Abstract:

Objective To study the application of Gram staining and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF MS） in the rapid identification of pathogen kinds in children's positive blood culture，and to provide a rapid and accurate laboratory reference for children's bloodstream infection. Methods The positive aerobic blood culture bottles of children submitted for clinical examination in Beijing Children's Hospital Affiliated to Capital Medical University from February 2019 to October 2020 were collected. Gram staining microscopy，rapid identification of MALDI-TOF MS and culture were carried out. Based on the identification results after culture，the effect of Gram staining and rapid identification of MALDI-TOF MS was evaluated. Results A total of 166 positive samples of children's aerobic blood culture were collected，of which 97.6% （162/166） were single bacteria，and 2.4%（4/166） were multiple bacteria. According to the identification results after culture，the coincidence rate of Gram staining microscopy in 162 single bacterium samples was 97.5%（158/162），of which the coincidence rate of Gram-positive bacteria was 97.9%（93/95），Gram-negative bacteria was 96.8%（61/63），and the coincidence rate of yeast like fungi was 100.0%（4/4）. The coincidence rate of rapid identification by MALDI-TOF MS was 85.2%（138/162），including 81.1% （77/95） of Gram-positive bacteria，92.1%（58/63） of Gram-negative bacteria and 75.0%（3/4） of yeast like fungi. Among the 4 2-kind bacteria samples，the results of Gram staining microscopy were consistent with those after culture，and only one of them could be identified by MALDI-TOF MS. The coincidence rate of rapid identification of Gram-negative bacteria by MALDI-TOF MS was higher than that of Gram-positive bacteria（P>0.05）. When time to positivity（TTP）< 21 h，the coincidence rate of MALDI-TOF MS was higher，especially for Gram-negative bacteria（P<0.05）. Conclusions Gram staining and MALDI-TOF MS can rapidly identify the pathogens in children's positive blood culture in a short time，so as to provide a rapid and accurate laboratory reference for clinical diagnosis and treatment of children's bloodstream infection，and to reduce the hospitalization cost and mortality of bloodstream infection in children.

Key words: Gram staining, Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Rapid identification, Children, Blood culture