Indiana University Infectious Diseases Fellowship
24 Feb,
13 tweets, 5 min read
#idboardreview 50 M unstable housing presents w/ fever, hip & knee pain and swelling. Knee aspirate shows gram negative rod in chains w/ lateral bulbar swelling. Diagnosis? #medEd #idmedEd #IDTwitter 
#Streptobacillus moniliformis, the etiologic agent of rat-bite fever
#Streptobacillus moniliformis highly pleomorphic, filamentous GNR nonmotile, non–acid-fast; may be fusiform & develop lateral bulbar swellings. 2 variants: L form: cell wall deficient nonpathogenic. Spontaneous conversion between 2 forms may be responsible for clinical relapses
Transmission to humans occurs mainly from bites of rats and other rodents. Rats are the dominant natural reservoir of S. moniliformis, which is part of the commensal flora of the upper respiratory tract. The risk for infection after a rat bite appears to be 10%
29% of RBF cases were not associated with an acknowledged bite and were probably acquired by exposure to excreta or saliva when handling an animal
epidemic form of this disease, known as Haverhill fever, is caused by S. moniliformis–contaminated milk. cdc.gov/rat-bite-fever…
#Streptobacillus moniliformis–associated RBF is classically characterized by relapsing fever; maculopapular, petechial, or purpuric rash; and migratory polyarthralgias. The joints most frequently affected are the knees, ankles, elbows, and shoulders
#streptobacillus natural history is one of relapses & remissions, with most cases resolving spontaneously in 2 wks. However, serious complications as endocarditis, myocarditis, pericarditis, systemic vasculitis, meningitis, hepatitis, pneumonia, and focal abscesses may ensue
#streptobacillus extremely fastidious needs microaerophilic conditions to grow. 0.05% sodium polyanethol sulfonate added to most commercial aerobic BC bottles inhibits its growth so grows in anaerobic bottle alone. Grows in 7d trypticase soy agar or broth enriched w/ 20% blood
#streptobacillus treated with penicillin x10-14d. Tetracycline for penicillin allergic pts. Ceftriaxone and clinda may work as well
Reference P&P ID Mandell
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