Microbiology
Highly pleomorphic, filamentous, gram-negative rod.
S. moniliformis is the classic organism. There is also S. hongkongensis isolated from 2 human patients, S. felis from the lung of a cat, S. ratti from black rats, and S. notomytis from a spinifex hopping mouse and a human case in Japan from rats (PubMed).
Epidemiology
Rat bites (a cause of rat bite fever along with Spirillum minus). Also known as Haverhill fever, named after a 1926 outbreak in Haverhill Ma (PubMed) from po exposure.
At least 30% can't recall a rat exposure.
Can also get an infection after drinking rat contaminated water or milk.
Syndromes
Incubation is 3-10 days
Fever (often relapsing), rash (mostly on the hands and feet) and polyarticular arthritis. Arthritis may exist without the symptoms of classic rat bite fever: "Asymmetrical polyarticular involvement of the peripheral joints is typical for streptobacillary arthritis. In contrary to streptobacillary rat-bite fever, skin rash and bacteremia are uncommon (PubMed)."
The odd endocarditis.
Treatment
For penicillin-allergic patients streptomycin or tetracycline.
Notes
It is part of the normal respiratory flora of rats and up to 100% of wild and pet rats can carry it.
Curious Cases
Relevant links to my Medscape blog
Last Update: 07/05/18.