Factors influencing survival of the entericcontaminants Enterotoxigenic Escherichiacoli and Salmonella enterica(serovar Typhimurium) in comparison to the Autochthonous Pathogen Vibrio parahaemolyticus in marine environments

The presence and persistence of enterotoxigenic Escherichia coli (ETEC) is   poorlyinvestigated in marine habitats. Here we compared ETEC with the more studied fecal contaminant, Salmonella enterica serotype Typhimurium (S. enterica) and the marine bacteria Vibrio parahaemolyticus. All three species of bacteria were culturable on agar plates during 8 weeks of incubation in seawater. However, the culturability of ETEC was positively affected by low temperature whereas V. parahaemolyticus was negatively affected. High-nutrient conditions favored the growth of ETEC but not the other bacteria. When the bacteria were fed to blue mussels, V. parahaemolyticus inhibited the filtration activity and the ingestion was lower than that of the enterobacteria.  On the other  hand,  the mussels were  less  efficient  in eliminating V. parahaemolyticus and an in vitro study showed that the hemocytes of three different species of bivalves were not able to kill this strain of V. parahaemolyticus. The bactericidal capacity of bivalves was seemingly an efficient elimination pathway  forS. enterica and ETEC. This study showed that ETEC in endemic areas should, to the same degree as S. enterica and V. parahaemolyticus, be taken in consideration whenassessing the role of marine environments as a source of enteric infection.