Drug-resistance mechanisms in Vibrio cholerae O1 outbreak strain, Haiti, 2010

Abstract

To increase understanding of drug-resistant Vibrio cholerae, we studied selected molecular mechanisms of antimicrobial drug resistance in the 2010 Haiti V. cholerae outbreak strain. Most resistance resulted from acquired genes located on an integrating conjugative element showing high homology to an integrating conjugative element identified in a V. cholerae isolate from India.

Figure 1

Genetic organization of the 2010 Haiti Vibrio cholerae O1 integrating conjugative element (ICE), ICEVchHai1. The ICE contained 97,915 bp and 95 open reading frames. Coding sequences were identified and manually annotated by using an in-house modified version of GenDBv2.2 (Center for Biotechnology at Bielefeld University, Bielefeld, Germany, www.cebitec.uni-bielefeld.de/groups/brf/software/gendb_info/index.html). Regions conserved among previously sequenced ICEs are indicated in black, regions of variability in purple, and previously identified hotspots of homologous recombination in pink. Conserved genes involved in conjugation are indicated in orange. Genes associated with antimicrobial drug resistance (floR [chloramphenicol], strAB [streptomycin], sul2 [sulfamethoxazole], and dfrA1 [trimethoprim]) are indicated in red. The complete sequence of ICEVchHai1 has been deposited into GenBank under accession no. JN648379.

Figure 2

Phylogenetic tree illustrating the genetic relatedness between the Haiti integrating conjugative element (ICE) ICEVchHai1 and other ICEs described in Vibrio cholerae (ICEVchBan1, ICEVchBan9, ICEVchInd1, ICEVchInd4, ICEVchInd5, ICEVchMex1, and SXT). Each ICE is listed by an abbreviated name followed by geographic origin and isolation year of the isolate in this analysis. The sequence of ICEVchHai1 was aligned with the other V. cholerae ICE sequences by using the software Progressive Mauve (http://asap.ahabs.wisc.edu/mauve/download.php), and a neighbor-joining phylogenetic tree was constructed by using PHYLIP (PHYLIP [Phylogeny Inference Package] version 3.69; distributed by J. Felsenstein, Department of Genome Sciences, University of Washington, Seattle, WA, USA). Branch lengths indicate the genetic distance between the different ICEs. The ICEVchHai1 showed highest homology (5 single-nucleotide difference) to ICEVchInd5, an ICE first detected in an isolate of V. cholerae O1 in Sevagram, India, in 1994. The ICE sequences in the analysis can be accessed by using the following GenBank accession nos.: Ban1, GQ463139; Ind1, GQ463144; Ind4, GQ463141; Ind5, GQ463142; Mex1, GQ463143; Ban9, CP001485; and SXT, AY055428. The complete sequence of the ICEVchHai1 has been deposited into GenBank under accession no. JN648379. Scale bar indicates nucleotide substitutions per site.