HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplementary data Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Labbate, M. Articles by Stokes, H. W. Search for Related Content PubMed PubMed Citation Articles by Labbate, M. Articles by Stokes, H. W. Agricola Articles by Labbate, M. Articles by Stokes, H. W.

Use of chromosomal integron arrays as a phylogenetic typing system for Vibrio cholerae pandemic strains

¹ Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, Australia
² Department of Biological Sciences, Macquarie University, Sydney, Australia

Correspondence
M. Labbate
mlabbate{at}bio.mq.edu.au

Approximately 200 serogroups of Vibrio cholerae exist, with only two, O1 and O139, responsible for epidemic and pandemic cholera. Strains from these serogroups have evolved from a common progenitor, with lateral gene transfer largely driving their emergence. These strains are so closely related that separation using single- or multi-locus phylogeny has proven difficult. V. cholerae strains contain a genetic system called the integron that is located in the chromosome and that can integrate and excise DNA elements called mobile gene cassettes (MGCs) by site-specific recombination. Large arrays of MGCs are found in V. cholerae strains. For instance, the O1 El Tor strain N16961 contains 179 MGCs. Since integron arrays are dynamic through recombination and excision of MGCs, it was hypothesized that the MGC composition in a given V. cholerae pandemic strain would be useful as a phylogenetic typing system. To address this, a PCR-based method was used to rapidly characterize the MGC composition of V. cholerae arrays. The results showed that the MGC composition of pandemic V. cholerae cassette arrays is relatively conserved, providing further evidence that these strains have evolved from a common progenitor. Comparison of MGC composition between the V. cholerae pandemic strains was also able to resolve the evolution of O139 from a subgroup of O1 El Tor. This level of differentiation of closely related V. cholerae isolates was more sensitive than conventional single-gene phylogeny or multi-locus sequence analysis. Using this method, novel MGCs from an O1 classical strain and an Argentinian O139 isolate were also identified, and a major deletion in the MGC array in all pandemic O139 strains and a subset of O1 El Tor strains was identified. Analysis of sequenced V. cholerae integron arrays showed that their evolution can proceed by rearrangements and deletions/insertions of large portions of MGCs in addition to the insertion or excision of single MGCs.

The GenBank/EMBL/DDBJ accession nos for the sequences reported in this paper are DQ513153–DQ513172 (recA sequences), DQ513176–DQ5131780 (V. cholerae O139 Arg3 gene cassette sequences), DQ513174–DQ513175 (V. cholerae O1 classical Z17561 gene cassette sequences) and DQ513173 (sequence of MGC86F/MGC128R PCR product amplified from V. cholerae V812).