First isolation of Photobacterium damselae ssp. damselae from cultured redbanded seabream, Pagrus auriga Valenciennes, in Spain.

Redbanded seabream, Pagrus auriga Valenciennes (Sparidae), has a wide geographical distribution and a very important commercial value in European countries. Recently, this species has been successfully cultured in the C.I.F.P.A. El Toruño (El Puerto de Santa Maria, Cadiz, Spain) as a result of extensive studies on its reproductive cycle, nutrition and growth (Prieto, Cañavate & Cardenas 2003). However, as a consequence of this intensive culture, two disease outbreaks with moderate mortality rates have been recorded. Photobacterium damselae ssp. damselae is an autochthonous inhabitant of both estuarine and marine waters (Ghinsberg, Drasinover, Sheinberg & Nitzan 1995). This bacterial species comprises strains that produce skin ulcers and haemorrhagic septicaemia in a wide range of fish species, and, in addition, it may be a primary pathogen for mammals, including humans (Fouz, Larsen, Nielsen, Barja & Toranzo 1992; Shin, Shin, Suh, Ryang, Rew & Nolte 1996). Although the pathogenicity to mammals constitutes one of the main characteristics to differentiate this subspecies from P. damselae ssp. piscicida (Fouz, Toranzo, Marco-Noales & Amaro 1998), they also differ in important biochemical and physiological traits, as well as in host specificity (Magariños, Toranzo & Romalde 1996). In contrast to P. damselae ssp. piscicida, which is serologically homogeneous, at least four serotypes of P. damselae ssp. damselaehave been recognized (Fouz et al.1992). In the present study, P. damselae ssp. damselae has been isolated from two epizootic outbreaks affecting cultured redbanded seabream. The characterization of the bacterial isolates was performed on the basis of phenotypic characteristics compared with reference strains of both the subspecies of P. damselae. In addition, enzymatic properties of the extracellular products and the susceptibility pattern to several antimicrobials were established. Diseased fish were anaesthetized with MS-222 in sea water (Sigma Chemical Co., St Louis, MO, USA) at a final concentration of 65 mg mL prior to sampling for microbial isolation. Samples were collected from eyes, spleen, liver and kidney, and seeded on tryptic soy agar and broth (Difco Lab., Detroit, MI, USA) supplemented with 1.5% NaCl (TSAS, TSBS), marine agar (Difco), thiosulphatecitrate-bile salt-sucrose agar (TCBS; Difco), and TCBS supplemented with 1.5% NaCl (TCBS-1). The inoculated media were incubated at 22 C for 2–5 days. All the isolates were subjected to taxonomical analysis according to Bergey’s Manual of DeterminJournal of Fish Diseases 2006, 29, 175–179