Molecular-genetic properties of Vibrio cholerae El Tor strains circulating in Africa

Abstract

The review contains some brief information on cholera epidemics in Africa. Comparative analysis of the results of whole-genome sequencing of 30 clinical strains isolated in Africa in different periods of the seventh cholera pandemic (1985–2012) and data from GenBank revealed their great genetic diversity. It is demonstrated that cholera epidemics in Africa, which began in 1970, were caused for about two decades by typical strains of the pathogen brought from India and Bangladesh. Currently, cholera in Africa is caused by new variants of the pathogen, which originated in Southeast Asia as a result not only of the acquisition of new genes due to horizontal transfer but also alterations in the genomes of previously existing pathogenicity and pandemicity islands. SNP analysis of 53 strains circulating in Africa (30 strains), as well as those isolated in Southeast Asia (23 strains), made it possible to establish phylogenetic relations for the majority of African and Asian strains. The issue of the existence of strains which are apparently endemic for Africa is being discussed. The existing genetic diversity of strains with different levels of virulence and drug resistance indicates the need for continuous molecular monitoring of the causative agent of cholera in Africa.