Tenacibaculum maritimum infection: Pathology and immunohistochemistry in experimentally challenged turbot (Psetta maxima L.)

•Tenacibaculum maritimum can reach organs after both routes of inoculation.•Both routes of inoculation can cause infection and bacteraemia in turbot.•Both routes are suitable to study the pathogenesis of the tenacibaculosis.

Tenacibaculum maritimum is the causative agent of tenacibaculosis, a bacterial disease with a worldwide distribution, which causes important losses in the turbot aquaculture. Despite the importance of this bacterium, little is known about pathogenesis of the tenacibaculosis, pattern of lesions and the portal of entry of T. maritimum. Turbots (Psetta maxima) were experimentally infected with T. maritimum using subcutaneous and intraperitoneal routes of inoculation and samples of skin and internal organs were taken throughout the assay. Fish inoculated by both infection routes suffered a septicaemia but only the subcutaneous inoculation reproduces the disease signs described in natural outbreaks. Bacterial antigen was detected by immunohistochemistry in the internal organs 3 h after infection in fish inoculated by subcutaneous route and 6 h after the inoculation of fish by intraperitoneal route. In summary, both routes of inoculation are able to cause an infection and bacteraemia in the fish. However, subcutaneous inoculation route reproduces the disease in a faster and more reliable way than the intraperitoneal route. Moreover, bacterium spreads along the internal organs easily, but needs a gateway to penetrate in the organism and this portal of entry could be skin.