Lactic acid bacteria (LAB) were isolated from rotifer cultures in a marine hatchery to search for potential probiotics for marine animals. Fifteen strains were first selected among a total of 55, according to antibacterial activity against Vibrio sp. Among eight strains identified as Lactobacillus casei, four were highly adhesive, suggesting some ability for surface colonization. The other strains were identified as Lactobacillus plantarum, Lactobacillus dextrinicus, and Leuconostoc sp. To validate probiotic potential, Artemia were challenged against pathogenic Vibrio alginolyticus, with or without one of six selected LAB strains. The six strains protected Artemia against the pathogen, to some extent on condition that nutrient enrichment was provided. La. casei BR51 and X2 were preferred, as they were efficient even in the absence of nutrient supply. La. casei X2 was finally selected as candidate probiotic, due to the best growth performances of Artemia, with or without the pathogen.

Animal food sources provide human beings with minerals considerably in adequate quantities. Fish is an indispensable reliable source of nutrients, as aquaculture is a sector that is fast growing and which provides 50% of the world's fish production. However, fish production is hampered by the increasing costs of feeds due to the ever rising cost of fish meal, an integral component of fish feeds. Substituting fish meal with cheap, yet highly nutritious ingredients in fish feeds is therefore paramount. This study investigated the effects of substituting fish meal with adult cricket meal (ACM) and black soldier fly meal (BSFM) on minerals content of extruded fish feeds, where four levels of substitution (0, 25, 50 and 75%) were used. The effect of feed moisture content on minerals was also studied where 20 and 30% feed moisture levels were used. Leaching effects of the pellets were studied as well. The results showed a significant increase (P \ 0.05) in the levels of phosphorus and potassium as the level of fish meal substitution increased from 0 to 75%. On the other hand, iron and sodium levels reduced significantly (P \ 0.05) as the level of fish meal substitution increased. Magnesium content increased with increasing level of substitution with BSFM, but decreased with increasing level of substitution with ACM. Copper, zinc and manganese were not greatly influenced by levels of fish meal substitution. Diets that had zero substitution showed higher leaching effect for most minerals than diets that were substituted with 75% ACM or BSFM. This study found that both ACM and BSFM can be used to substitute fish meal in fish feeds and obtain adequate mineral profile and low leaching effect.

The genus Vibrio is characterized by a large number of species and some of them are human pathogens causing gastrointestinal and wound infections through the ingestion or manipulation of contaminated fishes and shellfish including Vibrio parahaemolyticus and Vibrio alginolyticus. In this study, we reported the phenotypic and molecular characterization of 9 V. parahaemolyticus and 27 V. alginolyticus strains isolated from outbreaks affecting cultured Gilthead sea bream (Sparus aurata L.) and Sea bass (Dicentrarchus labrax) along the Tunisian coast from 2008 to 2009. All isolates were tested for the presence of DNase, caseinase, protease, lipase, amylase, gelatinase, hemolytic activity and antibacterial resistance to different drugs. Randomly amplified polymorphic DNA was used to examine the genetic relatedness among the V. parahaemolyticus and V. alginolyticus strains.

Pathogenic Vibrio species are an important cause of foodborne illnesses. The aim of this study was to describe the occurrence of potentially pathogenic Vibrio species in the final effluents of a wastewater treatment plant and the risk that they may pose to public health. During the 1-year monitoring, a total of 43 Vibrio strains were isolated: 23 Vibrio alginolyticus, 1 Vibrio cholerae, 4 Vibrio vulnificus, and 15 Vibrio parahaemolyticus. The PCR investigation of V. parahaemolyticus and V. cholerae virulence genes (tlh, trh, tdh, toxR, toxS, toxRS, toxT, zot, ctxAB, tcp, ace, vpi, nanH) revealed the presence of some of these genes in a significant number of strains. Intraspecies variability and genetic relationships among the environmental isolates were analyzed by random amplified polymorphic DNA-PCR (RAPD-PCR). We report the results of the first isolation and characterization of an environmental V. cholerae non-O1 non-O139 and of a toxigenic V. parahaemolyticus strain in Tunisia. We suggest that non-pathogenic Vibrio might represent a marine reservoir of virulence genes that can be transmitted between strains by horizontal transfer.

The occurrence of the hemolysin genes, tdh and trh, in Vibrio parahaemolyticus strains isolated from environmental samples collected from various exported seafood products comprising of fishes and shellfish (Mytilus edulis and Crassostrea gigas) or seawater, was studied. Eight strains were confirmed as V. parahaemolyticus by toxR -based polymerase chain reaction and only one strain out of these 8 strains was positive for tdh and trh genes. Toxigenic V. parahaemolyticus isolates are present in Tunisian coastal areas and they may also be present in Tunisian exported seafood products.