How Genetic Bottlenecks Limit the Spread of Cholera Outbreaks

A new study by the Genomics and Microbial Evolution Group at the Miguel Hernández University of Elche (UMH) together with the Department of Host-Microbe Interactions at St. Jude Children's Research Hospital in Memphis, USA, sheds light on why only certain strains of common bacteria become pandemic pathogens. The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), focuses on Vibrio cholerae, the bacterium that causes cholera. It reveals that the most dangerous form of cholera arises from a specific combination of genes and allelic variants that give it an advantage in the human intestine. This research could lead to new strategies to predict and prevent future cholera outbreaks.

The study involved researchers from UMH and St. Jude Children's Research Hospital, including Mario López Pérez, Professor Salvador Almagro-Moreno, Professor José M. Haro Moreno, and predoctoral researcher Alicia Campos López. By analyzing over 1,840 Vibrio cholerae genomes, the researchers identified eleven distinct phylogenetic clusters, with pandemic strains belonging to the largest cluster. The study suggests that pandemic strains emerge due to unique gene clusters and allelic variations that provide a competitive advantage during intestinal colonization, preventing most environmental strains from becoming human pathogens.

The study reveals that genetic bottlenecks limit the emergence of pandemic V. cholerae clones, requiring a specific genetic background pre-adapted for virulence, the acquisition of key gene clusters, their organization into specific arrangements, and the presence of unique allelic variants. These features grant pandemic clones an advantage in colonizing the human gut. The research could be applied to understand how pathogenic clones emerge from non-pathogenic populations and improve public health preparedness.

Cholera is endemic in areas with poor water and sanitation infrastructure, leading to severe diarrhea and dehydration. The study was supported by the U.S. National Science Foundation and other funding sources.