EFFECT OF LOW-TEMPERATURE ON STARVATION-SURVIVAL OF THE EEL PATHOGEN VIBRIO-VULNIFICUS BIOTYPE-2

At present, no reports exist on the isolation of the eel pathogen Vibr io vulnificus biotype 2 from water samples, Nevertheless, it has recen tly been demonstrated that this biotype can use water as a route of in fection, In the present study, the survival of this pathogen in artifi cial seawater (ASW) microcosms at different temperatures (25 and 5 deg rees C) was investigated during a 50-day period, with biotype 1 as a c ontrol, V. vulnificus biotype 2 was able to survive in the culturable state in ASW at 25 degrees C in the free-living form, at least for 50 days, entering into the nonculturable state when exposed to low temper ature, In this state, this microorganism survived with reduced rates o f activity, showing marked changes in size and morphology. The rate at which cells became nonculturable was dependent on their physiological age, The capsule seems not to be necessary for the survival of biotyp e 2 in aquatic environments as a free-living organism, Culturability r emained the highest on modified salt water yeast extract agar, which i s closer in salt and nutrient composition to ASW than heart infusion a gar, Biotype 2 cells recovered culturability on solid media after an i ncrease of incubation temperature from 5 to 25 degrees C. Culturable c ells of this bacterium maintained infectivity for either eel or mice, while dormant cells seemed to lose their virulence, The former finding suggests that the aquatic environment is a reservoir and vehicle of t ransmission of this pathogen.