DETECTION, ISOLATION AND IDENTIFICATION OF FUSOBACTERIUM GASTROSUIS SP. NOV. COLONIZING THE STOMACH OF PIGS. Fusobacterium gastrosuis sp. nov. isolated from pigs' stomachs

Nine strains of a novel Fusobacterium sp. were isolated from the stomachs of 6-8 months old and adult pigs. The isolates were obligately anaerobic, although they endured 2 hours exposure to air. Phylogenetic analysis based on 16S rRNA and gyrase B genes demonstrated that the isolates showed high sequence similarity with Fusobacterium mortiferum, Fusobacterium ulcerans, Fusobacterium varium, Fusobacterium russii and Fusobacterium necrogenes, but formed a distinct lineage in the genus Fusobacterium. The isolates were also distinguishable from these and other Fusobacterium species by phenotypical characterization. The strains produced indole and exhibited proline arylamidase and glutamic acid decarboxylase activity. They did not hydrolyse esculin, did not exhibit pyroglutamic acid arylamidase, valine arylamidase, α-galactosidase, β-galactosidase, β-galactosidase-6-phosphate or α-glucosidase activity nor produced acid from cellobiose, glucose, lactose, mannitol, mannose, maltose, raffinose, saccharose, salicin or trehalose. The major fatty acids were C16 : 0 and C18 : 1ω9c. DNA-DNA hybridization, fingerprinting and genomic %GC determination further supported the conclusion that the isolates belonged to a new, distinct species. The name Fusobacterium gastrosuis sp. nov. is proposed for the novel isolates with the type strain CDW1(T) (= DSM 101753(T) = LMG 29236(T)). Clostridium rectum should be reclassified as Fusobacterium mortiferum since characterization performed for both species in this study revealed no differences.