Phenotypic and Genotypic Characteristics of Members of the Genus Streptobacillus.

The genus Streptobacillus (S.) remained monotypic for almost 90 years until two new species were recently described. The type species, S. moniliformis, is one of the two etiological agents of rat bite fever, an under-diagnosed, worldwide occurring zoonosis. In a polyphasic approach field isolates and reference strains of S. moniliformis, S. hongkongensis, S. felis as well as divergent isolates were characterized by comparison of molecular data (n = 29) and from the majority also by their physiological as well as proteomic properties (n = 22). Based on growth-independent physiological profiling using VITEK2-compact, API ZYM and the Micronaut system fastidious growth-related difficulties could be overcome and streptobacilli could definitively be typed despite generally few differences. While differing in their isolation sites and dates, S. moniliformis isolates were found to possess almost identical spectra in matrix-assisted laser desorption ionization-time of flight mass spectrometry and Fourier transform infrared spectroscopy. Spectroscopic methods facilitated differentiation of S. moniliformis, S. hongkongensis and S. felis as well as one divergent isolate. Sequencing of 16S rRNA gene as well as functional genes groEL, recA and gyrB revealed only little intraspecific variability, but generally proved suitable for interspecies discrimination between all three taxa and two groups of divergent isolates.

Streptobacillus felis sp. nov., isolated from a cat with pneumonia, and emended descriptions of the genus Streptobacillus and of Streptobacillus moniliformis.

A pleomorphic, Gram-stain-negative, rod-shaped, indole-, oxidase- and catalase-negative, non-spore-forming, non-motile bacterium (strain 131000547(T)) was isolated from the lungs of a cat with pneumonia. On the basis of 16S rRNA gene sequence analyses the strain was assigned to the genus Streptobacillus with 97.6% sequence similarity to the type strain of Streptobacillus moniliformis and 94.6% to that of Streptobacillus hongkongensis. The clear differentiation of strain 131000547(T) from Streptobacillus moniliformis and Streptobacillus hongkongensis was also supported by gyrB, groEL, and recA nucleotide and amino acid sequence analysis. DNA-DNA hybridization demonstrated ≤ 19.9% (reciprocal 28.7%) DNA-DNA relatedness between strain 131000547(T) and Streptobacillus moniliformis DSM 12112(T). Physiological data confirmed the allocation of strain 131000547(T) to the family Leptotrichiaceae. Strain 131000547(T) has a unique profile of enzyme activities allowing differentiation from the most closely related species. Within the genus Streptobacillus, isolate 131000547(T) could also unambiguously be separated from Streptobacillus moniliformis and Streptobacillus hongkongensis by both matrix-assisted laser desorption ionization time-of-flight mass spectrometry and Fourier transform-infrared spectroscopy. On the basis of these data, a novel species of the genus Streptobacillus, Streptobacillus felis sp. nov., is proposed with the type strain 131000547(T) ( = DSM 29248(T) = CCUG 66203(T) = CCM 8542(T)). Emended descriptions of the genus Streptobacillus and of Streptobacillus moniliformis are also given.