【作者】 郑辉；

【导师】 夏大静；

【作者基本信息】 浙江大学 ， 免疫学， 2016， 硕士

【摘要】 血流感染包括菌血症和败血症,是由于致病菌进入血液后生长繁殖并释放毒素和代谢产物,引起急性重症感染性疾病,其发病率和致死率都较高,危害极大。降钙素原(procalcitonin,PCT)是降钙素的前体,在健康人的外周血中含量很低,当细菌感染时,血浆中的PCT会明显升高。近年来,国内外关于PCT的研究已有很多,但对其临床应用价值尚存争议,本研究旨在分析血流感染患者PCT水平在不同细菌种类、多重耐药菌株及常见致病菌多重耐药时的水平特征,以探索PCT检测在血流感染早期诊断与鉴别诊断中的实际临床意义。选取医院2013年1月至2014年12月疑似发生血流感染的住院患者,经筛选甄别后有1106例患者纳入研究,采集血培养的同时检测血浆PCT水平;并从中随机选择180例多重耐药菌株感染患者进行比较分析。血培养用BacT/Alert3D480血培养仪,病原菌鉴定使用法国梅里埃公司生产的VitekⅡ微生物全自动鉴定;VitekⅡ仪器未鉴定出的细菌使用德国Bruker microflex LT时间飞行质谱仪鉴定。血浆PCT的测定采用电化学发光法,德国罗氏公司生产的ROCHE E601全自动免疫发光分析仪进行检测。采用SPSS 17.0统计软件进行统计分析,使用WHONET5.6细菌耐药监测软件分析耐药菌株。非正态分布数据用中位数(四分位数)[M(P25-P75)]表示。各组间PCT值的差异比较采用Mann-Whitney U检验;统计结果P<0.05视为差异有统计学意义;绘制受试者工作特征曲线(ROC曲线)评价血浆PCT水平鉴别血流感染致病菌种类的诊断性能及多重耐药菌株感染的诊断效能,计算约登指数找出CUTOFF值。筛选后共有临床病例1106例,其中男性704例,女性402例,年龄分布为8～97岁,平均年龄57.30±16.57岁;血培养结果阳性的有507例(53%的病例来源于ICU病区)。其中G+菌296例,构成比为58.38%,G-菌141例构成比为27.81%,真菌17例,构成比为3.35%。以血浆PCT>0.5μg/L为临界值,G-细菌感染组的PCT阳性率为62.41%,G+细菌感染组阳性率为36.82%,真菌感染感染组阳性率为47.06%,混合感染时PCT阳性率高达98.04%,表明混合感染时PCT阳性率明显高于单一菌株感染(U =5137.5,P=0.001)。血培养阳性组与血培养阴性组比较PCT水平差异有统计学意义(U=71057.5,P=0.000);混合感染组与G+细菌感染组比较PCT水平差异有统计学意义(U =5137.5,P =0.001)。507例血培养阳性结果中,G-菌感染患者PCT水平为0.95(0.28-7.57)μg/L,G+菌感染患者PCT水平为0.26(0.09-1.18)μg/L;真菌阳性结果中以白色念珠菌为主,其中5例为混合感染。G-菌感染者PCT水平高于G+菌组,两者比较差异有统计学意义(U=12817.50,P=0.000);G-细菌感染组与真菌感染组比较PCT水平差异无统计学意义(U=901.00,P=0.095);G+菌组与真菌感染组比较PCT水平差异无统计学意义(U=2398.500,P=0.060)。上述结果表明血培养阳性组的PCT值明显高于血培养阴性组(U=94131.50,P=0.000),提示PCT水平可以用于早期预测患者是否发生血流感染。多重耐药分析显示:血流感染多重耐药(Multidrug resistant,MDR)菌株患者的PCT阳性率为66.67%,与非MDR菌株患者的PCT水平差异有统计学意义(U=9666.500,P =0.000),血流感染泛耐药(Extensively drug-resistant,XDR)菌株患者的PCT阳性率为69.74%,与非XDR菌株患者的PCT水平差异有统计学意义(U=9046.000,P=0.000)。6种常见的致病菌鲍曼不动杆菌(aba)、大肠埃希菌(eco)、屎肠球菌(efm)、肺炎克雷伯菌(kpn)、铜绿假单胞菌(pae)及金黄色葡萄球菌(sau)感染患者的PCT阳性率分别为64.56%、57.14%、57.14%、71.43%、83.33%和 54.55%。经Kruskal-Wallis检验发现,各种致病菌间的PCT水平差异有统计学意义(χ2=31.840,P=0.000)。抗菌治疗过程中,前7天多重耐药菌株感染患者PCT水平变化与非多重耐药菌株感染患者PCT水平比较差异有统计学意义(U=4053.500,P =0.000);在抗菌有效治疗7天后多重耐药菌株感染患者PCT水平变化与非多重耐药菌株感染患者PCT水平比较差异无统计学意义(U=10362.000,P=0.845)。当CUTOFF值为1.52μg/L时,血浆PCT水平区分诊断多重耐药菌株所致血流感染的灵敏度为41.20%,特异度为93.90%,ROC曲线下面积为0.71。研究结论:G-细菌感染时的PCT水平高于G+细菌,混合感染的PCT阳性率明显高于单一菌株感染。患者发生血流感染时,PCT水平阳性结果不适用于预测病原体种类。当PCT低于0.25μg/L可排除血流感染。血流感染患者PCT≥1.52μng/L时,排除其它升高PCT的病因后可早期预测多重耐药菌株感染的可能。应用PCT指导临床对多重耐药菌株感染患者的抗菌治疗是积极可行的。更多还原

【Abstract】 Bloodstream infections include bacteremia and septicemia,had high incidence and mortality rates,are the results of releasing toxins and metabolites from pathogenic bacteria into the blood.Procalcitonin(PCT),a precursor of calcitonin,has a low concentration in the peripheral blood of healthy individuals.However,as bacterial infection occurs,the level of PCT in plasma will increase significantly.Currently,reports regarding PCT have been increased significantly,but the value of its clinical application remains controversial.The purpose of this study was to evaluate the levels of PCT in patients with bloodstream infection in different bacterial species including multidrug resistant strains and some common pathogenic bacteria.From January 2013 to December 2014,we recruited 1106 patients with bloodstream infection for this study.We measured the PCT level in plasma and then randomly selected 180 samples from patients with multiple drug resistant.The BacT/Alert3D480 blood culture system was used for blood culture,Vitek II automated microbial was applied to identify the bacteria(French bioMerieux company);whereas the unidentified bacteria was assessed by the time-of-flight mass spectrometry(German Bruker MicroFlex LT).The level of PCT in plasma was determined by the electrochemical luminescence method(ROCHE E601 German).Statistical analysis was performed using SPSS 17.0 software.Moreover,the drug resistant strains were identified by employing the WHONET 5.6 bacterial drug resistance monitoring software.Median(four quantile)[M(P25-P75)]for non-normal distribution data.Mann-Whitney U test was used to compare the difference of PCT values between the groups.The P<0.05 was considered as statistically significant.We also draw the receiver operating characteristic(ROC)curve to evaluate the diagnostic performance of plasma PCT level to identify the type of pathogenic bacteria in blood flow infection,and its diagnostic efficiency of multidrug resistant strains infection.Among these 1106 patients,there are 704 male,402 female,aged between 8 to 97 years,with an average of 57.30±16.57 years.In addition,there are 507 patients from 1106 cases with positive results of blood culture(53%from ICU).296 cases are Gram positive(G+)bacteria(58.38%),while there are 141 cases with Gram negative(G’)(27.81%).17 cases were Fungi(3.35%).The positive rate of plasma PCT in patients under G" bacterial infection was 62.41%(CUTOFF value:0.5μg/L for PCT).The positive rate of plasma PCT in patients carrying G+ bacterial and fungal infections were 36.82%and 47.06%,respectively.However,when there are two kinds of bacterial infection,the positive rate of PCT reached the highest(98.04%).Notably,the PCT levels in positive blood culture group were significantly higher when compared with blood culture negative group(U=71057.5,P =0.000).Significant difference in PCT levels were observed between the mixed infection group and the G+ bacterial infection group(U=5137.5,P=0.001).Among these 507 blood culture positive samples,PCT levels in patients with G-bacterial infection were 0.95(0.28-7.57)μg/L,PCT levels in patients with G+ bacterial infection were 0.26(0.09-1.18)μg/L.Fungal positive results were almost Candida albicans,of which 5 cases were mixed infection.Furthermore,the levels of PCT in G-bacteria infected patients were higher than those in G+ bacteria infected group(U=12817.50,P=0.000).But there was no significant difference in the levels of PCT between the either G+ or G-bacterial infection groups and the fungal infection group(P>0.05).The results of this study showed that the PCT value of the blood culture positive group was significantly higher than that of the blood culture negative group(U=94131.50,P==0.000),suggesting that PCT can be used as a biomarker for patients with bloodstream infections.Multiple drug resistance(MDR)analysis showed that the positive rate of PCT in patients with MDR bacterial infection was 66.67%,when compared with non MDR bacterial infection(U=9666.500,P=0.000).The positive rate of PCT in patients with bloodstream XDR bacterial infection was 69.74%,when compared with non-XDR bacterial infection(U= 9046.000,P = 0.000).Positive rate of PCT in 6 common pathogenic bacterium including Acinetobacter Bauman(aba),Escherichia coli(eco),Enterococcus faecium(efm),Klebsiella pneumoniae(kpn),Pseudomonas aeruginosa(pae),Staphylococcus aureus(sau)infection were 64.56%,57.14%,57.14%,71.43%,83.33%and 54.55%,respectively(χ2=31.840,P=0.000)· In the course of antimicrobial therapy,within the previous 7 days,there were significant differences in the levels of PCT in patients with MDR strains of infection and the PCT levels in the patients with non-MDR strains(U=4053.500,P=0.000).But no significant difference was observed after 7 days of antimicrobial therapy(U=10362.000,P=0.845).When the CUTOFF of PCT level was 1.52μg/L,the specificity was 41.20%,and the specificity was 93.90%,and the area under the ROC curve was 0.71.Research conclusion:The PCT level of G" bacterial infection was higher than that of G+ bacteria,and the positive rate of ’mixed infection was significantly higher than that of single type of bacterial infection.The positive results of PCT levels were not applicable to predict the types of pathogens in patients with bloodstream infection.PCT concentration less than 0.25μg/L should be careful to exclude bloodstream infections.While the PCT level more than 1.52μg/L in patients under bloodstream infection,could be useful for early prediction the infection of MDR strains after the exclusion of other causes of PCT secretion.It is positive and feasible to use PCT to guide clinical treatment of patients with MDR strains of infection.更多还原