探讨凝固酶阴性葡萄球菌阳性报警时间在儿童血流感染中的意义

Value of time to positivity of blood culture for coagulase-negative staphylococci in children with bloodstream infection

目的:探讨儿童血培养凝固酶阴性葡萄球菌(CoNS)的阳性报警时间(TTP)对血流感染与污染的鉴别诊断应用价值。方法:采用回顾性研究,收集本院2018年10月至2019年8月10720份住院患儿血培养中结果报告为凝固酶阴性葡萄球菌阳性的病人资料。根据相应的判断标准,分为CoNS感染组(154例)、CoNS污染组(113例),收集同时期的金黄色葡萄球菌作为阳性对照(SA组,37例)。绘制受试者工作特征(ROC)曲线,分析TTP对不同组别的鉴别诊断效能。结果:267株CoNS中以人型葡萄球菌(50.94%)、表皮葡萄球菌(34.46%)、溶血葡萄球菌(5.61%)为常见,感染组与污染组的构成无明显差异(P>0.05)。感染组各实验室指标均高于污染组,而TTP均值[19.5(17.4,22.4)]显著低于污染组TTP[30.1(23.1,43.8)],差异有统计学意义,P<0.01;与SA组TTP[17.1(12.4,25.2)]、其它各实验室指标比较差异均无统计学意义,P>0.05。ROC曲线分析CoNS感染组与污染组,曲线下面积AUC为0.836[95%CI(0.786~0.885)],P<0.01。当TTP最佳cut-off值为22.4 h时,区别CoNS感染与污染的灵敏度为0.796,特异性为0.734。结论:儿童血培养以阳性报警时间22.4 h为临界值,可有效的鉴别儿童凝固酶阴性葡萄球菌血流感染与污染。

Objective To determine the value of time to positivity(TTP)of blood culture for coagulase-negative staphylococcus(CoNS)in children in distinguishing bloodstream infection and contamination.Methods A retrospective study was conducted on data from 10720 children who stayed in our hospital between October 2018 and August 2019 and tested positive for coagulase-negative staphylococci by blood culture.According to corresponding judgment criteria,they were divided into the CoNS infection group(n=154)and CoNS contamination group(n=113).Contemporary samples of Staphylococcus aureus were collected as positive controls(SA group,n=37).Receiver operating characteristic(ROC)curve was generated to analyze the performance of TTP in distinguishing between different groups.Results Staphylococcus hominis(50.94%),Staphylococcus epidermidis(34.46%),and Staphylococcus hemolyticus(5.61%)were common species among the 267 CoNS strains.There was no significant difference in the composition of CoNS strains between the infection group and the contamination group(P>0.05).The infection group showed higher values of all laboratory indicators and significantly shorter TTP[19.5(17.4,22.4)vs 30.1(23.1,43.8)]compared with the contamination group(P<0.01),but did not differ statistically from the SA group in TTP[17.1(12.4,25.2)]and all laboratory indicators(P>0.05).ROC curve analysis showed that the area under the curve(AUC)was 0.836[95%CI(0.786-0.885)](P<0.01)for TTP in distinguishing the infection and contamination groups.Using an optimal cut-off of 22.4 h,the sensitivity and specificity of TTP in distinguishing between CoNS infection and contamination was 0.796 and 0.734,respectively.Conclusion A TTP cut-off of 22.4 h may well distinguish between bloodstream infection and contamination in blood culture for CoNS in children.