Streptobacillus moniliformis Infection
Streptobacillus moniliformis is a commensal organism that inhabits the nasopharynx of wild, pet, and occasionally laboratory rats. When introduced to laboratory mouse populations, it may result in high morbidity and mortality.
In humans, it is the cause of rat bite fever, transmitted by direct contact or bites, and Haverhill fever, transmitted through contaminated food and water. Rat bite fever, usually acquired through contact with pet rats, is a serious, and sometimes fatal, zoonotic disease.Epizootiology and Pathogenesis
Although S. moniliformis is generally associated with wild rats, natural infection in wild mice with polyarthritis has been documented. Exposure of laboratory mouse populations to infected rats is generally the source of infection. Once infection has been introduced to a mouse population, infection can spread rapidly with high mortality. Following oral inoculation, S. moniliformis can be isolated from submaxillary and cervical lymph nodes within 48 hours, with subsequent bacteremia and development of cervical lymphadenitis. A large number of organisms can be isolated from the blood during this stage. Bacteremia is cleared over the course of weeks, with persistence of infection in joints. Studies in rats have revealed that the organism preferentially localizes to metaphyseal capillaries, with subsequent evolution of arthritis. In experimental studies, B6 mice appeared to be uniquely susceptible to severe illness, whereas BALB/c, C3H/He, CBF1, and B6D2F1 mice were more resistant and DBA/2 intermediate in susceptibility. Although generally considered rare in laboratory mice, several outbreaks of streptobacillosis have been documented in the 1990s.
Pathology
Clinical signs during the acute bacteremic stage of infection include conjunctivitis, cervical lymphadenitis, diarrhea, hemoglobinuria, cyanosis, anemia, weight loss, and high mortality. There are disseminated foci of necrosis and inflammation in liver, spleen, and lymph nodes, with petechial and ecchymotic hemorrhages on serosal surfaces.
Suppurative embolic interstitial nephritis with prominent bacterial colonies may be evident. In one outbreak, teat dermatitis with formation of brown crusts was found in breeding female mice. Some mice, particularly those that survive the acute phase, can develop suppurative polyarthritis, osteomyelitis, cervical abscesses, and subcutaneous abscesses. Arthritis frequently involves the feet and tail. Mice may exhibit limb or tail swelling, spinal involvement, posterior paresis, kyphosis, and priapism. Fetal infection with abortion or resorption has also been seen in infected mouse colonies.Diagnosis
Definitive diagnosis of streptobacillosis is made by isolation from infected tissues, using blood agar. Large numbers of bacteria are present in blood and tissues during the acute bacteremic phase and in abscesses and joints during the chronic phase of infection. Organisms are nonmotile and highly pleomorphic, forming long filamentous forms under ideal growth conditions. Both serology and PCR can supplement diagnostic efforts, but neither method is generally applied to routine diagnostics because of the rarity of infections. Differential diagnoses must include other forms of bacteremic disease, such as pseudomoniasis, coryne- bacterial, staphylococcal, and streptococcal infections, as well as arthritis caused by Mycoplasma and C. kutscheri.
More on the topic Streptobacillus moniliformis Infection:
- Streptobacillus moniliformis Infection: Rat Bite Fever
- Rat Papillomavirus Infection
- Francisella tularensis Infection: Tularemia, “Rabbit Fever”
- BIBLIOGRAPHY FOR BACTERIAL AND FUNGAL INFECTIONS
- BIBLIOGRAPHY FOR BACTERIAL INFECTIONS
- BIBLIOGRAPHY FOR BACTERIAL INFECTIONS