Diagnosis and Treatment

S. moniliformis is an extremely fastidious organism that requires special conditions and culture media to grow. When drawing blood cultures, collect aerobic cultures in a purple-top tube, as the anticoagulant, sodium polyanethol sulfonate, in most aerobic culture bottles inhibits the growth of S. moniliformis. Alert the lab that you suspect the organism, which requires enriched trypticase soy agar or broth, and request that the cultures be held for up to two weeks, as the bacteria grow very slowly.⁴ However, because of the difficulty in confirming diagnosis by culture, the diagnosis is often made by history, and empiric antibiotic treatment should be started immediately due to the high complication and fatality rate. Penicillin is the treatment of choice or doxycycline (as used in my patient) for penicillin-allergic patients.

• DOSING (ADULTS)
  • IV penicillin G: 200,000 units every 4 hours for 5–7 days (can be switched to PO once patient shows clinical improvement)
  • PO penicillin V: 500 mg QID, to complete a 14-day treatment course
  • Doxycycline (for PCN-allergic patients): IV or PO 100 mg BID for 14 days
• DOSING (CHILDREN)
  • IV penicillin G: 100,000–150,000 units/kg/day, divided in 4 doses, up to maximum 8 million units/day, for 5–7 days (can be switched to PO once patient shows clinical improvement)
  • PO penicillin V: 25–50 mg/kg/day, divided in 4 doses, up to maximum 2g/day, to complete a 14-day treatment course
  • Doxycycline (for PCN-allergic patients): 2–4 mg/kg/day IV or PO, divided in 2 doses, for 14 days