The impact of global warming on the signature virulence gene, thermolabile hemolysin, of Vibrio parahaemolyticus.

Abstract

Global warming is increasing human exposure to pathogens and has already had an impact on human health. Vibrio parahaemolyticus, a major pathogen causing foodborne illness, accumulates in numerous aquatic organisms and can be affected by environmental stressors such as increased replication errors or DNA damage resulting in point mutations. This could lead to an elevation in the mutation rate, which influences the expansion of Vibrio spp. habitats and the spread of associated diseases. In this study, a total of 241 strains were isolated from aquatic products imported or exported through China Customs between 2005 and 2010. The whole genomes of those strains were sequenced, revealing a highly significant level of genetic diversity. Our analysis identified 27 new sequence types (STs) ranging from ST2950 to ST2976. The global temperature trend since 1950 affects the thermolabile hemolysin gene (tlh) found in all Vibrio parahaemolyticus leading to mutant sites exhibiting similar trends as temperatures rise; seven high-frequency mutation hotspots (A180G, T552G, G657T, T858C, C1062T, A1137G, and T1179C) were identified along with two clinically specific sites (T259C and A951T) that may indicate adaptation over time due to climate change, leading to increased virulence potential for this bacterial species. These results provide insight into the genetics of Vibrio parahaemolyticus and provide a reference for subsequent research, identification, and monitoring efforts related to its spread. IMPORTANCE In this study, Vibrio parahaemolyticus strains were collected from a large number of aquatic products globally and found that temperature has an impact on the virulence of these bacteria. As global temperatures rise, mutations in a gene marker called thermolabile hemolysin (tlh) also increase. This suggests that environmental isolates adapt to the warming environment and become more pathogenic. The findings can help in developing tools to analyze and monitor these bacteria as well as assess any link between climate change and vibrio-associated diseases, which could be used for forecasting outbreaks associated with them.