[Comparative study of survival Vibrio parahaemolyticus with Escherichia coli and Salmonella typhimurium in seawater].

Abstract

In this work, survival tests are conducted in oligotrophic seawater using pathogenic bacterial strains: Escherichia coli entéroagrégative, Salmonella Typhimurium and Vibrio parahaemolyticus. After 26 days of incubation in seawater, the three bacterial strains are exposed to sunlight for nine hours. Bacterial cells of the three strains, recovered at the end of the experiment by centrifugation were tested for their sensitivity to antibiotics and their enzymatic and metabolic profile (API 20E and 20NE). The results showed a decline in the culturability of ascending chronological order: first enteroaggregative Escherichia coli (T90 = 7 days), followed by Salmonella Typhimurium (T90 = 12 days) and finally Vibrio parahaemolyticus (T90 = 43 days). Vibrio parahaemolyticus strain showed better survival under seawater conditions before and after exposure to sunlight compared to other strains tested. On the other hand, the most reduced survival time is observed for Escherichia coli, which then becomes inadequate to predict halophilic pathogenic bacteria. Also, we noted that the solar radiation in this study would be the most important factor affecting the survival of three bacterial strains incubated in oligotrophic seawater. Changes of the enzymatic and metabolic profile are more pronounced in Escherichia coli and Salmonella, which reflect a form of resistance and a response to the passage in a hostile environment. However, the rate of antibiotic susceptibility is more apparent in Vibrio (100%) compared to the wild type Escherichia coli (60%) although the latter has completely lost its power to cultivate. This result underlines the relationship between the antibiotics resistance power of VNC cells and the history of the bacterial strain.