Abstract
Shewanella species are widely distributed in the aquatic environment and aquatic organisms. They are opportunistic human pathogens with increasing clinical infections reported in recent years. However, there is a lack of a rapid and accurate method to identify Shewanella species. We evaluated here matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for rapid identification of Shewanella. A peptide mass reference spectra (PMRS) database was constructed for the type strains of 36 Shewanella species. The main spectrum projection (MSP) cluster dendrogram showed that the type strains of Shewanella species can be effectively distinguished according to the different MS fingerprinting. The PMRS database was validated using 125 Shewanella test strains isolated from various sources and periods; 92.8% (n = 116) of the strains were correctly identified at the species level, compared with the results of multilocus sequence analysis (MLSA), which was previously shown to be a method for identifying Shewanella at the species level. The misidentified strains (n = 9) by MALDI-TOF MS involved five species of two groups, i.e., Shewanella algae–Shewanella chilikensis–Shewanella indica and Shewanella seohaensis–Shewanella xiamenensis. We then identified and defined species-specific biomarker peaks of the 36 species using the type strains and validated these selected biomarkers using 125 test strains. Our study demonstrated that MALDI-TOF MS was a reliable and powerful tool for the rapid identification of Shewanella strains at the species level.
Highlights
The genus Shewanella comprises a group of oxidase, catalase, and ornithine decarboxylase-positive and H2S-producing, facultative anaerobic bacteria with a wide distribution in the environment
Since multilocus sequence analysis (MLSA) has been confirmed to be accurate for identifying Shewanella at the species level (Fang et al, 2019), all 125 test strains were analyzed by MLSA, and the results were used to evaluate the effectiveness of MALDI-TOF MS for species identification
Nine strains were misidentified by MALDI-TOF MS, involving five species of two groups, i.e., S. algae–S. chilikensis–S. indica and S. seohaensis–S. xiamenensis
Summary
The genus Shewanella comprises a group of oxidase-, catalase-, and ornithine decarboxylase-positive and H2S-producing, facultative anaerobic bacteria with a wide distribution in the environment. It plays an important ecological role in many fields such as materials engineering, environmental engineering (Zou et al, 2018), and marine biology (Gorby et al, 2006; Fredrickson et al, 2008; Kouzuma et al, 2015; Daeffler et al, 2017). Some studies have shown that SSTI is the most common clinical features of Shewanella infection, including cellulitis, abscess, or necrotizing fasciitis (Yousfi et al, 2017). Shewanella has been isolated from more and more clinical specimens (Janda and Abbott, 2014)
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