Recovery of Bacillus mycoides,B. pseudomycoides and Aeromonas hydrophila from common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) with gill disease

During a 3‐month period from June to the end of August 2016, ~5% mortalities were observed in a farm with rainbow trout (Oncorhynchus mykiss Walbaum) and one farm of common carp (Cyprinus carpio L.) in Bulgaria. The disease was manifested by gill ulcers/rot, asphyxiation and bloody ascites. Aeromonas hydrophila was isolated from the internal organs of all the diseased fish. Bacillus mycoides or B. pseudomycoides were recovered from the gill lesions on diseased carp and rainbow trout, respectively, with identification achieved by conventional phenotyping and by sequencing of the 16S rRNA gene. In vivo experiments confirmed that all three organisms were pathogenic to rainbow trout.     

It’s a maze: The pore structure of bread crumbs

Bread has a foam-like structure, but to date there is little information about the morphology of void structure in breads in three dimensions. In this paper, permeability testing and analysis of computer aided micro-tomography data were used to investigate the structure of breads as a function of connectivity of voids in a range of breads. The findings were related to bread properties obtained via material testing. Results indicated that a single, massively interconnected, open cell was responsible for approximately 99% of bread’s total porosity. Closed pores are also present with the number and average volume of closed pores significantly affecting strengths of bread crumbs. Bread behaved similarly to foams described by Gibson and Ashby (1988). The role of open and closed pores in affecting bread toughness and texture requires further investigation via structural–mechanical models.     

Probiotics,immunostimulants, plant products and oral vaccines,and their role as feed supplements in the control of bacterial fish diseases

There is a rapidly increasing literature pointing to the success of probiotics, immunostimulants, plant products and oral vaccines in immunomodulation, namely stimulation of the innate, cellular and/or humoral immune response, and the control of bacterial fish diseases. Probiotics are regarded as live micro‐organisms administered orally and leading to health benefits. However, in contrast with the use in terrestrial animals, a diverse range of micro‐organisms have been evaluated in aquaculture with the mode of action often reflecting immunomodulation. Moreover, the need for living cells has been questioned. Also, key subcellular components, including lipopolysaccharides, have been attributed to the beneficial effect in fish. Here, there is a link with immunostimulants, which may also be administered orally. Furthermore, numerous plant products have been reported to have health benefits, namely protection against disease for which stimulation of some immune parameters has been reported. Oral vaccines confer protection against some diseases, although the mode of action is usually linked to humoral rather than the innate and cellular immune responses. This review explores the relationship between probiotics, immunostimulants, plant products and oral vaccines.     

Identification and pathogenicity to rainbow trout, Oncorhynchus mykiss (Walbaum), of some aeromonads

Twelve strains of fish pathogenic aeromonads were identified by 16S rRNA sequencing as Aeromonas bestiarum , A. hydrophila , A. hydrophila subsp. dhakensis , A. salmonicida subsp. salmonicida , A. sobria biovar sobria and A. veronii biovar sobria. Following intramuscular injection, A. hydrophila subsp. dhakensis caused dark liquefying, raised furuncle-like lesions in rainbow trout within 48 h. Extracellular products of all cultures contained gelatinase and lecithinase, and most revealed lipase. Congo red absorption and siderophore production was recorded, but not so the suicide phenomenon or slime production. Sodium dodecyl sulphate polyacrylamide gel electrophoresis profile of the outer membrane proteins (OMP) revealed 10–25 bands, of which major bands were seen in the region of 32.5–47.5 and 62–83 kDa. Marked heterogenicity of the OMP and whole cell protein (WCP) profiles within and among the species was observed. Polypeptides of 83–173 kDa were detected in the WCP profile of the cultures, but they were not expressed in OMP fractions.     

Use of probiotics to control furunculosis in rainbow trout, Oncorhynchus mykiss (Walbaum)

Aerobic heterotrophic bacteria were isolated from the intestinal contents of Atlantic salmon, Salmo salar , rainbow trout, Oncorhynchus mykiss , and turbot, Scophthalmus maximus , on tryptone soya agar and De Man Rogosa and Sharpe agar, of which 11 of 177 (6% of the total) of the isolates were antagonistic to Aeromonas salmonicida . Four of these cultures, which were identified tentatively as A. hydrophila , Vibrio fluvialis , Carnobacterium sp. and an unidentified Gram-positive coccus, were beneficial to fish when fed singly or as an equi-mixture. Feed supplemented with the putative probiotics indicated survival of the organisms in the gastrointestinal tract for 7 days. Feeding with the probiotics for 7 and 14 days led to better survival following challenge with A. salmonicida . There was no indication of serum or mucus antibodies to A. salmonicida , but there was an increased number of erythrocytes, macrophages, lymphocytes and leucocytes, and enhanced lysozyme activity in the fish.     

Subcellular components of Vibrio harveyi and probiotics induce immune responses in rainbow trout, Oncorhynchus mykiss (Walbaum), against V. harveyi

Bacterial subcellular components and probiotics were successful for the stimulation of immunity and the prevention of Vibrio harveyi infections in rainbow trout, Oncorhynchus mykiss (Walbaum). Rainbow trout were immunized with whole inactivated cells of V. harveyi to obtain polyclonal antibodies against specific antigens. Western blotting showed a unique reactive band (∼93 kDa) between serum and bacterial proteins from outer membrane proteins (OMP) and extracellular products (ECP). Probiotics were selected according to their capability to inhibit V. harveyi . Two of these bacteria, i.e. A3-47 and A3-51, showed cross-reactivity with V. harveyi antiserum. Their OMPs and ECPs were reactive with V. harveyi antiserum in bands of ∼93 kDa for A3-51 and higher for A3-47. In vivo tests determined that fish fed with A3-51 produced cross-reactive antibodies against V. harveyi and also, the survival of these fish infected with V. harveyi was high, being similar to the level achieved with vaccinated fish. Thus, the probiotics, when administered as live preparations, were capable of producing cross-reactive antibody against specific bacterial pathogens.