Genetic Studies of a Helicobacter pylori Cytotoxin, Vacuolating Toxin
碩士 === 國立清華大學 === 生命科學系 === 86 === Two virulence factors encoded by the cytotoxin-associated gene (cagA) and the vacuolating cytotoxin gene (vacA) of Helicobacter pylori (H. pylori) are known to be associated with gastroduodenal pathologic...
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Other Authors: | |
Format: | Others |
Language: | zh-TW |
Published: |
1998
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Online Access: | http://ndltd.ncl.edu.tw/handle/60237895916787648329 |
Summary: | 碩士 === 國立清華大學 === 生命科學系 === 86 === Two virulence factors encoded by the cytotoxin-associated gene
(cagA) and the vacuolating cytotoxin gene (vacA) of Helicobacter
pylori (H. pylori) are known to be associated with
gastroduodenal pathologic conditions. cagA and vacA were
characterized in 173 H. pylori isolates from Taiwanese patients
by PCR. Genotypes of vacA in 119 H. pylori isolates were
characterized by use of PCR-based typing method. The genetic
variation of mid-vacA was further analyzed by PCR-based
restriction fragment length polymorphism (RFLP). The 0.73-kb
middle region of vacA in four Taiwanese isolates and 0.43-kb C-
terminal region in two Taiwanese strains were sequenced.
Nighty-eight percent strains were characterized as cagA+. All
vacA signal peptides were s1a type. In mid-region, greater than
80% strains were identified as m2 type. About 17% strains were
m1T and two strains were typed as m1Tm2 chimeric type. DNA
sequence analysis of the 0.73-kb mid-region showed that two
Taiwanese m2 strains were highly homologous to a Western strain
Tx30a (96% identity), and that two m1T strains were nearly
identical to two m1 Japanese strains (>97% identity). The s1a/
m1T strains were shown more associated with peptic ulceration
than s1a/m2 (p< 0.05). HaeIII RFLP analysis of the 2.0-kb PCR-
amplified vacA fragment from 89 Taiwanese isolates revealed 28
distinct patterns. Each RFLP was associated with one specific
vacA middle type. Further HaeIII RFLP analysis of the 2.4-kb
ureA-ureB segment from isolates in 4 popular vacA RFLPs revealed
a high polymorphism in this locus. Thirteen new ureA-ureB RFLPs
were observed compared with 6 patterns previously published.
High prevalence of cagA+ and s1a strains suggested cagA
phenotype and vacA signal sequence could not be used as markers
of high-risk patients in Taiwan. The vacA polymorphisim might
be associated with increased virulence and thus with severity of
clinical symptoms.
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