Biology Reference
In-Depth Information
the pathogen Vibrio P cannot produce siderophores, it had a competitive
disadvantage against the probiont. The same effect was obtained when
the bacterial siderophore deferoxamine was added, thus reinforcing the
competition for iron hypothesis (Gatesoupe, 1997).
A strain of V. alginolyticus (Ili) was inoculated to white shrimp ( Penaeus
vannamei ) larvae (zoea II stage) and later they were challenged with White
Spot Syndrome Virus (WSSV) (Rodriguez et al., 2007). Survival was
enhanced during the fi rst 52 h post challenge, but fi nal survival rate was
no different than the untreated larvae.
-glucans were also offered alone
and in combination with probiotics; the combination treatment provided
a signifi cant survival of the postlarvae after 292 h. Treated (probiotics
-glucans) larvae were reared until juveniles, challenged with WSSV
and some immunological parameters evaluated. It was found, that
this treatment modifi es the immune response of juvenile shrimps and
infl uences WSSV prevalence and shrimp survival in ponds (Rodríguez
et al., 2007).
Pseudomonadaceae and Aeromonadaceae
Pseudomonas sp. previously identifi ed as Vibrio sp. (strain 11) signifi cantly
protected Chilean scallop ( Argopecten purpuratus ) larvae when they were
immersed for 1 h prior to being challenged with a L. anguillarum -related
(VAR) pathogen at a density of 5 x 10 3 cells/mL (Riquelme et al . , 1997).
This strain, isolated from microalgae, showed an inhibitory activity
against the pathogen with the double-layer method (Dopazo et al . , 1988);
the pathogenicity of the VAR strain is based on digestive tract invasion
and production of exotoxins (Riquelme et al . , 1995). The larvae required a
period of about 6 h to signifi cantly incorporate this strain when exposed
at a density of 10 6 cells/mL (Riquelme et al., 2000). Re-inoculation of the
strain has to be done every 2-3 d to ensure its presence in the bacterial
microbiota of the larvae (Riquelme et al., 2001).
Aeromonas media (strain A199), which displayed bacteriocin-like
inhibitory substances (BLIS) against several pathogens of aquatic
organisms, also protected Pacifi c oyster ( Crassostrea gigas ) larvae when
challenged with V. tubiashii (Gibson et al., 1998). The probiotic strain was
added at a fi nal density of 10 4 CFU/mL and 1 h later, the pathogen at 10 2 ,
10 3 , and 10 5 CFU/mL. After 72-96 h, regardless of the density inoculated
of the pathogen, the larval mortalities were no different than those of the
control larvae (no pathogen added), but were signifi cantly different than
those where no probiont was used (only pathogen). It has been correctly
pointed out that the association between BLIS activity and probiotic activity
is circumstantial (Gibson et al., 1998) and further research is needed.
Search WWH ::

Custom Search