H. pylori (HP) strains isolated from patients with gastric carcinoma (GC) show an increased susceptibility to resveratrol (Res) in vitro

INTRODUCTION. In normal stomachs, HP expresses an adaptive response to low pH levels through urease and several ionic pumps (IPs), which are essential for the maintenance of a proton gradient across membranes. We hypothesized that HP strains from GC may lose certain IPs that help helicobacters to resist to acid (as they live in a hypo-achlorhydric environment) and show a different susceptibility to the antimicrobial activity of anti-oxidants. METHODS. We tested the susceptibility to Res of 6 cagA+ HP strains from GC, and 7 cagA+ and 6 cagA- strains from controls. Res was diluted in broth; bacterial suspensions were added and incubated at 37 °C in microaerobic atmosphere overnight. After subculture on agar and incubation for 3-5 days, plates were examined. Tests were performed in triplicate and repeated twice. MBCs were the mean values, obtained in the various tests, of the lowest Res concentrations in broth whose subcultures on agar gave no growth. Differences were calculated by the t test for independent samples. RESULTS AND DISCUSSION. The MBCs (in µg/ml) of Res (SD) for GC cagA+ strains, and cagA+ and cagA- control strains were respectively 98 (56), 463 (158) and 245 (76) (P<0.001 and P=0.003; GC vs. cagA+ and vs. cagA- controls). The increased susceptibility to Res of the GC strains may be due to the reduced number/expression of IPs that enable the bacteria to maintain normal proton fluxes across membranes and putatively to resist to low pH levels and the antimicrobial activity of substances endowed with scavenging power.