Suscettibilita di alcune specie ittiche innovative per Photobacterium damselae subsp. piscicida attraverso challenge.

Photobacterium damselae subsp. piscicida (Ph.d.p.) is the causative agent of Photobacteriosis or fish pasteurellosis. The disease has been described in sea bass (Dicentrarchus labrax), sea bream (Sparus aurata) and grey mullet (Mugil cephalus). The development of some new fish species farming in Sicilian mariculture suggested to evaluate their possible susceptibility to such bacterium. For this reason, experimental challenges were carried out to study the susceptibility to the pathogen in meagre (Argyrosomus regius) (n = 10+ 10 control, medium weight 80 g), dentex (Dentex dentex) (n = 10+ 10 control, medium weight 60 g) and sea bass (n = 10+ 10 control, medium weight 50 g), the latter used as a positive control being known as sensitive species to the agent. Fish were reared in 110 litres tanks, at temperature of 24[degree]C, salinity 38%. The strain 249/I99 was injected i.p. and i.m. using 0.1 ml of bacterial solution 106 ufc/ml. High percentage of mortality was registered even if in different times for each of the three species. Fish were necropsized and sampled for bacteriological and histopathological exams. For bacteriological examination liver, kidney and brain samples were collected. Microbiological results let us to identify Ph.d.p. from all the injected fish. To confirm our findings, a commercial kit agglutination (Bionor) specific against Ph.d.p. was used. Histological exam showed a necrosis characterized by miliary foci in lymphoid organs, mainly spleen and cranial kidney, and sometimes also liver. The findings showed in this report could be considered an experimental evidence of the susceptibility of dentex, a mediterranean species in which spontaneous disease has been reported, moreover it is the first report of the sensitivity of meagre to Ph.d.p.