外科发热患者静脉血中大肠埃希菌DNA实时定量PCR检测与体征及血细胞计数的相关性

目的 定量检测外科发热患者静脉血中大肠埃希菌DNA含量，研究其与体征及皿细胞计数之间的相关性，并比较不同检测方法对血中大肠埃希菌的阳性检出率的差异。方法 以实时定量PCR（RQ-PCR）定量检测40份健康人静脉血标本，确定临床阳性检测限。31例发热患者共72份血标本同时进行常规细菌培养及大肠埃希菌DNA定量检测，比较两种检测方法对血中大肠埃希菌的阳性检出率的差异，两个取血时间点间大肠埃希菌DNA含量的变化，并计算大肠埃希菌DNA含量与体温、心率、白细胞计数、中性粒细胞及淋巴细胞百分比之间的相关性。结果 RQ-PCR定量检测大肠埃希菌DNA阳性率为52．78％（38／72），显著高于细菌培养阳性率2．78％（2／72）（P=0．000）。同一患者两个时间点血标本检测结果显示，静脉血中大肠埃希菌DNA在2～6小时内的升降变化达10～20倍。血中大肠埃希菌DNA含量与体温和心率之间均显著相关（P=0．000），相关程度中度密切（，值分别为0．565和0．546），与白细胞计数、中性粒细胞及淋巴细胞百分比之间无显著相关关系。结论 RQ-PCR检测外科发热患者静脉血中大肠埃希菌阳性率远高于血培养。血中大肠埃希菌DNA拷贝数变化速度较快。血细胞计数不能很好反映血中大肠埃希菌的含量，而体温心率的影响因素较多，因此RQ-PCR能更及时准确反映大肠埃希菌血症的严重程度，有助于对肠屏障损伤导致肠道细菌移位的动态程度或后果进行评估。

Correlations of Real-time Quantitative PCR Determined Escherichia coli DNA in Venous Blood with Vital Signs and Blood Cell Count in Febrile Surgical Patients

Objective To quantitatively determine the venous blood Escherichia coli (E.coli) load in febrile surgical patients and study the correlations between E.coli load and vital signs and blood cell count,and to compare the difference of E.coli positive rates determined by different methods. Methods E.coli load of the venous blood samples from 40 healthy volunteers were measured quantitatively by real-time quantitative PCR (RQ-PCR) to determine the cut off value for reporting E.coli positive status. Seventy-two blood samples from 31 patients were collected for E.coli detection by RQ-PCR and bacterial culture. The difference of E.coli positive rates determined by two methods and the E.coli load changes between two time points of blood sampling were compared. The correlations between E.coli load and body temperature, heart rate, white blood cell count, and percentages of leukocyte and lymphocyte were then analyzed. Results The E.coli positive rate determined by RQ-PCR was significantly higher than that by bacterial culture (P= 0.000). The E.coli DNA load changed 10-20 folds in patients' venous blood within 2-6 hours. The venous E.coli DNA load moderately significantly correlated with both body temperature and heart rate (r values were 0.565, 0.546,respectively, P=0.000), but not with white blood cell count, percentages of leukocyte and lymphocyte. Conclusions The E.coli positive rate determined by RQ-PCR is much higher than that measured by bacterial culture. The E.coli DNA copies in the blood change rapidly. Routine blood cell count may not accurately reflect the blood E.coli load. Body temperature and heart rate may be difficult to predict the venous E.coli load because of various impact factors. RQ-PCR can accurately determine the blood E.coli load and quickly evaluate the bacterial translocation resulted from gut barrier damage.