Progression of temperature and CRP
lage and a bony break through the posterior
aspect of the ischium. The biopsy obtained
from the necrotic area (Image) consisted of
2ml of purulent fluid that was aspirated and
sent for culture. Culture grew pan-sensitive
salmonella. Fevers continued for another
36 hours. Azithromycin (10mg/kg/day)
was added, for intra-cellular antimicrobial
action. Within 24 hours of starting azithromycin,
the fever curve improved and within
48 hours, she was afebrile. Ambulation improved
with physical therapy, and she was
continued on ceftriaxone and azithromycin
throughout admission. She was discharged
with azithromycin and amoxicillin (100 mg/
kg/day divided three times daily) for a total
of seven weeks.
Discussion
S. aureus is the most common cause of
osteomyelitis in children. A literature review
found, in children with sickle cell disease,
Salmonella causes osteomyelitis over twice
as often as S. aureus. 2 A recent case series
and literature review found that osteomyelitis
caused by Salmonella species in immunocompetent
children without hemoglobinopathies
occurs more commonly in boys,
with no identifiable risk factors for the infection,
with increased complications (41% of
the patients) compared to other organisms. 4
These complications include abscess formation,
relapse despite treatment, and development
of multifocal osteomyelitis. 4 This
was found to be true in our case, where an
abscess developed despite appropriate antibiotic
therapy.
Optimal antimicrobial therapy goes beyond
sensitivities, requiring understanding
the PK/PD. Children ages 1 to 12 years have
an increased volume of distribution and
clearance of antimicrobials compared to adolescents.
This usually necessitates higher
doses at more frequent intervals, comparing
children to adults. Both the age of the patient
and the location of the infection may impact
the efficacy of the chosen antimicrobial
agent. Drug concentrations in the blood are
generally similar to the cancellous or spongy
bone just adjacent to the vasculature. Based
on an adult study, ceftriaxone obtains good
concentrations in the more vascularized
cancellous bone, but very poor (<15%) in
the cortical or compact compartment. One
possible reason for initial treatment failure
could be that ceftriaxone dose was not maximized
to dosing of 100 mg/kg/day and that
the acute infection had sequestered long
enough to form an abscess where the antimicrobial
concentration was not sufficient to
treat in the more cortical compartment.
Studies show that drainage of purulent
fluid is essential to success of treatment
despite appropriate antimicrobial coverage.
In a case report, a previously healthy
17-month-old male developed an abscess
secondary to salmonella and, despite other
surgical drainage attempts, ultimately a
CT-guided drainage was required. There was
never clear abscess formation seen on MRI
in our patient, but purulent fluid was found
during the bone biopsy.
Azithromycin was added to the regimen,
when her fevers did not improve after the CT
guided drainage. Third-generation cephalo-
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Volume 117 • Number 3 SEPTEMBER 2020 • 67