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Probiotics and Aquaculture


Probiotics and Aquaculture Professor B. Austin Fish diseases Description of new pathogens (e.g. Yersinia ruckeri biotype 1; organism related to ultramicrobacterium ... – PowerPoint PPT presentation

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Title: Probiotics and Aquaculture

Probiotics and Aquaculture
  • Professor B. Austin

Fish diseases
Biological information
  • Description of new pathogens (e.g. Yersinia
    ruckeri biotype 1 organism related to
  • Improved taxonomy (vibrios aeromonads)
  • Ecology (role of Aeromonas in the aquatic
  • Pathogenicity (role of bacteriophage in the
    pathogenicity of Vibrio harveyi)

Disease diagnosis
  • Serology (ELISAs developed for field use)
  • Molecular methods (sequencing)

Disease control
  • Improved husbandry/management
  • Movement restrictions
  • Genetic improvement of stock
  • Antimicrobial compounds (possibly will be banned
    in future)
  • Non-specific immunostimulants (e.g. ß, 1-3
    glucan LPS)
  • Dietary supplements (vitamins, etc)
  • Water treatments
  • Vaccines (greater range of antigens needed
    improved adjuvants and oralisers
  • Probiotics (biological control?)

Probiotics in aquaculture
  • See Health and Nutritional Properties of
    Probiotics in Food including Powder Milk with
    Live Lactic Acid Bacteria - FAO.
  • The term probiotic is a relatively new word
    meaning for life and is currently used to name
    bacteria associated with beneficial effects for
    humans and animals.
  • The original observation of the positive role
    played by some selected bacteria is attributed to
    Eli Metchnikoff, the Russian born Nobel Prize
    recipient working at the Institut Pasteur at the
    beginning of the last century, who suggested that
    "The dependence of the intestinal microbes on the
    food makes it possible to adopt measures to
    modify the flora in our bodies and to replace the
    harmful microbes by useful microbes"
    (Metchnikoff, 1907).

Probiotics in aquaculture
  • The word "probiotic" was not coined until 1960,
    to name substances produced by micro-organisms
    which promoted the growth of other
  • In order to be termed a probiotic, the
    micro-organism must be able to confer defined
    health benefits on the host, in the actual
    product vehicle that will be made available to

  • Fuller (1987) considered that a probiotic is a
    cultured product or live microbial feed
    supplement, which beneficially affects the host
    by improving its intestinal (microbial) balance.
    The probiotic should provide actual benefit to
    the host, be able to survive in the digestive
    tract, be capable of commercialisation, i.e.
    grown on an industrial scale, and should be
    stable and viable for prolonged storage
    conditions, and in the field.
  • FAO/WHO a live micro-organism, which when
    consumed in adequate amounts, confers a health
    effect on the host
  • Other workers have broadened the definition, for
    example removing any association with feed (use
    in water?), or the need for live cells.

It is clear that
  • Probiotics must not be harmful to the host
  • They need to be effective over a range of
    temperature extremes and variations in salinity

  • There could be confusion between a probiotic
    applied by the oral route, injection or
    immersion, and a vaccine?
  • Confusion could have legal implications, for
    example, are they feed additives or oral vaccines?

Is the effect genuine or could the probiotic
really be a placebo?
Probiotics evaluated in aquaculture
Gram-positive bacteria
  • Bacillus spp.
  • Bacillus toyoi
  • Entrecoccus faecium
  • Micrococcus luteus
  • Weissella hellenica

lactic-acid producing bacteria (Carnobacterium
divergens, Carnobacterium inhibens, Lactobacillus
plantarum, Lactobacillus helveticus,
Lactobacillus rhamnosus, Lactococcus lactis)
Probiotics evaluated in aquaculture
Gram-negative bacteria
  • Aeromonas hydrophila
  • Aeromonas media
  • Alteromonas
  • Photorhodobacterium
  • Pseudomonas fluorescens
  • Pseudomonas spp.
  • Roseobacter
  • Vibrio alginolyticus
  • Vibrio fluvialis
  • Vibrio proteolyticus

Probiotics evaluated in aquaculture
  • Debaryomyces hansenii
  • Phaffia rhodozyma
  • Saccharomyces cerevisiae
  • S. exiguous
  • Tetraselmis suecica

  • Lipopolysaccharides (LPS)
  • Vibrio vaccines
  • Clostridium butyricum spores
  • Glucan from yeast cell walls

(increase phagocytosis, antibody production,
increase the chemiluminescent response, and
superoxide anion production).
Benefits of probiotics
  • Reduction in mortalities
  • Lead to reduction in the levels of antimicrobial
  • Lead to improved appetite and/or growth

Source of probiotics
  • Seawater
  • Beach sand
  • Fish guts
  • Commercial preparations

Mode of action of probiotics
  • Improved nutrition - enzymes (biotin, B12)
  • Stimulation of humoral and/or cellular immune
    response (phagocytic and lysozyme activities)
  • Alteration of microbial metabolism by the
    increase or decrease of relevant (digestive)
    enzyme levels
  • Competitive exclusion by which the probiotic
    antagonises the potential pathogen by colonising
    the gut, producing inhibitory compounds or
    competing for nutrients, space ( adhesion sites
    in the digestive tract) or oxygen

Vibrio alginolyticus
  • Used extensively in Ecuador
  • Claims to have reduced mortalities and the need
    for antibiotics by gt90
  • Weakly inhibitory to fish pathogens
  • Protected salmonids against subsequent challenge
    by Aeromonas salmonicida and Vibrio anguillarum

Carnobacterium inhibens K
  • Recovered from the digestive tract of salmonids
    and turbot
  • Weakly inhibitory to fish pathogens
  • Protected salmonids against subsequent challenge
    by Aeromonas salmonicida and Vibrio anguillarum

Aeromonas salmonicida, A. sobria, Brochothrix
thermosphacta, Micrococcus
  • Recovered from the digestive tract of salmonids
    and turbot
  • Weakly inhibitory to Aeromonas salmonicida
  • Harmless following injection of salmonids
  • Stimulated appetite (aggressively)
  • 14-day feeding regime was effective at resisting
    challenge by A. salmonicida

Aeromonas salmonicida, A. sobria, Brochothrix
thermosphacta, Micrococcus
  • Dead cells were as effective as live preparations
  • Field evidence - less none-specific mortalities
    and tail/fin erosion
  • Mechanism of action - stimulation of innate
    immune response, i.e. increased number of
    erythrocytes, macrophages, lymphocytes and
    leucocytes, and enhanced lysozyme activity no
    effect on antibody levels digestive enzymes

Control of Yersina ruckeri biotype 1
  • This biotype is not controlled by the currently
    available vaccines
  • An isolate of Micrococcus luteus was effective
    when fed to the fish as a probiotic
  • Appetite was stimulated
  • The isolate was also effective against
    Lactococcus garvieae and Streptococcus iniae

  • What is the difference between probiotics,
    immunostimulants, and oral vaccines?
  • Health benefits are clearly demonstrated
  • Indirect benefit reduction in use of
    antimicrobial compounds
  • Must ensure that probiotic is harmless and stays
    harmless to the host
  • However, there are market opportunities