Vibrio cholerae causes cholera, an acute diarrhoeal disease notorious for its ability to spread in rapid and explosive epidemics. Although this bacterial species is extremely diverse, just two discrete lineages of toxigenic V. cholerae are believed to be responsible for all current and historical cholera pandemics. Much is known about the biology and epidemiology of these pandemic lineages, but less is known about non-pandemic V. cholerae, which appear not to have the ability to cause cholera pandemics, though they may cause sporadic cases or outbreaks of cholera or cholera-like disease. In this talk, I will use genomics to highlight the stark contrasts between pandemic and non-pandemic V. cholerae, using the unique aspects of the 1992-1998 cholera epidemic in Argentina to illustrate these concepts. I will describe the progression of a cholera epidemic in a country which, until 1992, had been free of pandemic cholera for nearly 100 years. I will contrast the densely-sampled V. cholerae from this epidemic with the non-epidemic V. cholerae that were present in Argentina at the same time as the pandemic lineage introduced from overseas. I will also highlight how studying these diverse V. cholerae is informing our understanding of how historical cholera pandemics may have progressed in Argentina. Finally, I will use specific examples of how a combination of population-level genomic analysis and experimental validation can both support and challenge molecular microbiological understanding that has been derived from reference strains of V. cholerae. Taken together, the data presented underline the importance of considering diverse, non-pandemic organisms in conjunction with the aetiological agents of pandemic disease, a principle which can be readily generalised to bacteria other than V. cholerae.
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