MedWire News: For patients infected with the stomach ulcer-causing bug Helicobacter pylori, the likelihood of successful eradication following treatment may depend on the particular strain of the bacteria, as well as the extent of the infection, Chinese study results show.

Dr Jian Jun Zhao and colleagues from China-Japan Union Hospital of Ji Lin University in Changchun explain that 1 week of triple therapy with one stomach-acid suppressing drug and two antibiotics is the standard treatment for people infected with Helicobacter pylori.

But they say that, "unfortunately, not all patients can get a good result with triple therapy", with around 10-20% of patients failing to respond to such treatment.

"In some of these patients, treatment failure is due to acquired bacterial resistance to the antibiotics," explain the researchers. However, they add that that there is "little information on whether additional factors other than bacterial resistance may contribute to treatment failure".

To see whether particular strains of Helicobacter pylori influence the effectiveness of triple therapy, the team studied 66 patients with intestinal ulcers who underwent the treatment.

In total, triple therapy successfully eradicated Helicobacter pylori in 57 of these patients.

Analysis revealed that triple therapy was more effective in people infected with the cagA-positive strain of Helicobacter pylori than in those with the cagA-negative strain.

The vacA strain of Helicobacter pylori did not appear to influence the success or failure of triple therapy.

Further analysis showed that high levels of Helicobacter pylori infection and abnormal changes in cells near the ulcer, called intestinal metaplasia, were also associated with an increased risk of triple therapy failure.

"The data confirm the importance of cagA positivity as a predictor of successful eradication. When high Helicobacter pylori colonisation density and intestinal metaplasia are present, therapy appears to be less effective," the researchers conclude in the Journal of Gastroenterology and Hepatology.

They add: "By knowing which patients are more likely to respond, we may then use longer term treatment to perhaps achieve better eradication results."