Molecular tools in understanding the evolution of Vibrio cholerae

Abstract

Vibrio cholerae, the etiological agent of cholera, has been a scourge for centuries. Cholera remains a serious health threat for developing countries and has been responsible for millions of deaths globally over the past 200 years. Identification of V. cholerae has been accomplished using a variety of methods, ranging from phenotypic strategies to DNA based molecular typing and currently whole genomic approaches. This array of methods has been adopted in epidemiological investigations, either singly or in the aggregate, and more recently for evolutionary analyses of V. cholerae. Because the new technologies have been developed at an ever increasing pace, this review of the range of fingerprinting strategies, their relative advantages and limitations, and cholera case studies was undertaken. The task was challenging, considering the vast amount of the information available. To assist the study, key references representative of several areas of research are provided with the intent to provide readers with a comprehensive view of recent advances in the molecular epidemiology of V. cholerae. Suggestions for ways to obviate many of the current limitations of typing techniques are also provided. In summary, a comparative report has been prepared that includes the range from traditional typing to whole genomic strategies.

Keywords: MLST; MLVA; PFGE; V. cholerae; cholera; molecular fingerprinting; whole genome sequencing.

FIGURE 1

Timeline of cholera epidemiology since 1817. The upper panel shows important scientific advances that have changed the landscape of cholera epidemiology. Pandemics and their putative causative strains are shown in shaded boxes with dashed boarders. The lowermost panels show infrequent outbreaks and their causative strains, with triangles indicating time of outbreaks. This timeline has been adapted from Banerjee et al. (2014). PFGE, pulsed-field gel electrophoresis; RAPD, random amplification of polymorphic DNA; AFLP, amplified fragment length polymorphism; MLST, multi-locus sequence typing; WGS, whole genome sequencing; VNTRs, variable number of tandem repeats; MLVA, multi-locus variable tandem repeat; and MVLST, multi-virulence locus sequencing typing.

FIGURE 2

A brief scheme that includes phenotype based fingerprinting strategies employed in the classification of Vibrio cholerae.

FIGURE 3

A chart of molecular fingerprinting strategies used in epidemiological investigations of V. cholerae.

FIGURE 4

Pie chart showing the number of publications retrieved from the literature database (HighWire and PubMed) that cited corresponding fingerprinting tools employed in the molecular epidemiology of V. cholerae (Data retrieved up to July, 2015).