| dc.description.abstract | ABSTRACT
Naturally, Vibrio parahaemolyticus occurs in the microbiota of marine invertebrates,
and has been associated to outbreaks in aquaculture. In some members of the genus
Vibrio, the virulence is increased by the infection of certain lysogenic phages
(lysogenic state), however, it is unknown whether V. parahaemolyticus virulence can
be modulated for the lysogenic conversion. In the present study the effect of
lysogenic conversion on the physiology and virulence of V. parahaemolyticus was
determined. Ten lysogenic phages (named α, 2, E2, S, ESE, 5c, 5s, 5+++, γ, W)
isolated from clam and shrimp culture were used. The lysogenic states were induced
experimentally by direct exposure of V. parahaemolyticus (strain ATCC 17802) to
each phage and evaluated their effect on the hydrophobicity, enzyme production and
use of different carbon sources through standard test. Also the changes in virulence
were evaluated by challenge test in Artemia and shrimp larvae. And the production of
toxins was assessed in a standard test of Artemia nauplii. The phages included in this
study induced changes in the hydrophobicity of V. parahaemolyticus, from zero to
moderate, and changes in the production of enzymes; including lipases and
proteases. Simultaneously, changes in the metabolic profile of use of carbon sources
were recorded. The phages named α, 2 and E2 significantly increased the virulence
of V. parahaemolyticus for Artemia nauplii and the mixture V. parahaemolyticus/γ
phage for shrimp larvae. The damages observed during the challenge test include
lethargy and melanization of the body. The extracellular products produced by the
5+++ lysogen induces signs of damage and significant mortality in Artemia nauplii
(p<0.05), indicating toxins production. Changes in the properties of V.
parahaemolyticus by lysogenic conversion help to explain their variable effect during
shrimp culture. | |
