Abstract:

Objective To study the role of time to positive（TTP） of blood culturing in preliminary identification of microbial species and distinguishing between pathogenic bacteria and contaminated bacteria,and to provide a reference for early clinical warning and rational drug use. Methods Totally,534 positive and non-repetitive isolates from bloodstream infection（BSI） patients in Inner Mongolia Autonomous Region People's Hospital from 2017 to 2020 were analyzed. A comprehensive analysis was conducted combined with clinical data. Results Among the 534 isolates from blood culturing,323 isolates（60.5%） were determined with TTP≤1 d,454 isolates（85.0%） were determined with TTP≤2 d,and 513 isolates（96.0%） were determined with TTP≤3 d. The median alarm times of positive blood culturing were different,from the fastest to the slowest which were Enterobacteriaceae（0.57 d）,Streptococcus（0.68 d）,non-fermentative bacterium（0.71 d）,Enterococcus（0.72 d）,Staphylococcus（1.36 d）,yeast（1.98 d） and Brucella melitensis（2.75 d）. There was no statistical significance between Enterobacteriaceae TTP and non-fermentative bacterium TTP,Streptococcus TTP（P>0.05）,but there was statistical significance between Enterobacteriaceae TTP and Enterococcus,Staphylococcus,yeast and Brucella melitensis（P<0.05）. The determination rate of contaminated bacteria in 534 isolates of blood culturing was 18.5%（99 isolates）,and the determination rates of contaminated bacteria were 15.2% in 1 d,46.5% in 1-2 d,26.2% in 2-3 d and 12.1% in >3 d. The TTP≥1 d of suspicious contaminated bacteria accounted for 84.8%. Coagulase-negative Staphylococcus（59.6%） and Gram-positive bacilli（9.1%） were the predominant bacteria in contaminated bacteria. The TTP between pathogenic bacteria and contaminated bacteria had statistical significance（P<0.05）. Conclusions Pathogenic bacteria and their complex distribution in BSI patients can be preliminarily predicted according to TTP,pathogenic bacteria and contaminated bacteria can be distinguished,and drugs can be used rationally.

Key words: Blood culturing, Time to positive, Pathogenic bacterium, Contaminated bacterium, Determination rate