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Aquaculture is one of the fastest growing sector of food production in the world. Despite the encouraging trends, several constraints have had a negative impact on the growth of aquaculture. Diseases are the primary limiting factor in large scale production facilities, where aquatic animals are exposed to stressful conditions. Bacterial diseases are responsible for heavy mortality in both wild and cultured fish and result in serious economic lossess. Prevention and control of diseases have led during recent decades to a substantial increase in the use of veterinary medicines. However, the utility of anti-microbial agents as a preventive measure has been questioned, given the extensive documentation on the development and spread of antimicrobial resistance genes among bacteria. Several mechanisms can be responsible for the acquirement of antibiotic resistances, the main common of which are chromosomal mutation or acquisition of plasmids. Chromosomal mutations cannot be transferred to other bacteria but plasmids can transfer resistance rapidly. Several bacterial pathogens can develop plasmid-mediated resistances: plasmids carrying genes for resistance to antibiotics have been found in marine Vibrio species and they could be laterally exchanged. The concept of biological disease control using probiotics has received widespread attention during the last decade. When looking at probiotics intended for an aquatic usage, it is important to take into account the complex relationship that an aquatic organism has with its direct environment, compared to terrestrial animals. Gram-negative facultative anaerobic bacteria are dominant in fish and shellfish digestive tract, but the intestinal microbiota of aquatic animals may change very rapidly with the ingestion of microorganisms coming from water and food. This is probably the reason why a large number of probiotics developed in aquaculture are bacteria directly originating from the aquatic environment. However, more ‘traditional’ bacterial or yeast species marketed for animal nutrition (Lactobacillus spp., Pediococcus spp., Bacillus spp., and S. cerevisiae) are also used. They can target fish eggs and larvae, fish juveniles and adults, crustaceans, bivalve molluscs and also live food such as rotifers, artemia, or unicellular algae (Kesarcodi-Watson et al., 2008). Growth-promoting effects, through better feed utilisation and digestion, as well as biological control of pathogen colonisation are the most important expected benefits of probiotic applications. Disease outbreaks caused by Vibrio spp. or Aeromonas spp. have been recognised as the most significant constraint on aquaculture production, particularly in the shrimp subsector, where vibriosis is currently one of the main diseases identified. Whereas in vitro, antagonism to pathogens has been clearly demonstrated for a wide range of probiotic strains, in vivo evidence of efficacy is still very scarce. Most probiotics proposed as biological control agents in aquaculture belong to the lactic acid bacteria (Lactobacillus spp. and Carnobacterium spp.), to the genus Vibrio (V. alginolyticus), to the genus Bacillus, or to the genus Pseudomonas, although other genera or species have also been mentioned (Aeromonas and Flavobacterium). Few multinational pharmaceutical companies have introduced commercial preparations into the market as probiotics feed/food supplement in various commercial names as Aqualact, Spilac, Protexin (Verschuere et al., 2000). This chapter will give some examples on how probiotics can be applied to reduce the incidence of diseases usually affecting aquatic animals, including fish, crustaceans and mollusks. Moreover, a brief consideration on the recent approach of prebiotic administration will also be provided.

El objetivo del presente trabajo fue enumerar e identificar cepas probióticas de bifidobacterias y lactobacilos, aisladas de productos lácteos comerciales presentes en el mercado europeo, así como también determinar su habilidad, y la de otras cepas presentes en la colección de bifidobacterias Scardovi de la Universidad de Bologna-Italia (BUSCOB), de consumir compuestos prebióticos comerciales (1% p/p): galactooligosacárido (GOS), fructooligosacárido (FOS), inulina de elevada solubilidad (IES), inulina de alta polimerización (IAP) y otros no convencionales, utilizados comúnmente como espesantes (0,5% p/p): Goma Espina Corona (GEC), Gelatina (G) y Almidón modificado (AM), éstos últimos de origen argentino. El ensayo se realizó adicionando los sustratos a un medio adecuado para cada género, en presencia de un indicador cuyo viraje permitió ver la utilización del sustrato estudio por parte de cada microorganismo. Como control positivo se utilizó glucosa (1% p/p) y el control negativo se inoculó en ausencia de sustrato carbonado. Para el aislamiento y recuento de los microorganismos se utilizaron diferentes medios selectivos, adecuados para cada especie según bibliografía. La identificación se realizó a través de PCR especie-específica, ERIC–PCR y secuenciamiento, en los casos que fue necesario. TPYmupirocina se confirmó como el mejor medio selectivo para las especies de bifidobacterias, mientras que para Lactobacillus casei, L. rhamnosus y L. paracasei todos los medios testeados resultaron adecuados para su enumeración. En el caso de L. acidophilus y L. johnsonii, el medio MRS-pH 5.4 dio mejores resultados. Con excepción de una cepa de Bifidobacterium animalis ssp. lactis aislada de Spega®, los demás productos contenían los niveles de probióticos recomendados (106-107 UFC/g), luego de 20 días de vida útil. FOS, GOS y IES fueron los sustratos fermentados por el mayor número de especies. L. casei Shirota y L. rhamnosus, aislados de los productos Yakult® y Yomo®, respectivamente, sólo crecieron en presencia de GOS. L. rhamnosus SP1 no utilizó ninguno de los sustratos analizados. Ninguna de las cepas de lactobacilos metabolizó GEC ni IAP. Mientras GEC fue fermentada por B. animalis ssp. lactis DSM 10140T y P23, B. longum ssp. longum B1835 y ATCC 15707T, G y AM no promovieron el desarrollo de ninguna de las cepas investigadas. Se concluye la GEC puede ser utilizada no sólo como aditivo espesante, sino también como sustancia con actividad prebiótica potencial, sobre algunas cepas de bifidobacterias

The quality and safety of foods is of outmost importance for governments, industry and consumers. The EU project Pathogen Combat (www.pathogencombat.com) has provided new essential information and methods on how to reduce the prevalence of pathogens across the entire food chain. During the five years, researchers have obtained new results which have been disseminated and tested into SMEs belonging to dairy, poultry, pork and beef and lamb production chain. The unique achievements of Pathogen Combat will be presented. In addition, we will focus on the use of probiotics and prebiotics as an intervention measure to reduce the prevalence of pathogens at farm level. Campylobacter jejuni has now emerged as a leading bacterial cause of food-borne gastroenteritis in humans around the world. Epidemiological studies indicate poultry and poultry products as a significant source of human infection. We evaluated the effects of two probiotic strains and two prebiotic compounds to modulate the gut microbiota of broiler chickens to obtain a competitive reduction of C. jejuni colonization. The experiments workflow counts: faecal samples collection at three different times, samples processing and qPCR analysis. The best strain, resulting from the first treatment, was then microencapsulated, coupled with the best prebiotic compound and fed to broiler chickens as synbiotic mixture. Detection and quantification of the targeted bacterial groups (Bifidobacterium spp., Lactobacillus spp., Campylobacter spp., and C. jejuni) were performed on fecal samples by Real-Time PCR using SybrGreen chemistry. C. jejuni concentration in poultry faeces was significantly (p

Despite significant investment in food safety, the incidence of food-borne disease is still on the rise in the European Union. Probiotic cultures and prebiotics, as additives in animal feed, may be an effective strategy to prevent or reduce the incidence of pathogens in the gastrointestinal tract of food-producing animals, improving food safety and consumer health. Thanks to the EU project Pathogen Combat, new probiotics cultures has been selected for application in animal nutrition. The selected strains were added to the feed of goats and broilers as lyophilized powder or microencapsulated to better resist to harsh environmental conditions. Following 15 days of treatment, the intestinal microbiota was analysed to evaluate the influence of probiotics on the composition of the microbiota and on pathogen presence.