Ultrastructural observation of Helicobacter pylori in glucose-supplemented culture media.

Helicobacter pylori in the human gut can be divided morphologically into spiral and coccoid forms. The spiral form is known to change into the coccoid form in culture in vitro. The ultrastructural changes and culturability of H. pylori were studied in medium supplemented with different concentrations of glucose. H. pylori ATCC 43504(T) was cultured in liquid medium containing 10 % heat-inactivated horse serum supplemented with glucose (at 0, 10, 100, 300 and 500 mM) for 7 days. Bacterial ultrastructure and culturability were examined daily. With extended time in culture, the spiral forms had transformed into coccoid forms in all media. The coccoid forms could be further divided into two types, A and B, by electron microscopy. The type A coccoid form had an irregular surface with few flagella and indistinct cytoplasmic membrane. The type B coccoid form had a better-maintained integral membrane structure and was the dominant form in 300 mM glucose-supplemented medium. The highest culturability was obtained using 300 mM glucose-supplemented medium. Based on observations of ultrastructural changes in relation to the culturability data, the coccoid forms could be categorized into three stages: dying, viable but non-culturable and proliferating organisms. The optimal glucose concentration for H. pylori culture in this liquid medium culture experiment was approximately 300 mM.