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Volume 48, Number 4, August 2015

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:

Jiunn-Jong Wu
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. 



 

Methods:

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. 



 

Results:

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.
 



 

Conclusion:

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. 



 

Key words:

Blood culture system, Blood stream infection, Mass spectrometry, Matrix-assisted laser desorption ionization–time of flight mass spectrometry, Time to detection