Matrix-assisted laser desorption/ionization time of flight mass spectrometry identification of Vibrio (Listonella) anguillarum isolated from sea bass and sea bream

Shewanella spp. from wastewater treatment plant-affected environment: isolation and characterization

Bacteria from the genus Shewanella are inhabitants of marine and freshwater ecosystems, recognized fish spoilage bacteria, but less known as fish disease agents. Shewanella spp. isolated from fish living in waters close to effluents of a wastewater treatment plant (WWTP) were not previously characterized. We have tested Shewanella isolates from WWTP-affected waters and related fish. Genotypic characterization identified most strains as S. baltica and S. oneidensis. In order to investigate the sensibility and accuracy of their MALDI-TOF MS identification, they were grown on two culture media enriched by various NaCl concentrations, incubated at different temperatures and duration. We analyzed their antimicrobial susceptibility on a panel of antimicrobial drugs and capacity for biofilm production. With a view to demonstrate their capacity to produce fatty acids, we assessed the impact of different culture media on their lipid profile. We performed zebrafish embryotoxicity tests to simulate the environmental infection of the earliest life stages in S. baltica-contaminated waters. The best MALDI-TOF MS identification scores were for strains cultivated on TSA for 24 h at 22 °C and with supplementation of 1.5% NaCl. Less than 17% of isolates demonstrated antimicrobial resistance. Most isolates were weak biofilm producers. Strain-to-strain variation of MIC and MBC was low. The major fatty acids were C15:0, C16:0, C16:1, C17:1, and iC15:0. Exposure of Danio rerio to different S. baltica concentrations induced severe effects on zebrafish development: decreased heartbeat rate, locomotor activity, and melanin pigmentation. S. baltica passed through chorionic pores of zebrafish.

Characterization of Vibrio Populations from Cultured European Seabass and the Surrounding Marine Environment with Emphasis on V. anguillarum

Vibrio species are widely distributed and can be potentially pathogenic to aquatic organisms. In this study, we isolated Vibrio spp. from environmental samples (seawater, sediment, and fish swabs) collected over a three-year period from a fish farm in Mali Ston Bay in the Adriatic Sea, Croatia, and assess their distribution. A total of 48 seawater samples and 12 sediment samples, as well as gill and skin swabs from 110 farmed European seabass, were analysed for the presence of Vibrio. Vibrio strains were identified to the species level by MALDI TOF MS. The analysis revealed that V. alginolyticus was the predominant species in European seabass, followed by V. anguillarum. V. alginolyticus was isolated from the sediments, along with V. gigantis and V. pomeroyi, while V. chagasii, V. cyclitrophicus, V. fortis, V. gigantis, V. harveyi, V. pelagius, and V. pomeroyi were isolated from seawater. V. anguillarum was isolated only twice during two different spring seasons, once from a diseased sea bass and the second time from a healthy sea bass. We analysed these two isolates and found that they differ both genetically and in terms of resistance to antibiotics. Our results confirm the seasonality of vibriosis incidence and the presence of the pathogenic V. anguillarum, which increases the risk of vibriosis.

Sample preparation and culture condition effects on MALDI-TOF MS identification of bacteria: A review

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an excellent tool for bacterial identification. It allows high throughput, sensitive and specific applications in clinical diagnostics and environmental research. Currently, there is no optimal standardized protocol for sample preparation and culture conditions to profile bacteria. The performance of MALDI-TOF MS is affected by several variables, such as sample preparation, culture media and culture conditions, incubation time/growth stage, incubation temperature, high salt content, blood in the culture media, and others. This review thus aims to clarify why a uniformed protocol is not plausible, to assess the effects these factors have on MALDI-TOF MS identification score, and discuss possible optimizations for its methodology, in relation to specific bacterial representatives and strain requirements.

Main bacterial species causing clinical disease in ornamental freshwater fish in Brazil

Bacterial diseases are common in ornamental fish, more frequently associated with ubiquitous bacteria from the aquarium environment. The disease can lead to fish mortality and cause high economic losses if not rapidly controlled. The aim of this study was to identify the main causative bacterial agents of infection in ornamental fish with different clinical signs. A total of 126 freshwater fish, from 12 families and 38 species, with clinical signs were collected in a wholesaler in São Paulo, SP, Brazil. Samples were taken from the eye, skin ulcers, kidneys, and gills, plated on MacConkey, CHROMagar Orientation, and blood agar and incubated under aerobic and anaerobic conditions. Bacterial identification was performed by MALDI-TOF mass spectrometry. From the 126 studied animals, 112 were positive for bacterial isolation. Among the positive animals, 32.1% presented infection caused by a single bacterial species, while in the remaining 67.9%, two to six different bacterial species were identified. A total of 259 bacterial strains were obtained and classified among 46 bacterial species. The species of higher frequency were Aeromonas veronii (26.3%), Aeromonas hydrophilla (16.2%), Shewanella putrefaciens (7.3%), Citrobacter freundii (8.1%), Vibrio albensis (5.8%), and Klebsiella pneumoniae (4.2%). MALDI-TOF MS showed to be a rapid method for diagnosis of bacterial disease outbreaks in ornamental fish establishments.

Rapid Identification of Vibrio Species of the Harveyi Clade Using MALDI-TOF MS Profiling With Main Spectral Profile Database Implemented With an In-House Database: Luvibase

Vibrio bacteria, and particularly members of the Harveyi clade, are the causative agents of vibriosis. This disease is responsible for mass mortality events and important economic losses on aquaculture farms. Improvements in surveillance and diagnosis are needed to successfully manage vibriosis outbreaks. 16S rRNA gene sequencing is generally considered to be the gold standard for bacterial identification but the cost and long processing time make it difficult to apply for routine identification. In contrast, MALDI-TOF MS offers rapid diagnosis and is commonly used in veterinary laboratories today. The major limiting factor for using this technique is the low environmental bacterial diversity in the commonly available databases. Here, we demonstrate that the sole use of the commercially available Bruker BioTyper database is not fully adequate for identifying Vibrio bacteria isolated from aquaculture farms. We therefore developed a new in-house database named Luvibase, composed of 23 reference MALDI-TOF mass spectra profiles obtained from Vibrio collection strains, mostly belonging to the Harveyi clade. The comparison of the accuracy of MALDI-TOF MS profiling and 16S rRNA gene sequencing revealed a lack of resolution for 16S rRNA gene sequencing. In contrast, MALDI-TOF MS profiling proved to be a more reliable tool for resolving species-level variations within the Harveyi clade. Finally, combining the Luvibase with the Bruker ver.9.0.0.0 database, led to successful identification of 47 Vibrio isolates obtained from moribund abalone, seabass and oysters. Thus, the use of Luvibase allow for increased confidence in identifying Vibrio species belonging to the Harveyi clade.

Proteomic Strategies to Evaluate the Impact of Farming Conditions on Food Quality and Safety in Aquaculture Products

This review presents the primary applications of various proteomic strategies to evaluate the impact of farming conditions on food quality and safety in aquaculture products. Aquaculture is a quickly growing sector that represents 47% of total fish production. Food quality, dietary management, fish welfare, the stress response, food safety, and antibiotic resistance, which are covered by this review, are among the primary topics in which proteomic techniques and strategies are being successfully applied. The review concludes by outlining future directions and potential perspectives.