Abstract: Objective　To analyze the significance on the bacterial distribution in blood culture and the positive alarm time in differentiating the pathogens and contaminated bacteria.   Methods　The retrospective analysis of 642 isolates for blood culture from July 2009 to December 2011 was performed to observe the bacterial distribution, and 148 possible contaminated bacteria were comprehensively analyzed with the clinical data. Results　Of the 642 positive isolates, 338(52.6%)were Gram-negative,280 (43.6%) were Gram-positive, and 24 (3.7%)were fungi. The 376 (58.6%) isolates were detected in<18 h,120 (18.7%) isolates were detected in 19-24 h,89 (13.9%) isolates were detected in 25-48 h, and 57 (8.8%) isolates were detected in＞48 h. Totally 111 of 148 isolates were identified to be contamination by reviewing the clinical data, and the contamination rate was 17.3%.All the contaminated bacteria were Gram-positive, and coagulase negative Staphylococcus was major. The 33 isolates were pathogens, and 4 isolates were indeterminable. The counts of contamination durning 19-24 h, 25-48 h and ＞48 h were 14 isolates, 40 isolates and 57 isolates with positive alarm time ＞ 18 h, respectively. Conclusions　The bacterial distribution in blood culture is wide in this area, and the contamination rate is high. The pathogens and contaminated bacteria can initially be differentiated by the clinical data and other auxiliary examination combining with the positive alarm time according to certain evaluation standard.

Key words: Blood culture, Positive alarm time, Pathogen, Contaminated bacterium