Identification of bacterial pathogens in cultured fish with a custom peptide database constructed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)
The majority of infectious diseases of cultured fish is caused by bacteria. Rapid identification of bacterial pathogens is necessary for immediate management. The present study developed a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for rapid identification of fish bacterial pathogens. Streptococcus agalactiae, Streptococcus iniae, Aeromonas hydrophila, Aeromonas veronii, and Edwardsiella tarda obtained from diseased fish were used as
... sed as representative bacterial pathogens in this study. Bacterial peptides were extracted to create a Main Spectra Profile (MSP), and the MSPs of each bacterial species was added into the MALDI Biotyper database. Fifteen additional isolates of each bacterial species were tested to validate the utilized technique. Results: The MSPs of all field isolates were clearly distinguishable, and the MSPs of the same species were clustered together. However, the species identification when matched with the public MALDI Biotyper library (Bruker MALDI Biotyper) showed unreliable results. Accurate identification was only obtained when using the custom-made database, giving a 100% matching result with the reference method. Conclusion: This study demonstrates an alternative technique for effective identification of fish bacterial pathogens. Further applications require a broad, wellestablished database to accommodate prudent identification of many fish bacterial pathogens by MALDI-TOF MS. Background Bacterial pathogens are a major etiology of infectious diseases of cultured fish . Among those bacteria, Streptococcus spp., Aeromonas spp., and Edwardsiella spp., are commonly found in several important aquaculture species, such as the Asian catfish Clarias batrachus , barramundi Lates calcarifer , and Nile tilapia Oreochromis niloticus . In many cases of bacterial infection, clinical signs and lesions are not obviously apparent and may mislead the diagnosis. Therefore, identification of disease-causing bacterial species is necessary in order to carry out proper disease management. Conventional microbiology techniques, including morphological, physiological and biochemical tests, and molecular techniques based on 16S rDNA sequencing, are the gold standard for bacterial species identification . However, these techniques require a substantial amount of time and expensive Availability of data and materials The datasets used and analyzed during the study are available from the corresponding author upon request. Ethics approval and consent to participate Not applicable.