Summary

A Helicobacter pylori-negative young Japanese man with dyspeptic symptoms suffered from a diffuse erosive gastroduodenitis and multiple superficial ulcerations. Histology and electron microscopic examinations on the biopsy specimens revealed the presence of multiple unidentified intralesional and intracellular coccoid microorganisms in the pathological gastroduodenal mucosa. Microaerophilic and anaerobic Gram-negative coccoid and filamentobacillary bacteria were cultured from the gastric aspirate. The triple therapy containing tetracycline for 14 days followed by 4 months treatment with omeprazole resulted in the resolution of the gastroduodenal pathology. The question, therefore, was raised regarding a possible role for the cultured coccoid bacteria in the pathogenesis. 16S rRNA gene sequence analysis of the isolated Gram-negative coccoid bacteria revealed a close relationship with Haemophilus haemolyticus. The unidentified coccoid microorganisms and cultured X and V factors independent coccoid bacteria, however, shared similar phenotypic, microbiological and pathological characteristics to the novel Gram-negative Streptococcaceae: Okadaella gastrococcus.