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.

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

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 werevacA 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).

CONCLUSION In this study, thevacA s1 genotype, and fragment length of the 3′ region of cagA identified isolates associated with significant clinical disease. ThevacA s1bm1 genotype seems to be strongly associated with gastric cancer.