any of the virulence genes and drug resistance genesabove.Conclusion:1.The main genotypes of MRSA resistant to fusidic acid are genotypes ST239-MRSA-t4549 and ST5-MRSA-t2460.Fusidic acid is still an effective drug for clinical treatment of MRSA,because the resistance rate to fusidic acid of clinical isolates of MRSA is low in Jiangxi province.2.The MRSA isolated in patients with SSTIs is mainly come from community.The resistance rate of MRSA strains from SSTIs to erythromycin and clindamycin was higher than that of MRSA strains from other infection sources.No MRSA strains resistant to vancomycin and teicoplanin were found.3.ST59-MRSA-t437 is the dominant clone that causes SSTIs,and has strong virulence.The risk of carrying the pvl gene in type t437 is significantly higher than that of other types of MRSA.The hemolysin gene is the most common virulence factor in MRSA,ST5-MRSA-t2460 strain is highly toxic and has low sensitivity to antibacterial drugs. |
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