Type-species and indeed only species of the Streptobacillus genus, a member of the Bacteroidaceae family, streptobacilli are extremely pleomorphic. Gram-negative organisms the shape of which varies from short rods to long interwoven filaments which may fragment into chains of bacilli or cocco-bacilli. Monilia-like swellings of the filaments may occur. Poorly viable on culture, which needs serum media and possibly anaerobic conditions for primary growth, though classified as an aerobe.
A gram-negative bacillus present in the mouths of rats, mice, and cats. It is transmitted to humans through bites or by ingestion of milk contaminated by rats. It causes one form of rat-bite fever, marked by prolonged fever, skin rash, and generalized arthritis. The infection may be treated with amoxicillin-clavulanate or doxycycline.