1160. Predictive Factors to Guide Empiric Antimicrobial Therapy of Acute Hematogenous Osteomyelitis in Children
Authors: Hoyer Elisabeth , Joseph Marritta , Kaplan Sheldon L , Vallejo Jesus G , McNeil Jonathon C 
Published: December 2021

Abstract

Background
Acute hematogenous osteomyelitis (AHO) is a serious infection in children. ESPID guidelines recommend empiric therapy with antistaphylococcal β-lactams in regions with a low methicillin-resistant S. aureus (MRSA) prevalence. In areas with a moderate-high prevalence of MRSA, selection of empiric therapy can be more challenging. We sought to examine factors present at the time of admission which may predict etiology and guide treatment in pediatric AHO in a region with endemic MRSA.

Methods
We reviewed admissions with ICD9/10 codes for AHO from 2011-2020 in otherwise healthy children. Patients with chronic infection, open or penetrating trauma, orthopedic hardware in situ, or disease secondary to a contiguous focus were excluded. Medical records were reviewed for clinical and laboratory parameters present on the day of admission.

Results
586 cases were included. An etiology was identified in 76.8% of cases and S. aureus was most commonly identified (66.2%, 19% MRSA, Figure 1). Infection due to Kingella kingae (0.7%) occurred in younger children (p=0.01). Significant differences in presenting features were noted across pathogens, although S. aureus dominated in all sub-groups (Figure 2). Among children with respiratory symptoms at presentation, Group A Streptococcus (GAS, 10.7%), and S. pneumoniae (2.6%, p=0.01) were identified twice as frequently. Among children with reptiles exposure, Salmonella was identified in 10.8% (p=0.04). Multifocal infections and those requiring ICU admission were due to S. aureus in 88% and 97% of cases, respectively; these cases were disproportionately MRSA (36.4%, p=0.01 and 54%, p&lt; 0.001). Both ESR and CRP were higher among MRSA compared to any other pathogen (Figure 3, p&lt; 0.01). A CRP at presentation &gt; 7 mg/dl had a 79.6% sensitivity for MRSA infection with a negative predictive value of 91.5%. Among those with either an ESR &gt; 50 mm/hr or a CRP &gt; 7 mg/dl, an organism was identified in 83.2%

Depiction of the relative frequency of major pathogens among a cohort of 586 cases of acute hematogenous osteomyelitis in children

Depiction of the relative frequency of different organisms in children with AHO with various history, exam and laboratory findings

Scatterplot depicting ESR and CRP levels across major hematogenous osteomyelitis pathogens

Conclusion
Subtle differences in symptoms, history and laboratory parameters can provide clues to etiology in pediatric AHO. A CRP &gt; 7 mg/dl at time of presentation is suggestive of MRSA AHO, and this should be considered when planning empiric therapy. Likewise, the absence of extreme elevation of CRP may serve an antibiotic stewardship role in MRSA endemic regions.

Disclosures
Sheldon L. Kaplan, MD, Pfizer (Research Grant or Support) Jonathon C. McNeil, MD, Agency for Healthcare Research and Quality (Research Grant or Support)Allergan (Grant/Research Support)Nabriva (Grant/Research Support, Other Financial or Material Support, Site PI for a multicenter trial)