预培养对血液常见感染菌血培养阳性报警时间的影响

Effect of preincubation on time to detection of blood culture of common blood infectious bacteria

目的探究不同预培养条件对血液常见感染菌血培养阳性报警时间的影响,指导临床血培养标本合理运输与接收。方法将金黄色葡萄球菌、大肠埃希菌和铜绿假单胞菌三种血液常见感染菌配成10CFU/ml和100CFU/ml浓度菌液,分别注入标准需氧和厌氧血培养瓶,人工模拟构建阳性血流感染标本。血培养瓶置于25℃和37℃预培养0、2、4、8、12、24h立即放入BacT/Alert 3D血培养仪,记录、分析阳性报警时间。结果金黄色葡萄球菌、大肠杆菌在25℃预培养8h、37℃预培养4h阳性报警时间均明显缩短,铜绿假单胞菌在25℃预培养12h、37℃预培养8h阳性报警时间明显缩短,与未预培养组(0h)相比差异均有统计学意义(P<0.05)。不同菌落数(菌液浓度)和不同培养瓶类型(需氧或厌氧)间阳性报警时间差异不明显(P>0.05)。铜绿假单胞菌25℃和37℃预培养24hBacT/Alert 3D血培养仪均报告阴性(假阴性)。结论从实验结果得出,三种实验菌的阳性报警时间主要受预培养温度和时间的影响,与注入菌落数及培养瓶类型相关性不大;不能及时放入血培养系统的标本应置于37℃预培养,预培养时间不能超过24h。

Objective To explore the effect of preincubation conditions on the time to detection （TTD） of blood culture of common blood infectious bacteria and provide evidence for shipping and handling the clinical blood culture specimens reasonably. Methods In order to mimic blood infection specimens, Staphylococcus aureus （ S. aureus ） , Escherichia coli （ E. coli ） and Pseudomonas aeruginosa （ P. aeruginosa ） at 10 and 100 CFU/ml were inoculated into standard aerobic or anaerobic blood culture bottles, and then were preineubated at 25℃ or 37℃ for 0, 2, 4, 8, 12 or 24h. TTD was monitored using BacT/Alert 3D sys- tem. Results Compared with the groups without preincubation, TTD was significantly shortened following preincubation for 8 hr at 25℃ and 4 hr at 37℃ for S. aureus and E. coli, as well as for 12 hr at 25℃ and 8 hr at 37℃ for P. aeruginosa （P 〈 0.05）. No statistical differences in TTD were observed between different bacterial concentrations （P 〉 0.05）, or between aer- obic and anaerobic incubation groups（P 〉0.05）. The BacT/Alert 3D system reported false-negative results for P. aeruginosafollowing preincubation for 24 hr at 25℃ or 37℃. Conclusions T-FD of Staphylococcus aureus, Escherichia coli and Pseud- omortas aeruginosa in blood specimens is mainly affected by temperature and duration of preincubation rather than by input amount of CFU or type of blood culture bottle. So blood specimens that can＇ t be put in BacT/Alert 3D system in time should be preincubated at 37℃ , but for no more than 24h.