acriflavine and Fish-Diseases

Edwardsiella tarda is one of the leading marine pathogens that can infect a wide range of cultured marine species. In this study, the acrR-acrAB cluster was cloned from TX1, a pathogenic E. tarda strain isolated from diseased fish. AcrR and AcrAB were found to be involved in resistance against acriflavine and methyl viologen, which positively regulate the expression of acrAB. AcrR negatively regulates its own expression and the expression of the acrAB operon, most likely by interacting with a 24-bp operator site that overlaps the putative promoter of acrA (P(acrA)). The repressive effect of AcrR on P(acrA) could be relieved by acriflavine, methyl viologen, and ethidium bromide, the presence of each of which enhanced transcription from P(acrA). Interruption of the regulated expression of acrR by introducing into TX1 a plasmid that overexpresses acrR affected growth under stress conditions, AI-2 production, and bacterial virulence. In addition, mutational analyses identified a constitutively active AcrR mutant (named N215), which exhibits full repressor activity but is impaired in its ability to interact with the inducer. Overexpression of N215 produced the same kind of but moderately stronger effect on TX1 compared to that produced by overexpression of the wild-type acrR.

Topics: Acriflavine; Animals; Anti-Infective Agents; Bacterial Proteins; Base Sequence; DNA, Intergenic; Drug Resistance, Multiple, Bacterial; Edwardsiella tarda; Ethidium; Fish Diseases; Gene Expression Regulation, Bacterial; Homoserine; Lactones; Membrane Transport Proteins; Molecular Sequence Data; Multidrug Resistance-Associated Proteins; Multigene Family; Paraquat; Repressor Proteins; Virulence

Motile Aeromonas isolated from fish were studied for their virulence in fish in relation to some surface characteristics. The results showed that only the most virulent strains of A. hydrophila used in this study shared a common O antigen, did not agglutinate in acriflavine, settled down after boiling, and were resistant to the bactericidal action of fresh normal mammalian serum. The least virulent strains could not be grouped into this O antigenic group, they did not settle after boiling, and were sensitive to the bactericidal effect of serum. It is suggested that agglutination in acriflavine, stability after boiling, and sensitivity to normal fresh serum could be used for screening the Aeromonas isolates for virulence in fish.

Topics: Acriflavine; Aeromonas; Animals; Antigens, Bacterial; Bacterial Infections; Blood Bactericidal Activity; Fish Diseases; Hot Temperature; Salmonidae; Serotyping; Trout

Prevention and treatment of aquarium fish diseases is described. A variety of husbandry factors may predispose to disease development and these should always be considered. Any treatment should first be tried on a small sample of fish as toxicity does vary between species.

Topics: Acriflavine; Animals; Coloring Agents; Copper; Ectoparasitic Infestations; Ethylene Glycols; Fish Diseases; Fishes; Formaldehyde; Housing, Animal; Leeches; Methylene Blue; Protozoan Infections; Protozoan Infections, Animal; Quaternary Ammonium Compounds; Sodium Chloride; Trichlorfon