Influence of probiotic strain Bifidobacterium longum on the intestinal microbiome of carp

The gastrointestinal tract of animals represents the front line of the defense system against various pathogens that enter the body with food and can colonize cells and tissues of the host. The purpose of the study was to evaluate the influence of probiotic strain Bifidobacterium longum (“Soya-bifidum”) on the intestinal microbiome of carp. On the basis of the department of biotechnology of animal raw materials and aquaculture of the Orenburg State University in the conditions of the aquarium stand an experiment on the yearlings of carp for 56 days was conducted. Three groups of fish were formed by the paired-analog method: a control group and two experimental groups. The control group was on the basic diet, and the experimental groups were additionally given probiotic strain Bifidobacterium longum (I experimental group) in an amount of 0.7 ml/kg of feed and the antibiotic ciprofloxacin hydrochloride (II experimental group) in an amount of 100 mg/kg of feed. Analysis of fish gut microbiome showed that the predominant bacterial types in experimental carp were Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes and Fusobacteriota. It was found that the addition of Bifidobacterium longum to the diet of carp was associated with an increase in the intestinal phylum Actinobacteria and a decrease in conditionally pathogenic phylum Firmicutes. Also in the intestines of fish was revealed the genus Bifidobacterium which are microorganisms that have a positive effect on the composition and number of microflora in the intestines through the production of antibiotic substances that prevent the growth of pathogens, in particular bacteria of the genus Aeromonas. The addition of antibiotics to the fish diet leads to an increase in the number of Proteobacteria and its constituent class Gammaproteobacteria with an increase in the number of bacteria genera Aeromonas and Pseudomonas, which indicates a violation of the normal gut microflora and increase the number of non-sanitary microorganisms and can lead to epizootics.