Dr. Emily Bowen presented a great case of salmonella infantis osteomyelitis in patient with sickle cell disease during morning report today.
Salmonella as a cause of osteomyelitis is RARE! These cases predominantly occur in patients with sickle cell or other hemoglobinopathies.
Patients with sickle cell disease have functional hypo-/asplenia from chronic microinfarctions leading to splenic atrophy. They are susceptible to infections with encapsulated organisms (e.g., pneumococcus, meningococcus, and SALMONELLA).
Why are asplenic patients at risk of infections with encapsulated organisms?
- Polysaccharide encapsulated organisms evade the innate immune system (C’ and other opsonins bind less effectively to the capsule –> less effective phagocytosis)
- Effective clearance of these organisms depends on production of pathogen-specific IgM antibodies, which are produced by the spleen
Why salmonella (vs. other encapsulated organisms) and why osteomyelitis?
- Possible hypothesis (courtesy of Drs. Brad Cutrell and Frankie Lee):
- Patients with SSD can have micro-infarctions of the bowel, followed by gut translocation of enteric organisms and bacteremia, followed by seeding of previously damaged/infarcted bone. That combined with diminished immunity and ability to clear infection = perfect storm
Treatment of salmonella osteomyelitis:
- Fluoroquinolones (e.g., ciprofloxacin)
- 3rd generation cephalosporins (e.g., ceftriaxone)