(New York) -- According to findings from a new animal study, aspirin's harmful effect on the stomach lining is more damaging in the presence of infection from the "ulcer bug", the Helicobacter pylori bacterium that causes ulcers.

Lead study author Dr. N. Yoshida and colleagues from the Kyoto Prefectural University of Medicine in Japan gave aspirin to gerbils experimentally infected with H. pylori, and to uninfected animals. Infected animals had more widespread areas of tissue erosion and bleeding than uninfected animals. Infected animals also had a larger accumulation of white blood cells, called neutrophils. Treatment with anti-neutrophil serum produced a more dramatic reduction in stomach damage in the H. pylori infected animals.

The findings indicate that H. pylori worsens stomach damage from aspirin through mechanisms that include the accumulation of neutrophils. Both aspirin and H. pylori had been known to damage the stomach lining, but how the two factors interacted had previously been unclear.

In a related editorial, Dr. Adrian Schmassmann from KSSW Lucerne in Switzerland notes that the results should be "completed" in a future study by showing that eliminating H. pylori would "reverse the severity of aspirin-induced gastric injury to levels found in uninfected gerbils."