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To determine the source of Streptobacillus notomytis bacteremia in a woman in Japan with signs of rat-bite fever, we examined rat feces from her home. After culture and PCR failed to identify the causative organism in the feces, next-generation sequencing detected Streptobacillus spp., illustrating this procedure's value for identifying causative environmental organisms.

An indole-, oxidase- and catalase-negative, non-motile bacterium, strain OGS16T, was isolated from an oral swab of a feral black rat (Rattus rattus) in 2007 in Japan. It stained Gram-negative and had pleomorphic, rod-shaped, non-spore-forming cells. Based on 16S rRNA gene sequence analyses, strain OGS16T was assigned to the genus Streptobacillus, with 16S rRNA gene sequence similarities of 99.3, 99.0, 98.6 and 95.5% to the type strains of Streptobacillus moniliformis, Streptobacillus notomytis, Streptobacillus felis and Streptobacillus hongkongensis, respectively. Strain OGS16T could also be differentiated clearly from other species of the genus Streptobacillus by rpoB, groEL and recA nucleotide and deduced amino acid sequence analysis. DNA-DNA relatedness as obtained by average nucleotide identity was 89.10% between strain OGS16T and Streptobacillus moniliformis DSM 12112T. Chemotaxonomic and physiological data for strain OGS16T were congruent with results for other closely related members of the family Leptotrichiaceae, represented by highly similar enzyme profiles and fatty acid patterns. MALDI-TOF MS analysis also proved suitable in discriminating strain OGS16T unequivocally from all currently described taxa of the genus Streptobacillus. On the basis of these data, we propose the novel species Streptobacillus ratti sp. nov., with the type strain OGS16T (=JCM 31098T=DSM 101843T). The G+C content of the DNA of the type strain is 25.9 mol% and the genome size is 1.50 Mbp.

Streptobacillus moniliformis is an etiological agent of rat-bite fever and Haverhill fever in human infection. As the currently available methods for identifying the causative bacteria are not satisfactory, we attempted to establish them by PCR using newly designed primers for the 16S rRNA gene of S. moniliformis. We then determined the prevalence of Streptobacillus spp. in two species of feral rats that inhabit an urban region in Japan, because information on the prevalence of the bacteria in feral rats is obscure. The use of PCR with newly designed primers showed that an extremely high proportion of R. norvegicus harbored the bacteria (61/66, 92%), whereas the prevalence was only 58% in R. rattus (30/52). The nucleotide sequence analysis of the 16S rRNA gene of Streptobacillus spp. isolated from oral swabs of feral rats showed at least two different types of bacteria among isolates from R. norvegicus and R. rattus.

To determine the source of Streptobacillus notomytis bacteremia in a woman in Japan with signs of rat-bite fever, we examined rat feces from her home. After culture and PCR failed to identify the causative organism in the feces, next-generation sequencing detected Streptobacillus spp., illustrating this procedure's value for identifying causative environmental organisms. [ABSTRACT FROM AUTHOR]