Abstract

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (TOF MS) is now widely used to detect pathogens in clinical settings in the world. However, there are some critical points, including polymicrobial samples handling and the kinds of lysis buffer in the protocol of direct identification of specific pathogens from blood culture samples.

The infecting bacteria were not correctly identified in many polymicrobial samples although all monomicrobial samples were detected by TOF MS, however, if the culture ratio were changed, two pathogens were correctly detected.

Furthermore, in the effects of adding lysis buffer in the TOF MS method to directly detect bacteria from three blood culture systems, three types of blood culture broths showed similar detection efficiencies without lysis buffer use and most of gram negative rods were efficiently detected in all broths when lysis buffer was used. However, Streptococcus pneumoniae was not detected in BD broth when lysis buffer was added. Furthermore, Haemophilus influenzae and Bacteroides fragilis were not detected in all three systems when lysis buffer was used.

These results suggested that TOF-MS is a strong tool for the rapid and correct detection of pathogens from blood culture samples, although results need to be carefully checked when handling known or suspected polymicrobial samples, and optimization of blood culture system and lysis buffer dependent on the pathogens is necessary according to each pathogen for direct identification by TOF MS methods.

Keywords: Blood cultures broth; Lysis buffer; Polymicrobial samples