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Infection and Immunity, March 2000, p. 1507-1513, Vol. 68, No. 3
Division of Geographic Medicine and
Infectious Diseases, Tufts-New England Medical Center, Tufts University
School of Medicine, Boston, Massachusetts
02111,1 and Faculty of Pharmaceutical
Sciences, Okayama University, Okayama,
Japan2
Received 12 October 1999/Returned for modification 12 November
1999/Accepted 29 November 1999
Vibrio mimicus differs from Vibrio cholerae
in a number of genotypic and phenotypic traits but like V. cholerae can give rise to diarrheal disease. We examined clinical
isolates of V. mimicus for the presence of CTX
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Infectious CTX
and the Vibrio Pathogenicity
Island Prophage in Vibrio mimicus: Evidence for Recent
Horizontal Transfer between V. mimicus and V. cholerae
, the
lysogenic filamentous bacteriophage that carries the cholera toxin
genes in epidemic V. cholerae strains. Four V. mimicus isolates were found to contain complete copies of CTX
.
Southern blot analyses revealed that V. mimicus strain PT5
contains two CTX prophages integrated at different sites within the
V. mimicus genome whereas V. mimicus strains
PT48, 523-80, and 9583 each contain tandemly arranged copies of CTX
.
We detected the replicative form of CTX
, pCTX, in all four of these
V. mimicus isolates. The CTX prophage in strain PT5 was
found to produce infectious CTX
particles. The nucleotide sequences
of CTX
genes orfU and zot from V. mimicus strain PT5 and V. cholerae strain N16961 were
identical, indicating contemporary horizontal transfer of CTX
between these two species. The receptor for CTX
, the toxin-coregulated pilus, which is encoded by another lysogenic filamentous bacteriophage, VPI
, was also present in the
CTX
-positive V. mimicus isolates. The nucleotide
sequences of VPI
genes aldA and toxT from
V. mimicus strain PT5 and V. cholerae N16961
were identical, suggesting recent horizontal transfer of this phage between V. mimicus and V. cholerae. In V. mimicus, the vibrio pathogenicity island prophage was integrated
in the same chromosomal attachment site as in V. cholerae.
These results suggest that V. mimicus may be a significant
reservoir for both CTX
and VPI
and may play an important role in
the emergence of new toxigenic V. cholerae isolates.
*
Corresponding author. Mailing address: Division of
Geographic Medicine and Infectious Diseases, Tufts-New England
Medical Center, Tufts University School of Medicine, 750 Washington
St., Boston, MA 02111. Phone: (617) 636-7618. Fax: (617) 636-5292. E-mail: matthew.waldor{at}es.nemc.org.
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