Early identification of microorganisms in blood culture prior to the detection of a positive signal in the BACTEC FX system using matrix-assisted laser desorption/ionization–time of flight mass spectrometry
Ming-Cheng Wang, Wei-Hung Lin, Jing-Jou Yan, Hsin-Yi Fang, Te-Hui Kuo, Chin-Chung Tseng, Jiunn-Jong Wu
Received: June 30, 2013 Revised: October 14, 2013 Accepted: October 15, 2013
Corresponding author. Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Number 1 University Road, Tainan 70101, Taiwan.
Background and purpose:
Matrix-assisted laser desorption/ionization–time of flight mass spectrometry (MALDI-TOF MS) is a valuable method for rapid identification of blood stream infection (BSI) pathogens. Integration of MALDI-TOF MS and blood culture system can speed the identification of causative BSI microorganisms.
We investigated the minimal microorganism concentrations of common BSI pathogens required for positive blood culture using BACTEC FX and for positive identification using MALDI-TOF MS. The time to detection with positive BACTEC FX and minimal incubation time with positive MALDI-TOF MS identification were determined for earlier identification of common BSI pathogens.
The minimal microorganism concentrations required for positive blood culture using BACTEC FX were >107–108 colony forming units/mL for most of the BSI pathogens. The minimal microorganism concentrations required for identification using MALDI-TOF MS were > 107 colony forming units/mL. Using simulated BSI models, one can obtain enough bacterial concentration from blood culture bottles for successful identification of five common Gram-positive and Gram-negative bacteria using MALDI-TOF MS 1.7–2.3 hours earlier than the usual time to detection in blood culture systems.
This study provides an approach to earlier identification of BSI pathogens prior to the detection of a positive signal in the blood culture system using MALDI-TOF MS, compared to current methods. It can speed the time for identification of BSI pathogens and may have benefits of earlier therapy choice and on patient outcome.
Blood culture system, Blood stream infection, Mass spectrometry, Matrix-assisted laser desorption ionization–time of flight mass spectrometry, Time to detection