Tenacibaculum maritimum is the aetiological agent of an ulcerative disease known as tenacibaculosis, which affects a large number of marine fish species in the world and is of considerable economic significance to aquaculture producers. Problems associated with epizootics include high mortality rates, increased susceptibility to other pathogens, high labour costs of treatment and enormous expenditures on chemotherapy. In the present article we review current knowledge on this bacterial pathogen, focusing on important aspects such as the phenotypic, serologic and genetic characterization of the bacterium, its geographical distribution and the host species affected. The epizootiology of the disease, the routes of transmission and the putative reservoirs of T. maritimum are also discussed. We include a summary of molecular diagnostic procedures, the current status of prevention and control strategies, the main virulence mechanisms of the pathogen, and we attempt to highlight fruitful areas for continued research.

The necessary replacement of fish meal with other protein source in diets of commercially important fish has prompted the study of the effect of the inclusion of different vegetable proteins sources on growth performance and on the gastro-intestinal tract. Currently, soybean meal is the primary protein source as a fish meal replacement because of its low price and high availability. Likewise, it is been documented that the ingestion of soybean meal by several fish species, such as salmonids and carp, triggers a type of intestinal inflammation called enteritis. In this paper, we analyzed the effects of the ingestion of soybean meal and two of its components, soy protein and soy saponin, on zebrafish to establish the basis for using zebrafish larvae as a model for fish nutrition. We took advantage of the existence of different transgenic lines, which allowed us to perform in vivo analysis. Our results indicated that larvae that were feed with soybean meal developed a clear intestinal inflammation as early as two day after beginning the diet. Moreover, we determined that is not the soy protein present in the diet but the soy saponin that is primarily responsible for triggering the immune response. These findings support the use of zebrafish screening assays to identify novel ingredients that would to improved current fish diets or would formulate new ones.

Piscirickettsiosis or salmonid rickettsial septicaemia (SRS) caused by Piscirickettsia salmonis constitutes one of the main problems in farmed salmonid and marine fishes. Since the first reports of the disease, it has been successfully isolated and maintained in eukaryotic cell--culture systems, but these systems are time-consuming, the media are costly, and eliminating heavily contaminated host cell debris is difficult. In this report, we describe a marine-based broth supplemented with L-cysteine, named AUSTRAL-SRS broth, that facilitates superior growth of P. salmonis strains. Strains reached an optical density of approximately 1.8 when absorbance was measured at 600 nm after 6 d incubation at 18°C. Several passages (n = 6) did not alter the culture kinetics. We report for the first time the purification of DNA, lipopolysaccharide (LPS) and whole membrane protein obtained from P. salmonis grown in this liquid medium, and thus provide a suitable platform to simplify the preparation of P. salmonis cells for genetic and serological studies. Moreover, the results of the cytopathic effect test showed that P. salmonis grown in AUSTRAL-SRS broth maintained their virulence properties, inducing apoptosis after 3 d. This makes the medium a good candidate for the successful growth of P. salmonis and an excellent basis for the development of low cost vaccines.

Tenacibaculosis occurs due to the marine bacterial pathogen Tenacibaculum maritimum. This ulcerative disease causes high mortalities for various marine fish species worldwide. Several external clinical signs can arise, including mouth erosion, epidermal ulcers, fin necrosis, and tail rot. Research in the last 15 years has advanced knowledge on the traits and pathogenesis mechanisms of T. maritimum. Consequently, significant progress has been made in defining the complex host-pathogen relationship. Nevertheless, tenacibaculosis pathogenesis is not yet fully understood. Continued research is urgently needed, as demonstrated by recent reports on the re-emerging nature of tenacibaculosis in salmon farms globally. Current sanitary conditions compromise the development of effective alternatives to antibiotics, in addition to hindering potential preventive measures against tenacibaculosis. The present review compiles knowledge of T. maritimum reported after the 2006 review by Avendaño-Herrera and colleagues. Essential aspects are emphasized, including antigenic and genomic characterizations and molecular diagnostic procedures. Further summarized are the epidemiological foundations of the T. maritimum population structure and elucidations as to the virulence mechanisms of pathogenic isolates, as found using biological, microbiological, and genomic techniques. This comprehensive source of reference will undoubtable serve in tenacibaculosis prevention and control within the marine fish farming industry. Lastly, knowledge gaps and valuable research areas are indicated as potential guidance for future studies.

Eight bacterial strains isolated from diseased rainbow trout (n=5) and Atlantic salmon (n=3) were characterized by phenotypic and molecular taxonomic methods. The isolates were negative for the Gram-reaction, non-motile, rod-shaped and catalase- and oxidase-positive. Colonies on solid media were yellow, smooth, shiny and circular with regular edges. Growth occurred at 4–28 °C (optimum, 15 °C) and with 0–3 % NaCl (optimum, 0.5 %). Analysis of the 16S rRNA gene sequence allocated the micro-organisms to the genus Chryseobacterium, with Chryseobacterium soldanellicola PSD1-4T and Chryseobacterium soli JS6-6T as their closest relatives (96.9 and 97.1 % sequence similarity, respectively). The levels of DNA–DNA hybridization towards these nearest phylogenetic neighbours were below 17.1 %. The DNA G+C contents of strains VQ-6316sT and VQ-4836s were 32.5 and 32.3 mol%, respectively. The predominant menaquinone was MK-6 and the major fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C17 : 1 ω9c, iso-C17 : 0 3-OH and summed feature 3 (comprising C16 : 1 ω7c and/or C16 : 1 ω7t and/or iso-C15 : 0 2-OH). The eight isolates were classified as representatives of a novel species, Chryseobacterium piscicola sp. nov., with strain VQ-6316sT (=CECT 7357T=DSM 21068T) as the type strain.