Pathogenicity of Aeromonas hydrophila, previously isolated from kidney of apparently healthy silver carp, was tested in silver carp Hypophthalmichthys molitrix. Trials were also made to control the pathogen in the experimentally infected fish. Before artificial infection the morphological, biochemical and physiological characters of A. hydrophila were studied. The infection was done by intramus...

LuxS/AI-2 quorum sensing is involved in the virulence of many bacterial pathogens, including the fish pathogen Edwardsiella tarda. In a previous study, we identified a small peptide, 5906, which inhibits E. tarda LuxS activity by binding specifically to LuxS in a manner that probably prevents the formation of functional LuxS homodimer. In the present study, using Japanese flounder as the experi...

Lactococcus garvieae is the etiological agent of lactococcosis, an emerging disease which affects several fish species and causes important economic losses both in marine and freshwater aquaculture. Lactococcosis usually happens when water temperature increases over 15°C during the year. Normally, it causes a hyperacute and haemorrhagic septicemia in fish. This paper presents a procedure for pr...

Enteric red mouth disease (also known as Yersiniosis) is one of the most significant bacterial infections in coldwater fish farms that cause significant mortalities and economical losses in the salmonids fish farms, especially in rainbow trout (Oncorhynchus mykiss). ERM is caused by the gram negative pathogen bacteria Yersinia ruckeri that has five O-serotypes (O1, O2, O5, O6 and O7), five oute...

Prophylactic antibiotics in the aquaculture and ornamental fish industry are intended to prevent the negative impacts of disease outbreaks. Research in mice and humans suggests that antibiotics may disturb microbiome communities and decrease microbiome-mediated disease resistance, also known as "colonization resistance." If antibiotics impact fish as they do mice and humans, prophylactic admini...

Dietary thiaminase I is a cause of thiamine deficiency in animals. The physiological significance of thiaminase in the organisms containing this enzyme is not known, nor are the factors causing variation in their thiaminase activity. Tests were performed to evaluate the effect a pathogen might have on thiaminase activity in fish, when analyzed both with a cosubstrate added (CATA tests) and no c...

Toll-like receptors (TLR) recognize the pathogen-associated molecular patterns (PAMPs) and regulate the subsequent immune responses in mammals. We have so far succeeded in finding the 11 types of TLR genes from Japanese flounder (Paralichthys olivaceus). TLR genes have also been found in the genomes of fugu (Takifugu rubripes) and zebrafish (Danio rerio). However, only limited information is kn...

Under intensive aquaculture conditions, fish are exposed to many pathogens, due to that strengthening their immune system is an alternative significant way to reduce mortality rate and disease-related complications. Probiotics are valuable oral nutrition supplements for this purpose. In the present investigation, there were used Koi fish (n=120) with the characteristics of 10±3 Cm in length and...