In 1987, an outbreak of pneumonia and meningitis caused by an unknown bacterium occurred in a spa therapy centre. Nine isolates of this pathogen constituted a tight DNA hybridization group. rRNA-DNA hybridization and 16S rRNA sequencing showed that the studied bacteria represented a new branch in superfamily II (= gamma subclass) of the Proteobacteria, close to the genus Oceanospirillum. The new bacterium was highly polymorphic and, in young cultures, had curved Gram-negative cells, motile by polar single flagella. The new bacterium differed from the genus Oceanospirillum by its lacking the NaCl requirement and by reducing nitrate into nitrite, producing indole from tryptophan and producing acid from carbohydrates. The name Balneatrix alpica gen. nov., sp. nov. is proposed for the studied organism. The type strain is strain 4-87 (= CIP 103589).