SummaryAlthough the currently most eVective treatment regimens cure about 90% of infections, 10% of patients remain Helicobacter pylori positive. Several factors contribute to treatment failure. These include patient compliance, bacterial resistance to antibiotics, and treatment related issues. Treatment failure leads to the development of bacterial resistance to metronidazole and clarithromycin. Retreatment can be undertaken after considering several diVerent strategies: to repeat the same regimen with full doses of medications and a longer treatment duration, or to choose diVerent regimens to avoid the antibiotic previously used, or to switch to proton pump inhibitor (PPI) based quadruple therapy or ranitidine bismuth citrate (RBC) based triple therapy. In principle, full doses and longer treatment durations are advisable. As retreatment is always diYcult, choosing the best available first line treatment regimen is still the best "rescue" treatment.

Gastric infection with Helicobacter pylori is common in both children and adults, but children are considerably less susceptible to peptic ulcers and other pathological sequelae. As a result, the risk to benefit ratio of diagnostic studies and therapeutic regimens for H pylori in adults are likely different from those in pediatric populations. These guidelines for the management of pediatric H pylori infection, developed by the Canadian Helicobacter Study Group, are designed to identify when the diagnosis and treatment of H pylori may improve patient care. Given the low prevalence of this infection in Canada, it is important to recognize that indiscriminate testing and treatment programs in children are not recommended, and indeed may threaten the optimal care of children. Diagnostic tests should be employed judiciously and be reserved for children who are most likely to derive measurable benefit, such as those likely to have peptic ulcer disease. At this time a test and treat strategy in children cannot be considered prudent, evidence based or cost effective. It is appropriate to limit diagnosis and treatment to children and adolescents in whom H pylori has been identified during endoscopic investigation.

Although the incidence of gastric cancer has declined dramatically in Western countries, the most recent data from the International Agency for Research on Cancer show that it remains the second most common cancer worldwide and caused 628 000 deaths in 1990. The incidence and prevalence of gastric cancer are projected to increase over the next few decades in less developed countries as a result of the increased longevity of H. pylori-infected populations and improved therapies. Gastric carcinogenesis is a multistep and multifactorial process beginning with H. pylori-associated gastritis in most cases. H. pylori infection, together with other environmental factors and individual susceptibility, determine the ®nal risk for the development of gastric cancer. The magnitude of H. pylori infection as a risk factor for gastric cancer in the published H. pylori and

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Extraction of highly charged ions (up to 90+) from a high-energy electron-beam ion trap Rev. Sci. Instrum. 73, 30 (2002); An electron-beam ion trap (EBIT) has just been completed in the Clarendon Laboratory, Oxford. The design is similar to the devices installed at the Lawrence Livermore National Laboratory. It is intended that the Oxford EBIT will be used for x-ray and UV spectroscopy of hydrogenic and helium-like ions, laser resonance spectroscopy of hydrogenic ions and measurements of dielectronic recombination cross sections, in order to test current understanding of simple highly charged ions.