Matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid identification of Brachyspira species isolated from swine, including the newly described "Brachyspira hampsonii"

The Brachyspira species traditionally associated with swine dysentery and other diarrheal diseases in pigs are Brachyspira hyodysenteriae, Brachyspira pilosicoli, and, to a lesser extent, Brachyspira murdochii. "Brachyspira hampsonii" is a recently proposed novel species that causes clinical disease similar to that caused by B. hyodysenteriae. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems are increasingly available in veterinary diagnostic laboratories, are less expensive, and are faster than traditional microbiological and molecular methods for identification. Thirty-three isolates associated with Brachyspira species of importance to swine were added to an existing MALDI-TOF MS database library. In total, species included in the library were: B. hyodysenteriae, "B. hampsonii" clades I and II, Brachyspira innocens, Brachyspira intermedia, B. murdochii, and B. pilosicoli. A comparison between MALDI-TOF MS and nox sequencing was completed on 176 field isolates. Of the 176 field isolates, 174 (98.9%) matched species identification by both methods. Thirty field isolates were identified by both methods as "B. hampsonii". Twenty-seven of the 30 (90%) "B. hampsonii" field isolates matched clade designation in both assays. The nox sequencing identified 26 as "B. hampsonii" clade I and 4 as clade II. Comparatively, MALDI-TOF MS identified 25 of the 30 as "B. hampsonii" clade I and 5 as clade II. The current study indicates MALDI-TOF MS is a reliable tool for the identification of swine Brachyspira species; however, final clade designation for "B. hampsonii" may still require molecular techniques.