Relative Contribution of Blood and Bone Cultures in the Microbiologic Diagnosis of Staphylococcus aureus Osteomyelitis in Children
Methods: Isolates and patients were identified from a prospective S. aureus surveillance study. The database was searched from 4/2012-3/2014 for patients with the diagnosis of osteomyelitis. Medical records were reviewed and data entered on standardized forms. Statistical analyses were performed with STATA 12.
Results: MSSA and MRSA infection occurred in 70 (59.3%) and 48 (40.7%) children (n=118), respectively. MRSA osteomyelitis was associated with intraosseous/subperiosteal abscess (p=0.009) and/or pyomyositis/myositis (p=0.02). Blood cultures (BC) were performed in 111 of 118 (94%) patients and were positive in 61% (68/111). In 33.8% (23/68) of cases, a BC was the only source that that yielded S. aureus. Bacteremia did not differ between MRSA (62%) vs. MSSA (60.6%) osteomyelitis. Surgery was performed in 75.4% (89/118) of patients. Intra-operative cultures were positive in 93.3% (83/89) of cases and in 50.6% (42/83) it was the only positive culture. A bone biopsy was performed by interventional radiology (IR) in 12% of patients (14/118). The IR culture was positive in 78.6% (11/14) of cases and in 36.3% (4/11) it was the only positive culture. In 43 of 50 patients (86%) with a negative BC, bone culture (surgical or IR) led to a change in antibiotic management.
Conclusion: Since 2012 most cases of S. aureus osteomyelitis were caused by MSSA, continuing with a shift in epidemiology at our institution which started in 2007. The majority of patients were bacteremic, however, a bone culture (surgical or IR) played a significant role in the diagnosis and treatment of patients with negative BC. IR bone cultures may be positive for S.aureus when BCs are negative, allowing for appropriate antibiotic treatment of osteomyelitis in the era of CA-MRSA infections.
E. O. Mason Jr., None
K. G. Hulten, None
S. L. Kaplan, Pfizer: Grant Investigator, Research grant
Cerexa: Grant Investigator, Research grant
J. G. Vallejo, None