Effects of Salinity and Temperature on Long-Term Survival of the Eel Pathogen Vibrio vulnificus Biotype 2 (Serovar E)

Abstract

Vibrio vulnificus biotype 2 (serovar E) is a primary eel pathogen. In this study, we performed long-term survival experiments to investigate whether the aquatic ecosystem can be a reservoir for this bacterium. We have used microcosms containing water of different salinities (ranging from 0.3 to 3.8%) maintained at three temperatures (12, 25, and 30°C). Temperature and salinity significantly affected long-term survival: (i) the optimal salinity for survival was 1.5%; (ii) lower salinities reduced survival, although they were nonlethal; and (ii) the optimal temperature for survival was dependent on the salinity (25°C for microcosms at 0.3 and 0.5% and 12°C for microcosms at 1.5 to 3.8%). In the absence of salts, culturability dropped to zero in a few days, without evidence of cellular lysis. Under optimal conditions of salinity and temperature, the bacterium was able to survive in the free-living form for at least 3 years. The presence of a capsule on the bacterial cell seemed to confer an advantage, since the long-term survival rate of opaque variants was significantly higher than that of translucent ones. Long-term-starved cells maintained their infectivity for eels (as determined by both intraperitoneal and immersion challenges) and mice. Examination under the microscope showed that (i) the capsule was maintained, (ii) the cell size decreased, (iii) the rod shape changed to coccuslike along the time of starvation, and (iv) membrane vesicles and extracellular material were occasionally produced. In conclusion, V. vulnificus biotype 2 follows a survival strategy similar to that of biotype 1 of this species in response to starvation conditions in water. Moreover, the aquatic ecosystem is one of its reservoirs.

An indirect immunofluorescent antibody technique for detection and enumeration of Vibrio vulnificus serovar E (biotype 2): delevopment and applications

“…The fact that starved and VBNC cells were equally stained by all antisera employed (including the ones obtained against stationary phase‐grown cells and crude LPS) shows that these cells maintain detection‐specific antigens, as suggested in previous studies ( Biosca et al 1996 ; Marco‐Noales et al . 1999 ).…”

“…Polyclonal antibodies against stationary phase‐grown cells, crude lipopolysaccharide (LPS), starved cells and VBNC cells of serovar E had previously been obtained and their serological specificity determined ( Biosca et al 1996 ; Marco‐Noales et al . 1999 ).…”

“…Microcosms of sterilized, artificial seawater (ASW) and unsterilized, natural, coastal seawater from the Mediterranean Sea were prepared as previously described ( Marco‐Noales et al . 1999 ).…”

INFLUENCE OF STARVATION, TEMPERATURE, AND pH ON CULTURABILITY OF ESCHERICHIA COLI O157:H7

“…However, regardless of incubation period (14 days or 300 days), all cells in PBS did not necessarily exhibit coccoid morphology. Change in cell morphology has been observed in both Gram-negative and Grampositive bacteria including Campylobacter jejuni, Enterococcus faecalis, Staphylococcus aureus, and Vibrio vulnificus (Hartke et al 1998;Lazaro et al 1999;Marco-Noales et al 1999;Watson et al 1998). Change in cell morphology may confer a survival advantage, increasing the surface to volume ratio, thereby facilitating the sequestering of nutrients in low-nutrient environments (Byrd 2000).…”

Vibrio vulnificusin aquariums is a novel threat to marine mammals and public health

“…Previous studies have demonstrated that V. vulnificus can survive under nutrient starvation in seawater for years without losing its pathogenic potential for animals and humans (Marco‐Noales, Biosca, & Amaro, ). Thus, it is difficult to eliminate V. vulnificus without scientific measures, and it is necessary to take measures to control the water quality in aquariums.…”