No abstract

No abstract

The aim of this study was to evaluate the survival responses of two strains of Vibrio splendidus, both in natural and in defined media. For this purpose, freshwater and defined media containing different salinities (3?3-0?9 %) and nutrient concentrations (17-0?005 mg l 21 ) were assayed. The incubation temperatures were established at 4, 10 and 22˚C. The acridine orange staining technique was used for total cell enumeration and the number of viable cells was determined using two direct assays, nalidixic acid and tetrazolium salt reduction and plate spreading. Resuscitation assays of viable but non-culturable (VBNC) cells were conducted. According to the counting procedures employed, at least four different subpopulations were found: (i) active (positive response in both nalidixic acid and tetrazolium assays) culturable cells; (ii) active non-culturable cells; (iii) tetrazolium-salt-responsive non-culturable cells and (iv) non-active (responsive to none of the direct viable assays) non-culturable cells. Long-term survival was found at salinities and nutrient concentrations of seawater environments (3?3 % and 5 mg l 21 or 1 g l 21), whereas the strains entered a VBNC state in freshwater and in brackish (0?9 or 1?6 % salinities) or high nutrient content (17 g l 21 ) defined medium. The recovery of VBNC cells was not achieved.

The presence of a lethal extracellular 39-kDa protease, a virulence determinant of a Listonella pelagia strain which produces vibriosis in turbot, was determined in the extracellular products (ECP) of 33 Vibrionaceae strains. Both immunological and enzymatic techniques distinguished this specific protease from other Vibrionaceae proteins. It was detected in 15% (5/33) of the ECPs assayed belonging to strains of the Vibrio splendidus-V. lentus related group isolated in Galician aquaculture systems (NW Spain). As these strains were associated with diseased octopus and cultured turbot, were able to colonize the internal organs of fish and produced a lethal ECP for fish, they are a potential risk for the health of reared aquatic organisms.

No abstract