MOLECULAR-GENETIC PROPERTIES OF VIBRIO CHOLERAE EL TOR STRAINS CIRCULATING IN AFRICA

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Cholera remains a significant public health concern, particularly in Africa.
• The 7th cholera pandemic (1985-2012) has seen evolving strains impacting the continent.
• Understanding the genetic makeup of circulating Vibrio cholerae is vital for effective control.

Purpose of the Study:

• To investigate the genetic diversity and phylogenetic relationships of cholera strains in Africa.
• To identify the origins and evolutionary dynamics of pandemic strains affecting African populations.
• To assess the implications of genetic variation on virulence and drug resistance.

Main Methods:

• Whole genome sequencing of 30 clinical cholera strains from Africa (1985-2012).
• Single Nucleotide Polymorphism (SNP) analysis of 53 strains, including African and Southeast Asian isolates.
• Phylogenetic analysis to establish evolutionary relationships between strains.

Main Results:

• Extensive genetic diversity was observed among African cholera strains.
• Newer variants, originating from Southeast Asia through gene acquisition and genome alteration, are causing current epidemics.
• Phylogenetic analysis revealed links between most African and Asian strains, with some potentially endemic African strains identified.
• Significant variation in virulence and drug resistance was noted among the studied strains.

Conclusions:

• Current cholera epidemics in Africa are fueled by genetically diverse and evolving strains with origins in Southeast Asia.
• The identified genetic diversity, varying virulence, and drug resistance necessitate ongoing molecular surveillance of cholera agents in Africa.
• Understanding these evolutionary patterns is key to developing targeted interventions and improving public health strategies against cholera.