Comparative Survival and the Cold-Induced Gene Expression of Pathogenic and Nonpathogenic Vibrio Parahaemolyticus from Tropical Eastern Oysters during Cold Storage

Abstract

Expression of the regulatory stress <i>rpoS</i> gene controls the transcription of <i>cspA</i> genes, which are involved in survival and adaptation to low temperatures. The purpose of this study was to assess the growth kinetics of naturally occurring <i>V</i>. <i>parahaemolyticus</i> in shellstock oysters and in vitro and the cold-shock-induced expression of the <i>rpoS</i> and <i>cspA</i> gene response in vitro during postharvest refrigeration. Naturally contaminated eastern oysters (<i>Crassostrea virginica</i>) and pathogenic (<i>Vp-tdh</i>) and nonpathogenic (<i>Vp-tlh</i>) isolates were stored at 7 ± 1 °C for 168 h and 216 h, respectively. The regulatory stress (<i>rpos</i>) and cold-shock (<i>cspA</i>) gene expressions were determined by reverse transcription PCR. At 24 h, the (<i>Vp-tdh</i>) strain grew faster (<i>p</i> < 0.05) than the (<i>Vp-tlh</i>) strain in oysters (λ = 0.33, 0.39, respectively) and in vitro (λ = 0.89, 37.65, respectively), indicating a better adaptation to cold shock for the (<i>Vp-tdh</i>) strain in live oysters and in vitro. At 24 h, the (<i>Vp</i>-<i>tdh</i>) strain <i>rpoS</i> and <i>cspA</i> gene expressions were upregulated by 1.9 and 2.3-fold, respectively, but the (<i>Vp-tlh)</i> strain <i>rpoS</i> and <i>cspA</i> gene expressions were repressed and upregulated by -0.024 and 1.9-fold, respectively. The <i>V</i>. <i>parahaemolyticus</i> strains that were isolated from tropical oysters have adaptive expression changes to survive and grow at 7 °C, according to their virulence.