Response of Pasteurella piscicida and Flexibacter maritimus to skin mucus of marine fish

Abstract

ABSTRACT:The antibacterial activity present in the s k~n mucus of turbot Scophthalmus maximus, seabream Sparus aurdtd and seabass Dicentrarchus labrdx against Pasteul-ella piscicida and Flex~bac-ter maritimus was evaluated. Using assays on agar plates, none of the mucus samples from the above fish showed any antibacterial activity against E maritimus isolates. Turbot mucus inhibited the growth of the P piscicida but mucus from seabream and seabass did not. Assays in liquid systems to determine the survival of the above pathogens In the presence of skin mucus corroborated the results obtained by the agar plate method. The bactericidal properties of the mucus were lost after heat treatment at pH 3.5 and all skin mucus samples displayed act~vity against Staphylococcus aureus ATCC 25923, a straln resistant to lysozyme. These findings indicated that thermolabile substances other than lysozyme were responsible for the antibacterial activity in mucus of marine fish. Enzymatic and heat treatments of the mucus also showed that factors other than complement were involved and that the active component(s) was likely a glycoprotein. Regardless of the source of isolation and degree of virulence, all P piscicida and E maritimus strains adhered strongly to the skin mucus of the 3 fish species tested. Taking all of the foregoing results into consideration, it appears that whereas a possible portal of entry for E maritlmus Into the fish body is the skin, in P piscicida another pathway must be involved.

An Overview of the Immunological Defenses in Fish Skin

“…piscicida, and Flexibacter maritimus) for the mucus of different fish species [278,282,283]. However, Magarinos et al [284] demonstrate that the sea bream skin mucus can inhibit the adhesion of Pasteurella piscicida, Flexibacter maritimus, V. anguillarum, and V. damsela.…”

Tenacibaculosis infection in marine fish caused by Tenacibaculum maritimum: a review

“…stress, excess of UV light, lack of sand substrate on the tank), management factors (i.e. high density and poor feeding) and host-related factors (skin surface condition) (McVicar & White 1979, Wakabayashi et al 1984, Chen et al 1995, Magariños et al 1995, Handlinger et al 1997. In these adverse conditions, the systemic disease involving different internal organs became more prevalent (Alsina & Blanch 1993, Cepeda & Santos 2002, Avendaño-Herrera et al 2004b, indicating that Tenacibaculum maritimum has strong virulence mechanisms.…”

“…This pathogen attaches itself strongly to the external skin and mucus of fish which do not contain compounds that inhibits the growth of this bacterium (Magariños et al 1995). The localization of the bacteria within the mucus layer suggests that T. maritimum could be part of the autochthonous populations of the fish skin, and therefore the pathogen can remain in the aquatic environment for a long time, utilizing fish mucus as a reservoir (Avendaño-Herrera 2005).…”

“…Magariños et al (1995) reported that Tenacibaculum maritimum, regardless of its origin and virulence degree, adhered strongly to the skin mucus of 3 fish species, and resisted its bactericidal properties.…”

Tenacibaculosis in aquaculture farmed marine fish

“…A systemic disease can be also established involving different internal organs (Magariños et al, 1995;Pazos et al, 1996;Santos et al, 1999;Avendaño-Herrera et al, 2004a;Toranzo et al, 2005).…”