RESUMEN
The molecular epidemiology of Helicobacter pylori in Africa is poorly documented. From January 2007 to December 2008, we investigated 187 patients with gastric symptoms in one of the main tertiary hospitals in Dakar, Senegal. One hundred and seventeen patients were culture-positive for H. pylori. Polymorphisms in vacA and cagA status were investigated by PCR; the 3'-region of cagA was sequenced, and EPIYA motifs were identified. Bacterial heterogeneity within individuals was extensively assessed by using an approach based on vacA and cagA heterogeneity. Fourteen per cent of H. pylori-positive patients displayed evidence of mixed infection, which may affect disease outcome. Patients with multiple vacA alleles were excluded from subsequent analyses. Among the final study population of 105 patients, 29 had gastritis only, 61 had ulcerated lesions, and 15 had suspicion of neoplasia based on endoscopic findings. All cases of suspected neoplasia were histologically confirmed as gastric cancer (GC). The cagA gene was present in 73.3% of isolates. CagA proteins contained zero (3.7%), one (93.9%) or two (2.4%) EPIYA-C segments, and all were western CagA. Most of the isolates possessed presumed high-vacuolization isotypes (s1i1m1 (57.1%) or s1i1m2 (21.9%)). Despite the small number of cases, GC was associated with cagA (p 0.03), two EPIYA-C segments in the C-terminal region of CagA (p 0.03), and the s1 vacA allele (p 0.002). Multiple EPIYA-C segments were less frequent than reported in other countries, possibly contributing to the low incidence of GC in Senegal.
