| Part I Incidence,clinical characteristics and drug resistance of Staphylococcus aureus bloodstream infectionObjective:To analyze the clinical characteristics and the changes of drug resistance of Staphylococcus aureus(SA)patients with bloodstream infection in a hospital,so as to provide reference for the rational use of antimicrobial agent in clinical SA bloodstream infection.Methods:The drug sensitivity data and clinical data of inpatients with SA bloodstream infection in a hospital from January 2012 to December 2019 were collected(including general information of patients,basic diseases,invasive operation and prognosis,etc.).Cases under 18 years old and key data missing were deleted and 130 cases were included.The patients were divided into two groups according to the year: group 2012～2015(n=43)and group 2016～2019(n=87),to analyzed the clinical characteristics of patients with SA bloodstream infection,the changes of SA resistance and the detection of methicillin-resistant strain(MRSA)in the past eight years.The data were processed and statistically analyzed by SPSS 21.0 software.Results:1.Incidence of SA bloodstream infectionA total of 406217 adult inpatients were admitted to our hospital in the past eight years,the incidence of SA bloodstream infection was 3.2/10000.The incidence of bloodstream infection increased from 1.8/10000 in 2012 to3.0/10000 in 2019.Chi-square trend analysis showed that the incidence of bloodstream infection increased significantly(P<0.05).2.Clinical characteristics of SA bloodstream infectionAmong the 130 patients with SA bloodstream infection,there were 88males(67.7%)and 42 females(32.3%),with an average age of 61.4±17.4years.These included 77 cases(59.2%)of hospital-acquired infections and 53cases(40.8%)of community-acquired infections.The patients were mainly distributed in intensive care unit(ICU)(40 cases,30.8%),nephrology(36cases,27.7%),respiratory department(6 cases,4.6%)and endocrinology department(6 cases,4.6%).114 patients(87.7%)had underlying diseases,98 cases(75.4%)were complicated with two or more underlying diseases among them.Cardiovascular disease(82 cases,63.1%),kidney disease(56 cases,43.1%)and diabetes(51 cases,39.2%)were the most common.100 patients(76.9%)underwent invasive procedures before infection,including indwelling venous catheterization in 73 cases(56.2%),retained catheterization in 72 cases(55.4%)and mechanical ventilation in 24 cases(18.5%),among them,47(36.2%)underwent two or more invasive procedures during hospitalization.The main sources of infection were pulmonary infection in 59 cases(45.4%),hemodialysis catheter infection in 38 cases(29.2%)and skin and soft tissue infection in 35 cases(26.9%).Infection of unknown origin in 7 cases(5.4%),and two or more site infections were found in 39 cases(30.0%).Among the130 patients,the 28-day prognosis was good in 96 cases(73.8%)and poor in34 cases(26.2%),of which 14 cases died in hospital(10.8%).3.Drug resistance of SA to common antimicrobialsIn the past eight years,SA was 100.0% sensitive to vancomycin,linezolid and tegacycline.The resistance rates of oxacillin,gentamicin,levofloxacin,ciprofloxacin and moxifloxacin were lower than 30.0%,the resistance rates of penicillin,erythromycin and clindamycin were more than 60.0%.Compared with 2012～2015,the resistance rate of SA to common antibiotics(except oxacillin and quinolones)showed a downward trend in 2016～2019,but only penicillin,erythromycin and gentamicin had significant difference.The detection rate of MRSA was 22.3%.With the change of year,the detection rate of MRSA increased from 18.6% in 2012 to 24.1% in 2019,but the difference was not statistically significant.Conclusions:1.In the past eight years,the incidence of SA bloodstream infection in this hospital remained at 1.8/10000～4.1/10000,and showed a significant upward trend with the change of the year.2.Most of the patients with SA bloodstream infection were male,mainly admitted in ICU and nephrology.Most of the patients were complicated with underlying diseases and had a high proportion of invasive operations.the main sources of infection were lung and hemodialysis catheter infection.3.In the past eight years,SA was completely sensitive to vancomycin,linezolid and tegacycline.The resistance rate to oxacillin,gentamicin,levofloxacin,ciprofloxacin and moxifloxacin was less than 30.0%,and the resistance rate to penicillin,erythromycin and clindamycin was more than60.0%.Compared with 2012～2015,the resistance rate of SA to penicillin,erythromycin and gentamicin decreased significantly from 2016～2019,while the detection rate of MRSA had no significant change.Part II Risk factors of MRSA bloodstream infection and preliminary establishment and evaluation of infection risk prediction modelObjective:1.To analyze the risk factors of MRSA bloodstream infection and its influence on the prognosis of patients,in order to strengthen the prevention and treatment of MRSA infection.2.To establish a risk prediction model of MRSA bloodstream infection in our hospital and evaluate the clinical value of the model.Methods:1.The clinical data of 150 patients with SA bloodstream infection in a hospital from January 2012 to December 2020 were collected.The patients admitted from January 2012 to December 2019 were taken as the model group(n=130),and the patients admitted from January to December 2020 as the verification group(n=20).According to whether the pathogens detected in the model group were resistant to methicillin,divide the model group into two groups: methicillin resistant group(MRSA group,n=29)and methicillin sensitive(MSSA)group(MSSA group,n=101).To compare the difference of clinical characteristics between the two groups of patients,and analyze the risk factors of MRSA bloodstream infection by Logistic regression.According to the partial regression coefficient(β value)of independent risk factors,establish a regression equation,MRSA bloodstream infection risk prediction model= β0+risk factor 1×β1+risk factor 2×β2+...+risk factor X×βX,the model was applied to the patients in the model group for Hosmer-Lemeshow test(P>0.05).The accuracy,sensitivity and specificity of the model were evaluated by ROC curve,and obtain the critical value of MRSA infection.Then apply the model to the verification group to observe the coincidence between the predicted results of the model and the actual situation.2.17 patients in the verification group who had received empirical medication before the diagnosis of SA bloodstream infection were divided into two groups according to whether the empirical medication was consistent with the model: appropriate experience in anti-infective therapy group(n=8)and inappropriate experience in anti-infective therapy group(n=9).The clinical effects of the model were evaluated from three aspects: 28-day prognosis,hospitalization cost and hospitalization time.Results:1.Risk factors of MRSA bloodstream infectionLogistic regression analysis showed that admission to ICU(OR=5.595,95%CI: 2.073～15.100,P=0.001),hospital acquired infection(OR=4.044,95%CI: 1.311～12.471,P=0.015),infection source≥two sites(OR=3.421,95%CI: 1.225～9.550,P=0.019)and history of antimicrobial use within 2weeks before diagnosis(OR=3.499,95%CI: 1.110～11.028,P=0.033)were independent risk factors for MRSA bloodstream infection.In the use of antimicrobials,the use of third and fourth generation cephalosporins within 2weeks before diagnosis(OR=3.120,95%CI: 1.124～8.661,P=0.029)is associated with MRSA bloodstream infection.2.Construction of risk prediction model for MRSA bloodstream infectionThe regression equation for predicting the risk of MRSA bloodstream infection=-1.427+admission to ICU×1.722+hospital acquired infection×1.397+infection source≥two sites×1.230+history of antimicrobial use within 2 weeks before diagnosis×1.252.By Hosmer-Lemeshow test,P=0.566>0.05,the goodness of fit is good.The area under the ROC curve(AUC)=0.835(95%CI: 0.762～0.908,P<0.001),the discriminant sensitivity of the model is 72.4%,the specificity is 79.2%,and the critical value of MRSA infection is 11.5.The overall accuracy,sensitivity and specificity of the verification group under the model were 80.0%,66.7% and 85.7%,respectively.3.Evaluation of clinical effect of MRSA bloodstream infection risk prediction model.Compared with the clinical prognosis of the inappropriate experience in anti-infective therapy group,the proportion of poor prognosis,hospital death,hospitalization cost and hospitalization time of the appropriate experience in anti-infective therapy were lower than those of the inappropriate experience in anti-infective therapy.there was significant difference in hospitalization cost and length of stay between the two groups(P<0.05).Conclusion:1.Admission to ICU,hospital acquired infection,more than two sources of infection and history of use of antibiotics within 2 weeks before diagnosis were independent risk factors for MRSA bloodstream infection,among which the use of third or fourth generation cephalosporins within 2 weeks was associated with MRSA bloodstream infection.2.The risk prediction model of MRSA bloodstream infection established in this study has a critical value of 11.5,which has a high overall effective rate and can be used to predict MRSA bloodstream infection clinically.3.Using the MRSA risk prediction model established in this study,targeted selection of antibiotics can effectively reduce the hospitalization costs of patients and shorten the length of stay of patients. |
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