The coccoid forms of Helicobacter pylori. Criteria for their viability.

The fact that Helicobacter pylori can revert to a coccoid form has stimulated speculation about its role in transmission and as a possible cause of reinfection in duodenal ulcer disease. Bismuth subcitrate (32 micrograms/ml), bismuth subsalicylate (64 micrograms/ml), amoxicillin (0.05 micrograms/ml) and erythromycin (4 micrograms/ml) inhibited the growth of H. pylori and stimulated the formation of basically respiring but non-culturable coccoid structures. The presence of polyphosphates as energy and phosphorus source permits a certain level of endogenous metabolism to preserve RNA and DNA, as well as structural components like cell wall, cell membrane and cytoplasma for at least 3 months. However, the applied standard laboratory methods were insufficient for regrowth of H. pylori out of the coccoid form.