Whole-genome sequence analysis of Vibrio cholerae from three outbreaks in Uganda, 2014 - 2016

Abstract

Background: Cholera remains a serious public health problem in Uganda and Africa. The aim of this study was to provide the complete array of antimicrobial resistance genes, integrative and conjugative elements, virulence genes, pathogenicity islands, plasmids, and insertion sequences in the strains. In addition, this study also aimed to provide a single nucleotide polymorphism (SNP) based phylogenetic analysis of the strains. Methods: In the analysis, both Linux and web-based bioinformatics approaches were used to analyze the study sequences. Databases used included; FastQC, MultiQC, Snippy, PANTHER, PATRIC, Unicycler, ISFinder, Center for Genomic Epidemiology pipelines (i.e. MLST, PlasmidFinder, MyDbFinder, and ResFinder), MashTree and IcyTree.  Results: The 10 sequenced strains of Vibrio cholerae were found to carry virulence-associated genes including MakA, ctxA, ctxB, carA, carB, trpB, clpB, ace, toxR, zot, rtxA, ompW, ompR, gmhA, fur, hlyA, and rstR. Also identified were: genes of the Type VI secretion system including vasA-L, vgrG-2, vgrG-3, vipA/mglA, and vipB/mglB; alsD (VC1589), involved in the synthesis of 2,3-butanediol; alsR, involved in the acetate-responsive LysR-type regulation; makA, the flagella-mediated cytotoxin gene; Type VI pilus genes including tcpA-F, tcpH-J, tcpN, tcpP-T, and icmF/vasK; adherence genes acfA-D and IlpA; and quorum sensing system genes luxS and cqsA. Pathogenicity islands identified comprised of VSP-1 and VSP-2, as well as VPI-1 and VPI-2. In addition, strA and B, APH(3'')-I, APH(3'')-Ib, APH(6)-Id, APH(6)-Ic, murA, pare, dfrA1, floR, catB, and catB9 were among the antimicrobial resistance genes found in the sequences. Analysis for SNPs shared among the sequences showed that the sequenced strains shared 218 SNPs and of these, 98 SNPs were missense. Gene enrichment analysis of these SNPs showed enrichment in genes that mediate transmembrane-signaling receptor activity, peptidyl-prolyl cis-trans isomerase activity, and phosphor-relay response regulator activity. Conclusions: This study applied bioinformatics approaches to provide comprehensive genomic analysis of V. cholerae genomes obtained from Uganda.