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Utilization of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) to Identify environmental Strains of Mycobacterium Complex
Citation:
DONOHUE, M. J., J. H. Mistry, AND S. L. PFALLER. Utilization of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) to Identify environmental Strains of Mycobacterium Complex. Presented at American Society for Microbiology Annual Meeting, Philadelphia, PA, May 17 - 21, 2009.
Impact/Purpose:
To identify a MAC isolate to the species level by MALDI/MS. Criteria for Success: Each species within the MAC must have a unique m/z signature that can be used for identification. Definition: An m/z signature is a collection of proteins that are detected by the MALDI-MS that have a specific mass (Da) to charge (ionization state) ratio.
Description:
Species within the Mycobacterium avium Complex (MAC) group are found to be both prevalent and persistent in drinking water distribution systems. The MAC is composed of two predominant species: M. avium and M. intracellulare. These species have the ability to survive drinking water disinfection treatments and to thrive in distribution systems via biofilms. For these reasons, the US Environmental Protection Agency (EPA) has listed MAC on the Contaminant Candidate List (CCL) as a potential contaminant that may require regulation if it is proven to have a significant health burden to the public. A major challenge associated with environmental MAC isolates is the ability to rapidly identify the isolate to the species level. The tools currently available for identification/speciation can be time-consuming, as well as give ambiguous results due to their inability to clearly differentiate species. The purpose of this study was to evaluate Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) as a means to rapidly speciate MAC environmental isolates. The research presented will demonstrate the use of MALDI-MS to speciate environmental isolates based on their m/z signature. Initially, a database of m/z signatures was constructed using MAC reference and type strains. Next, m/z signatures from environmental isolates were compared to the database of known m/z signatures. Additionally, DNA sequence analyses of genes coded for the heat shock protein 65 (hsp65), RNA polymerase subunit B (rpoB), and 16S rRNA were used to validate the MALDI-MS determination. MALDI-MS analysis is ideal for the identification/speciation of environmental isolates. This is primarily due to the minimal sample preparation involved (i.e., the ability to go from culture plate directly to analysis), as well as the short analysis time (<2 min) before a determination can be made. These traits make MALDI-MS a powerful tool suited for environmental monitoring and identification of microbial hazards in drinking water.