Heterogeneity in the Helicobacter pylori vacA and cagA genes: association with gastroduodenal disease in South Africa?
BACKGROUND
Helicobacter pylori infection is universally associated with gastritis, but only sometimes with clinically significant disease. Candidate virulence markers seem to be useful in identifying the pathogenic infections in some populations.


OBJECTIVE
To investigate the association between putative virulence markers and disease in an African population.


METHODS
Fifty nine H pylori strains isolated from dyspeptic patients (11 with peptic ulceration, eight with gastric adenocarcinoma, and 28 with no pathology other than gastritis) were studied for differences in the genes vacA and cagA.


RESULTS
Forty seven (80%) of 59 strains had the vacA signal sequence genotype s1 (one s1a, 46 s1b) and 12 (20%) had subtype s2. vacA mid-region analysis revealed that 40 (68%) strains were vacA m1 and 19 (32%) were m2. All 14 strains from patients with peptic ulceration were vacA s1, in contrast to 23 (66%) of 35 strains from patients with gastritis alone (p<0.01). vacA s2 was found exclusively in patients with gastritis alone (p<0.01). All strains isolated from patients with gastric adenocarcinoma were s1b/m1 (p<0. 005 versus gastritis alone). cagA was detectable in 56 (95%) of 59 isolates. Strains from patients with peptic ulceration (12/13 versus 19/30 with gastritis alone, p=0.05) had the shortest fragment length in the 3' region of cagA, while 4/10 strains from patients with gastric cancer had the longest fragment length in this region (p<0. 02 versus gastritis alone).


CONCLUSIONS
In this study, the vacA s1 genotype, and fragment length of the 3' region of cagA identified isolates associated with significant clinical disease. The vacA s1bm1 genotype seems to be strongly associated with gastric cancer.
Kidd
M
M
GI Clinic and Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town, South Africa.
Lastovica
A J
AJ
Atherton
J C
JC
Louw
J A
JA
D000230:Adenocarcinoma / Q000382:microbiology; D000942:Antigens, Bacterial / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D005756:Gastritis / Q000382:microbiology; D005767:Gastrointestinal Diseases / Q000382:microbiology*; D005838:Genotype; D016480:Helicobacter pylori / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D006801:Humans; D010437:Peptic Ulcer / Q000382:microbiology; D016133:Polymerase Chain Reaction; D013045:Species Specificity; D013274:Stomach Neoplasms / Q000382:microbiology; D014774:Virulence
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C074689:VacA protein, Helicobacter pylori; C080866:cagA protein, Helicobacter pylori