Mass spectrometry-based microbiological testing for blood stream infection

Area of Science:

• Clinical Microbiology
• Analytical Chemistry
• Infectious Diseases

Background:

• Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a key technology for identifying microorganisms in laboratory medicine, particularly in bloodstream infections.
• Direct identification from positive blood culture bottles is crucial for timely diagnosis and treatment.
• Existing commercial kits for sample preparation have limitations, including cost and variable performance, especially for Gram-positive bacteria.

Purpose of the Study:

• To describe and evaluate MALDI-TOF MS-based methods for direct bacterial identification from positive blood cultures.
• To compare the performance of a developed home-brew protocol, Centrifugation and Membrane Filtration Technique (CMFT), against a commercial kit (Sepsityper®).
• To discuss the evolving role of Liquid Chromatography coupled with tandem Mass Spectrometry (LC-MS/MS) in antimicrobial susceptibility testing.

Main Methods:

• Evaluation of direct identification protocols for MALDI-TOF MS from positive blood culture bottles.
• Development and prospective evaluation of a home-brew Centrifugation and Membrane Filtration Technique (CMFT) protocol.
• Comparison of CMFT performance against the commercial Sepsityper® kit using 170 monomicrobial positive blood cultures.

Main Results:

• The CMFT protocol demonstrated significantly better performance than the Sepsityper® kit, particularly for Gram-positive bacterial isolates.
• MALDI-TOF MS-based identification from polymicrobial blood specimens remains challenging.
• Current MALDI-TOF MS applications are limited in assessing antibiotic susceptibility and resistance.

Conclusions:

• MALDI-TOF MS is an indispensable tool for rapid bacterial identification in bloodstream infections.
• The development of improved sample preparation methods enhances diagnostic accuracy.
• Liquid Chromatography coupled with tandem Mass Spectrometry (LC-MS/MS) is expected to play an increasing role in antimicrobial susceptibility and resistance assessment.