Species-specific identification and differentiation of Arcobacter, Helicobacter and Campylobacter by full-spectral matrix-associated laser desorption/ionization time of flight mass spectrometry analysis

Abstract

Rapid and reliable identification of Arcobacter and Helicobacter species, and their distinction from phenotypically similar Campylobacter species, has become increasingly important, since many of them are now recognized as human and/or animal pathogens. Matrix-associated laser desorption/ionization-time of flight (MALDI-TOF) MS has been shown to be a rapid and sensitive method for characterization of micro-organisms. In this study, we therefore established a reference database of selected Arcobacter, Helicobacter and Campylobacter species for MALDI-TOF MS identification. Besides the species with significance as food-borne pathogens - Arcobacter butzleri, Helicobacter pullorum, Campylobacter jejuni and Campylobacter coli - several other members of these genera were included in the reference library to determine the species specificity of the designed MALDI Biotyper reference database library. Strains that made up the reference database library were grown on Columbia agar, and yielded reproducible and unique mass spectra profiles, which were compared with the Bruker Biotyper database, version 2. The database was used to identify 144 clinical isolates using whole spectral profiles. Furthermore, reproducibility of MALDI-TOF MS results was evaluated with respect to age and/or storage of bacteria and different growth media. It was found that correct identification could be obtained even if the bacteria were stored at room temperature or at 4 degrees C up to 9 days before being tested. In addition, bacteria were correctly identified when grown on Campylosel agar; however, they were not when grown on modified charcoal cefoperazone deoxycholate agar. These results indicate that MALDI-TOF MS fingerprinting is a fast and reliable method for the identification of Arcobacter and Helicobacter species, and their distinction from phenotypically similar Campylobacter species, with applications in clinical diagnostics.