Virulence of luminescent and non-luminescent isogenic vibrios towards gnotobiotic Artemia franciscana larvae and specific pathogen-free Litopenaeus vannamei shrimp.
OBJECTIVE
This study was conducted to test the virulence of luminescent (L) and non-luminescent (NL) isogenic strains of Vibrio campbellii LMG21363, Vibrio harveyi BB120 (wild type) and quorum-sensing mutant strains derived from the wild type such as Vibrio harveyi BB152, BB170, MM30 and BB886.


RESULTS
The NL strains could be obtained by culturing rifampicin-resistant luminescent strains in the dark under static condition. The virulence of the L and NL strains was tested in gnotobiotic Artemia franciscana larvae challenged with 10(4) CFU ml(-1) of bacteria. All luminescent isogenic tested strains showed higher virulence compared to the NL strains. The virulence of L and NL V. campbellii and V. harveyi BB120 was also tested in specific pathogen-free juvenile shrimp upon intramuscular injection with 10(6) CFU of bacteria. In contrast with Artemia, there was no significant difference in mortality between the groups challenged with L and NL strains (P > 0.05). The non-luminescent strains were not able to revert back to the luminescent state and quorum sensing did not influence this phenotypic shift.


CONCLUSIONS
Luminescent Vibrio strains can switch to a non-luminescent state by culturing them in static conditions. The NL strains become less virulent as verified in Artemia.


CONCLUSIONS
The luminescent state of Vibrio cells in a culture needs to be verified in order to assure maintenance of virulence.
Phuoc
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LH
Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Belgium.
Defoirdt
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T
Sorgeloos
P
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Bossier
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D000818:Animals; D001156:Artemia / Q000382:microbiology*; D015169:Colony Count, Microbial; D007814:Larva / Q000382:microbiology; D008163:Luminescent Measurements; D009026:Mortality; D053038:Quorum Sensing; D014733:Vibrio / Q000472:pathogenicity*; D014774:Virulence