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Journal of Clinical Microbiology, November 1998, p. 3317-3322, Vol. 36, No. 11
Department of Microbiology, VTEC Reference
Laboratory, Academisch Ziekenhuis Vrije Universiteit Brussel,
Brussels, Belgium
Received 26 March 1998/Returned for modification 23 June
1998/Accepted 20 August 1998
The sequence of a verocytotoxin 2 (VT2) variant gene that was
untypeable by the B subunit PCR and restriction fragment length polymorphism analysis (PCR-RFLP) method described by Tyler et al.
(S. D. Tyler, W. M. Johnson, H. Lior, G. Wang, and K. R. Rozee, J. Clin. Microbiol. 29:1339-1343, 1991) was determined and
compared with published sequences. It was highly homologous to two
recently reported VT2 variant sequences. The PCR-RFLP method described by Tyler et al. was extended to include these new sequences. New VT2
variants were identified in 65 of 359 VT-producing Escherichia coli (VTEC) with newly designed primers (VT2-cm and VT2-f) and were characterized as well by restriction analysis of the amplification products obtained with another VT2-specific primer pair (VT2-e and
VT2-f). The VT genes harbored by 64 of these isolates proved to be
untypeable by Tyler's PCR-RFLP method because no amplification was
obtained with the primers used with this method (VT2-c and VT2-d). The
last isolate harbored the new variant gene in addition to VT2vh-a. None
of the isolates harboring these new toxin genes belonged to serogroups
O157, O26, O103, O111, and O145. All 65 isolates were negative for the
eaeA gene and were significantly less frequently
enterohemolytic or positive for the enterohemorrhagic E. coli (EHEC) virulence plasmid than non-O157 VTEC isolates
harboring other VT2 genes. They were also less frequently isolated from patients with EHEC-associated symptoms. The extended PCR-RFLP typing
method is a useful tool to identify less-virulent VTEC isolates and for
VT genotyping in epidemiological studies with non-O157 strains.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of New Verocytotoxin Type 2 Variant
B-Subunit Genes in Human and Animal Escherichia coli
Isolates
*
Corresponding author. Mailing address: Department of
Microbiology, AZ-VUB, Laarbeeklaan 101, B-1090 Brussels, Belgium.
Phone: 32 2 477 50 02. Fax: 32 2 477 50 15. E-mail:
labomicro{at}az.vub.ac.be.
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