Fish bioenergetics: (Fish and Fisheries 13. Series ed. T.J. Pitcher) Malcolm Jobling Chapman and Hall, London, 1994 ISBN 0-412-58090-X, 24.99 Hard cover, acid-free paper, pp. xiv + 309, 31 tables, 61 figures Author, species and subject indexes

The qualitative and quantitative composition of biofilms on microplastic surfaces is widely unknown. A previous study (Zettler et al., 2013; EST) reports the presence of potentially pathogenic bacteria (Vibrio spp.) on floating microplastic particles. Hence microplastics could function as vectors for the dispersal of microorganisms to new habitats. Several Vibrio species are serious human pathogens. Contact with contaminated water and consumption of raw seafood are the main infection factors for Vibrio associated diseases. On research cruises to the North- and Baltic Sea, microplastic particles were collected and subjected to APW (alkaline peptone water) enrichment. Growth on selective CHROMagar™ Vibrio and further identification of isolates by MALDI-TOF (matrix assisted laser desorption/ionization time-of-flight) clearly indicate the presence of potentially pathogenic Vibrio spp. on microplastics. Our results highlight the urgent need for detailed microbiological analyses of floating microplastic particles in the future.

Dangerous hitchhikers? evidence for potentially pathogenic vibrio spp. on microplastic particles

Flavobacterium columnare (F. columnare) is the causative agent of columnaris disease. This bacterium affects both cultured and wild freshwater fish including many susceptible commercially important fish species. F. columnare infections may result in skin lesions, fin erosion and gill necrosis, with a high degree of mortality, leading to severe economic losses. Especially in the last decade, various research groups have performed studies aimed at elucidating the pathogenesis of columnaris disease, leading to significant progress in defining the complex interactions between the organism and its host. Despite these efforts, the pathogenesis of columnaris disease hitherto largely remains unclear, compromising the further development of efficient curative and preventive measures to combat this disease. Besides elaborating on the agent and the disease it causes, this review aims to summarize these pathogenesis data emphasizing the areas meriting further investigation.

https://biblio.ugent.be/publication/4356262/file/4356809.pdf

Columnaris disease in fish: a review with emphasis on bacterium-host interactions

Use of probiotics in aquaculture of China-a review of the past decade.

Fish gut microbiome confers various effects to the host fish; this includes overall size, metabolism, feeding behaviour and immune response in the fish. The emergence of antimicrobial-resistant (AMR) bacteria and hard to cure fish diseases warrant the possible utilization of gut microbes that exhibits a positive effect on the fish and thus lead to the usage of these microbes as probiotics. The widespread and systematic use of antibiotics has led to severe biological and ecological problems, especially the development of antibiotic resistance that affects the gut microbiota of aquatic organisms. Probiotics are proposed as an effective and environmentally friendly alternative to antibiotics, known as beneficial microbes. At the same time, prebiotics are considered beneficial to the host's health and growth by decreasing the prevalence of intestinal pathogens and/or changing the development of bacterial metabolites related to health. Uprise of sequencing technology and the development of intricate bioinformatics tools has provided a way to study these gut microbes through metagenomic analysis. From various metagenomic studies, ample of information was obtained; such information includes the effect of the gut microbiome on the physiology of fish, gut microbe composition of different fish, factors affecting the gut microbial composition of the fish and the immunological effect of gut microbes in fish; such this information related to the fish gut microbiome, their function and their importance in aquaculture is discussed in this review.

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Gut microbiota metagenomics in aquaculture: factors influencing gut microbiome and its physiological role in fish

Flavobacterium columnare is the causative agent of columnaris disease in diverse fish species worldwide. Although columnaris is an important disease, the antimicrobial susceptibility pattern of F. columnare is not well studied. Thus, the purpose of this study was to test the in vitro antimicrobial susceptibility of 97 F. columnare isolates collected worldwide between 1987 and 2011 from 17 fish species. The broth microdilution technique was utilized for reliable testing of these fastidious organisms. None of the isolates displayed acquired resistance to florfenicol, gentamicin, ormetoprim-sulfadimethoxine and trimethoprim-sulfamethoxazole. Acquired resistance to chloramphenicol was detected in 1%, to nitrofuran in 5%, to oxytetracycline in 11% and to enrofloxacin, flumequine and oxolinic acid in 10%, 16% and 16% of the isolates, respectively, as reflected by a bimodal or trimodal distribution of their minimum inhibitory concentrations (MICs). One isolate showed acquired resistance towards several antimicrobial agents including erythromycin. Another isolate revealed acquired resistance towards amongst others ampicillin. The isolates displaying acquired resistance originated from ornamental fish species or Vietnamese catfish, except for two isolates coming from wild channel catfish in which acquired resistance was encountered towards oxytetracycline only. Fifty per cent of the resistant isolates from ornamental fish were shown to have acquired resistance against three classes of antimicrobial agents, assigning these isolates as multiple resistant. These data might indicate less prudent use of antimicrobials especially in ornamental fish species.

Antimicrobial susceptibility pattern of Flavobacterium columnare isolates collected worldwide from 17 fish species.

Challenge models generating gill lesions typical for columnaris disease were developed for the fry of both Common Carp Cyprinus carpio and Rainbow Trout Oncorhynchus mykiss by means of an immersion challenge and Flavobacterium columnare field isolates were characterized regarding virulence. Carp inoculated with highly virulent isolates revealed diffuse, whitish discoloration of the gills affecting all arches, while in trout mostly unilateral focal lesions, which were restricted to the first two gill arches, occurred. Light microscopic examination of the gills of carp exposed to highly virulent isolates revealed a diffuse loss of branchial structures and desquamation and necrosis of gill epithelium with fusion of filaments and lamellae. In severe cases, large parts of the filaments were replaced with necrotic debris entangled with massive clusters of F. columnare bacterial cells enwrapped in an eosinophilic matrix. In trout, histopathologic lesions were similar but less extensive and much more foca...

Gill Infection Model for Columnaris Disease in Common Carp and Rainbow Trout

The interactions of Flavobacterium columnare isolates of different virulence with the gills of carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum) were investigated. Both fish species were exposed to different high (HV) or low virulence (LV) isolates and sacrificed at seven predetermined times post-challenge. Histopathological and ultrastructural examination of carp and rainbow trout inoculated with the HV-isolate disclosed bacterial invasion and concomitant destruction of the gill tissue, gradually spreading from the filament tips towards the base, with outer membrane vesicles surrounding most bacterial cells. In carp, 5-10% of the fish inoculated with the LV-isolate became moribund and their gill tissue displayed the same features as described for the HV-isolate, albeit to a lesser degree. The bacterial numbers retrieved from the gill tissue were significantly higher for HV- compared to LV-isolate challenged carp and rainbow trout. TUNEL-stained and caspase-3-immunostained gill sections demonstrated significantly higher apoptotic cell counts in carp and rainbow trout challenged with the HV-isolate compared to control animals. Periodic acid-Schiff/alcian blue staining demonstrated a significantly higher total gill goblet cell count for HV- and LV-isolate challenged compared to control carp. Moreover, bacterial clusters were embedded in a neutral matrix while being encased by acid mucins, resembling biofilm formation. Eosinophilic granular cell counts were significantly higher in the HV-isolate compared to LV-isolate inoculated and control carp. The present data indicate a high colonization capacity, and the destructive and apoptotic-promoting features of the HV-isolate, and point towards important dynamic host mucin–F. columnare interactions warranting further research.

https://biblio.ugent.be/publication/5798866/file/5905120.pdf

Annelies Declercq

Papers

Columnaris disease in fish: a review with emphasis on bacterium-host interactions

Antimicrobial susceptibility pattern of Flavobacterium columnare isolates collected worldwide from 17 fish species.

Gill Infection Model for Columnaris Disease in Common Carp and Rainbow Trout

Interactions of highly and low virulent Flavobacterium columnare isolates with gill tissue in carp and rainbow trout

Microplastic detection and identification by Nile red staining: Towards a semi-automated, cost- and time-effective technique.