Phenotypic, molecular, and phylogenetic properties of Vibrio cholerae causing endemic cholera in Latin America: a follow-up study

Burden

Cholera is life threatening disease that remains one of the major causes of deaths in the developing countries. Although more than 200 serogroups of V. cholerae reported so far, serogroup O1 and O139 are the major pathogenic strains. Serogroup O1 has two biotypes, classical and El Tor. The classical biotype caused first six cholera pandemics in the Ganges Delta of Bay of Bengal and the other parts of the world. The El Tor biotype of V. cholerae initiated the ongoing 7th pandemic in early 1960s. The El Tor biotype was displaced for a short while in late 1992 when an explosive cholera epidemic occurred by V. cholerae O139 synonym Bengal. O139 however, failed to continue as the predominant epidemic strain and thus V. cholerae El Tor continued to cause the ongoing 7th pandemic.

Knowledge gap

A retrospective study on V. cholerae strains isolated between 1991 and 1997 showed that the biotypes Classical, El Tor, and El Tor variants were involved in endemic cholera in Mexico and ET prototype (wild type) were involved in Peru. We are not aware about the present status of cholera bacteria in different parts of Latin America so; a follow-up study on V. cholerae isolated from 1998 to 2012 was designed.

Hypothesis

The V. cholerae strains causing endemic cholera between 1998 and 2012 in Mexico and other countries of Latin America might not be different in terms of biotype, phenotype, molecular, and phylogenetic properties compared with Asia and Africa.

Objectives

The aim of this study is to determine the prevalent sero-biotypes, molecular status and clonal nature of V. cholerae isolated in Mexico and other Latin American countries and compare those characteristics with the strains isolated from Gangetic Bengal and Africa.

Methods

150 V. cholerae strains (both clinical and environmental) which included 89 strains isolated in Mexico, 45 in Peru, 12 in Brazil, and 6 in Guatemala will be analyzed by culture method, serogrouping and antibiogram. V. cholerae strains will also be subjected to detection of marker genes such as ompW, wbeO1, wbfO139, ctxA and ctxB by PCR. Extensive molecular characterizations using multi-locus genome screening and DNA fingerprinting (phylogeny) by PFGE will also be done.

Outcome measures/variables

This study will generate valuable information on nature (clonal types) of cholera bacteria, their transmission patterns world-wide. This is important because updated information on phenotypic, molecular, and phylogenetic characteristics of V. cholerae associated with cholera in Mexico and other Latin American countries are lacking.

The V. cholerae strains causing endemic cholera between 1998 and 2012 in Mexico and other countries of Latin America might not be different in terms of biotype, phenotype, molecular, and phylogenetic properties compared with Asia and Africa.