| Objective: Through the study of the strains isolated from the internal fixation of methicillin-resistant Staphylococcus aureus in chronic osteomyelitis after fracture internal fixation in our hospital,the drug resistance of the strains was analyzed,and the virulence genes of the strains were detected.The number of virulence genes carried by each strain and the expression of virulence genes were compared.To grasp the pathogenicity and clinical characteristics of patients with different methicillin-resistant Staphylococcus aureus infection,so as to provide help and guidance for clinical osteomyelitis prevention and targeted treatment.Methods: T The internal fixation devices of 30 inpatients in the Department of Orthopaedic Trauma of the 940 th Hospital of the Joint Logistics support Force of the Chinese people’s Liberation Army from May 2021 to February 2023 were collected.the strains were identified using a combination of traditional methods and mass spectrometry,and the initial screening experiment of methicillin-resistant Staphylococcus aureus was performed by the cefoxitin method,and the sensitivity analysis of commonly used clinical antibacterial drugs was performed by the K-B method,and primers were synthesized with reference to the literature After that,the strains were tested for leukocidin gene,toxic shock syndrome toxin gene,enterotoxin gene,hemolysin gene,fibrinogen agglutinin gene and fibrin-linked protein gene by quantitative real-time fluorescence polymerase chain reaction(Quantitative Realtime PCR,q PCR),and electrophoresis.The data such as the number of days of hospitalization,the number of strains of drug resistance,and other data were counted,and pearson correlation analysis was performed using SPSS22.0 software for clinical characteristic indexes and virulence gene expression.Results:(1)The positive rate of bacterial detection was up to 100% after the culture of 30 specimens by rolling plate method.(2)The drug sensitivity results showed that the total resistance rate of 30 methicillin-resistant Staphylococcus aureus strains to penicillin G and benzocillin was 100%,and the resistance rate to ciprofloxacin,cotrimoxazole,erythromycin,ciprofloxacin,clindamycin,gentamicin,tetracycline and moxifloxacin was between 20-98%,and no resistant strains to linezolid,vancomycin and tigecycline were found at present.(3)q PCR experiment results: 30 strains of methicillin-resistant Staphylococcus aureus virulence genes clf A,fnb A,sec gene detection rate was 100%,pvl and tst genes were detected,hla gene detection rate was96.6%.(4)Different strains of fnb A,clf A,sec,Hla,pvl and tst did not carry the same status and expression.(5)There was a positive correlation between the expression of virulence factors fnb A,clf A and hla and the number of hospitalization days,drug resistance,white blood cell count,neutrophil percentage,calcitoninogen,interleukin-6and blood sedimentation.There was a positive correlation between sec expression of virulence factor and 5 indicators,including hospitalization days,white blood cell count,interleukin-6,hematocrit,and drug resistance number.There was no correlation between sec expression and two indicators,namely neutrophil percentage and calcitoninogen.(6)The sec gene as an independent factor had a significant positive effect on the number of days of hospitalization.Conclusion:(1)the positive rate and sensitivity of bacterial culture on the surface of orthopedic internal fixation by rolling plate method are reliable.(2)different strains have different drug resistance to antibiotics,and show the trend of multiple drug resistance.For such patients,penicillin G,moxifloxacin,tetracycline and oxacillin should be avoided before microbial culture and drug sensitivity test.(3)the carrying situation and expression amount of virulence factors were different among different strains,and the gene expression levels of virulence factors fnb A,clf A,hla and sec were significantly correlated with clinical characteristics,indicating that the more virulence genes were carried,the higher the expression level was,the stronger the pathogenicity of the strains was.(4)sec gene could be used as an independent factor to have a positive effect on the days of hospitalization.The results showed that with the increase of virulence factor sec expression,the hospitalization days of patients also increased. |
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