Molecular phylogenetic and matrix-assisted laser desorption ionization time-of-flight mass spectrometry identification of isolates from horses identified as Enterobacter cloacae by biochemical identification

Eri Uchida-Fujii; Hidekazu Niwa; Yuta Kinoshita; Yoshinari Katayama; Toshio Nukada

doi:10.1294/jes.31.49

Molecular phylogenetic and matrix-assisted laser desorption ionization time-of-flight mass spectrometry identification of isolates from horses identified as Enterobacter cloacae by biochemical identification

J Equine Sci. 2020 Oct;31(3):49-55. doi: 10.1294/jes.31.49. Epub 2020 Oct 5.

Authors

Eri Uchida-Fujii¹, Hidekazu Niwa¹, Yuta Kinoshita¹, Yoshinari Katayama¹, Toshio Nukada¹

Affiliation

¹ Microbiology Division, Equine Research Institute, Japan Racing Association, Tochigi 329-0412, Japan.

Abstract

Enterobacter cloacae is an opportunistic pathogen of horses. Thirty isolates obtained from horses and their environments and identified as Enterobacter cloacae by biochemical methods were reidentified by taxonomic identification based on multilocus sequence analysis (MLSA) and by a commercial identification system based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). MLSA identified the 30 equine isolates as E. ludwigii (9/30), E. asburiae (1/30), or E. cloacae (1/30); 19 isolates were not identified. The MALDI-TOF MS system could not clearly distinguish isolates to the species level, and the limited numbers of reference spectra for Enterobacter species might have contributed to the poor identification.

Keywords: Enterobacter species; horse; matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS); multilocus sequence analysis (MLSA).