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Journal of Clinical Microbiology, September 1999, p. 2979-2982, Vol. 37, No. 9
Department of Medicine,
Received 30 December 1998/Returned for modification 19 March
1999/Accepted 4 June 1999
Alleles of the vacuolating cytotoxin gene (vacA) of
Helicobacter pylori vary between strains, particularly in
the region encoding the signal sequence (which may be type s1 or s2)
and the midregion (which may be type m1 or m2). Using a PCR-based
typing system developed in the United States, we showed that 36 strains
from Asia and South America were all vacA signal sequence
type s1; 3 were midregion type m1 and 11 were m2, but 22 could not be
typed for the vacA midregion. All strains possessed
cagA (cytotoxin-associated gene A), another virulence
marker. vacA nucleotide sequence analysis showed that
midregion typing failure was due to base substitutions at the primer
annealing sites. Using the new sequence data, we developed two new
PCR-based vacA midregion typing systems, both of which
correctly typed 41 U.S. strains previously typed by the old system and
successfully typed all 36 of the non-U.S. strains. All previously
untypeable strains were vacA m1, other than one m1/m2
hybrid. In summary, we describe and validate a simple PCR-based system
for typing vacuolating cytotoxin (vacA) alleles of H. pylori and show that this system correctly identifies the signal
and midregion types of vacA in 77 strains from Asia and
North and South America.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Simple and Accurate PCR-Based System for Typing Vacuolating
Cytotoxin Alleles of Helicobacter pylori

*
Corresponding author. Mailing address: Department of
Medicine, Division of Gastroenterology, University Hospital, Nottingham NG7 2UH, United Kingdom. Phone: 44 115 9249924. Fax: 44 115 9422232. E-mail: John.Atherton{at}nottingham.ac.uk.
Present address: Facultad de Medicina, Universidad Nacional
Autonoma de Mexico, Mexico City, Mexico.
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