A previously healthy 26-year-old male presented to the emergency department (ED) at Vancouver General Hospital with a 2-day history of erythema, pain, and swelling of his left ankle and foot, consistent with uncomplicated cellulitis. Laboratory investigations and blood cultures were obtained in the ED, and the patient was discharged home with a plan to complete a course of intravenous (IV) cefazolin as an outpatient. He was recalled 17 h later when two sets of blood cultures returned positive for gram positive cocci in chains.
On further inquiry, the patient endorsed a 2-week history of mechanical lower back pain, initially precipitated by a wrestling injury. He endorsed 2/10 pain to the left foot at the location of the cellulitis. Review of systems was otherwise unremarkable. The patient remained afebrile with no constitutional symptoms and no lower extremity weakness. There was no known injury to the foot or ankle prior to presentation.
On physical examination, the patient’s initial vital signs were: temperature 36.4C, heart rate 138 bpm, respiratory rate 18, blood pressure 123/62 mmhg, SpO2 94% on room air. The left foot was diffusely erythematous from the distal foot to proximal ankle. The involved area was non-purulent and blanchable. The foot was tender to palpation, but there was no fluctuance or crepitus. Cardiac, respiratory, abdominal, and neurological exams were unremarkable. There were no cardiac murmurs or stigmata of infective endocarditis. The spine was not assessed at this time.
Initial laboratory investigations included complete blood count (CBC), electrolytes, extended electrolytes, creatinine, liver function tests (LFTs). These investigations demonstrated anemia, leukocytosis (primarily neutrophilic), mixed hepatocellular and cholestatic elevation of liver enzymes, and abnormal liver function tests (Fig. 1). X-ray imaging demonstrated no evidence of left ankle and foot fracture or osteomyelitis, with no joint effusion on ankle ultrasound.
The clinical presentation was consistent with bacteremia secondary to cellulitis, and the patient received IV fluid resuscitation and empiric treatment with IV vancomycin. After 35 h, two sets of blood cultures in anaerobic and aerobic bottles speciated as S. canis, and antibiotics were changed to ampicillin 2 g IV every 4 h (Q4H) per recommendation from our infectious diseases team. Speciation of blood cultures prompted further history taking and the patient endorsed occasional contact with a housemate’s dog, but without history of bite or trauma to the foot.
Given the patient’s ongoing back pain, which was present through his admission, both computed tomography (CT) and magnetic resonance imaging (MRI) spine were ultimately performed and suggestive of myositis of the right piriformis (Fig. 2) and right erector spinae (Fig. 3), S1 spinal osteomyelitis, and right sacroiliitis (Fig. 4). There were also multiple small fluid collections, the largest measuring 25 × 19 mm, in the right posterior paraspinal soft tissue. These collections were not amenable to drainage per interventional radiology. Transthoracic echocardiogram (TTE) did not demonstrate infective endocarditis. Both liver enzymes and liver function tests rapidly normalized, consistent with resolution of hypoperfusion in the context of sepsis. Abdominal CT did not demonstrate any underlying liver abscess or other pathology.
Ultimately, blood cultures cleared rapidly after 2 days of treatment with IV ampicillin. The patient’s foot pain, redness, and swelling improved over the course of his 1-week hospitalization, and he was discharged home on the same dose of IV penicillin G with plans to complete a 6-week course. This was administered through an outpatient IV pump. An outpatient MRI was ordered to monitor response to therapy, and follow-up was arranged with the outpatient infectious diseases team.
After discharge, the patient’s course of IV penicillin G was extended to 8 weeks in total due to ongoing back pain. He had a repeat MRI (10 weeks after his previous MRI) which demonstrated improving piriformis muscle inflammation, resolution of piriformis fluid collections, although with ongoing SI joint inflammation. His C-reactive protein (CRP) first normalized 12 weeks after initiation of antibiotics and serial CRPs after stopping antibiotics remained normal. At this point, given resolution of his symptoms, improvement of imaging findings, and normalization of CRP, he was discharged from ongoing follow-up.