Strain-Level Characterization of Legionella Environmental Isolates via MALDI-TOF-MS

David Otto Schwake; Todd Sandrin; Lin Zhang; Morteza Abbaszadegan

doi:10.3390/microorganisms11010008

Strain-Level Characterization of Legionella Environmental Isolates via MALDI-TOF-MS

Microorganisms. 2022 Dec 20;11(1):8. doi: 10.3390/microorganisms11010008.

Authors

David Otto Schwake¹, Todd Sandrin², Lin Zhang³, Morteza Abbaszadegan⁴

Affiliations

¹ Department of Natural Sciences, Middle Georgia State University, 100 University Pkwy, Macon, GA 31206, USA.
² School of Mathematical and Natural Sciences, New College of Interdisciplinary Arts & Sciences, Arizona State University at the West Campus, 4701 W. Thunderbird Road, Glendale, AZ 85306, USA.
³ China Innovation Center, Shimadzu (China) Co., Beijing Branch, Beijing 100020, China.
⁴ School of Sustainable Engineering and the Built Environment, Arizona State University at the Tempe Campus, 1151 S. Forest Ave, Tempe, AZ 85281, USA.

Abstract

As a waterborne pathogen of increasing concern, techniques for cost-effective and rapid characterization of Legionella are vital. This study examines the development of a Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF-MS) analysis methodology for this microbe. First, optimal sample preparation methods for the analysis of environmental Legionella isolates via MALDI-TOF-MS were determined. These methods were then implemented to perform strain-level characterization of environmental Legionella isolates from central Arizona. Results demonstrate that a MALDI-TOF-MS method involving BCYE agar-based culturing and protein extraction-based sample preparation yield high-quality mass spectra. Twenty-eight environmental Legionella isolates originating from two separate drinking water distribution systems were analyzed. Multiple species were detected, and strain-level characterization was achieved, with 12 unique strains distinguished. In addition, isolates of L. pneumophila, the most common species observed in the study, were correctly assigned to specific sampling sites. These results demonstrate the potential for this technique to be applied for sub-species characterization of Legionella with significant benefits over established methodologies.

Keywords: MALDI; cluster analysis; pneumophila; typing; water distribution systems.

Grants and funding

This research was supported in part by the National Science Foundation (NSF) Water and Environmental Technology (WET) Center at Arizona State University (award number 1361815) and the New College of Interdisciplinary Arts and Sciences at Arizona State University.