Impact of antibiotic pretreatment on cultures in children with osteomyelitis and septic arthritis: a retrospective review

Background In the management of pediatric osteomyelitis or septic arthritis, delay in treatment may affect outcome, while receipt of antibiotics prior to culture may affect culture results. We aimed to determine if pathogen identification decreased in cultures that were pretreated with antibiotics. Methods We conducted a retrospective cohort study of 584 hospitalized children between 30 days and 18 years of age admitted to two tertiary children’s hospitals. Logistic regression assessed the effect of antibiotic duration on blood, bone, joint aspirate, and “other” culture positivity. Results Overall, 42% of blood cultures, 70% of bone cultures, 39% of joint cultures, and 70% of “other” cultures were positive. Compared with children who did not receive antibiotics prior to culture, there were no significant differences in odds of a positive culture in children whose cultures were pretreated with antibiotics for any of the culture types [OR (95% CI) 0.90 (0.56–1.44) for blood cultures, 0.77 (0.25–2.34) for bone cultures, 0.71 (0.39–1.28) for joint cultures, 1.18 (0.58–2.41) “for other” cultures; all p > 0.05]. Furthermore, the duration (hours) of antibiotics in the pretreated cultures was also not a significant predictor of culture positivity (OR ranged from 0.99–1.00 for all cultures, p > 0.05). Conclusions Culture positivity was not associated with antibiotic pretreatment in any of the samples, even for longer duration of antibiotics prior to culture, though the small sample size of subgroups is an important limitation. In pediatric patients hospitalized with osteomyelitis and/or septic arthritis, early initiation of antibiotics may not affect culture positivity.

Specific Magnetic Resonance Imaging Findings as Predictors of Osteomyelitis in Routine Clinical Practice

Background: The gold standard for the diagnosis of osteomyelitis is histopathology combined with positive bone cultures. Magnetic Resonance Imaging (MRI) is often used to aide diagnosis and guide treatment decisions. The purpose of the study was to examine the association of MRI findings with, and their sensitivity and specificity in identifying osteomyelitis as proven by bone histopathology and bone culture in routine clinical practice. Materials and Methods: A retrospective analysis of patients with bone specimens obtained by biopsy or at resection for suspected osteomyelitis during 2010-2014 at an academic medical center in New York City. We used bivariate analysis to compare findings of patients who did or did not have osteomyelitis confirmed on histopathology (Analysis 1) and those who had either bone histopathology demonstrating osteomyelitis, positive bone cultures or both or who had neither (Analysis 2). Results: We identified 103 patients with an MRI in the week prior to bone biopsy or bone resection. In Analysis 1, 52 (50.5%) of 103 patients had osteomyelitis confirmed on histopathology. In Analysis 2, 72 (70%) patients had proven osteomyelitis. These groups with and without osteomyelitis did not differ significantly with respect to the frequency of marrow edema, cortical erosions, decreased T1 signal or increased T2 signal in either analysis and the sensitivity and specificity of MRI findings for detecting osteomyelitis was lower than reported in prior studies. Conclusions: Based on the above results, clinicians should be aware that the sensitivity and specificity of MRI findings for histologic and microbiologic osteomyelitis may be less in real world practice than is reported in formal studies.

Utility of Diagnostic Bone Biopsies in the Management of Osteomyelitis Through Retrospective Analysis: How Golden Is This Gold Standard?

Background Bone biopsy is considered the gold standard for diagnosis and treatment of osteomyelitis (OM), but few studies have investigated the extent to which it influences antimicrobial therapy in non-vertebral bones. The purpose of this study was to evaluate clinician-initiated changes to empiric antimicrobial therapy after obtaining bone biopsy results. A secondary aim was to identify predictors of a positive bone culture. Methods We retrospectively reviewed all cases of non-vertebral OM in patients who underwent image-guided bone biopsies between 2009 and 2016. Data on pathologic and microbiologic yield were collected and logistic regression was used to determine potential factors affecting the microbiologic yield. Post-biopsy empiric antibiotics and final antibiotics were compared with determine if there was a change in antibiotic treatment after biopsy results were reported. Results We evaluated 203 bone biopsies in 185 patients. Samples from 115 (57%) cases were sent to pathology, of which 33 (29%) confirmed OM. All samples were sent to microbiology and 57 (28%) yielded a positive result. Diabetes (OR=2.39, P = 0.021) and white blood cell count (OR=1.13, P = 0.006) were significantly associated with positive bone cultures in multivariate analyses. There was no association between positive cultures and number of samples cultured, needle size, prior antibiotic use, or antibiotic-free days. Post-biopsy empiric antibiotics were given in 138 (68%) cases. Therapy was narrowed to target specific organisms in seven cases and changed due to inadequate empiric treatment in three cases. Targeted therapy was initiated in 4/65 cases, in which empiric antibiotics had been initially withheld. While final antibiotics were withheld in 38/146 with negative bone cultures, empiric antibiotics were discontinued in only eight cases. Conclusion In patients with non-vertebral OM, bone biopsy cultures rarely yielded results that necessitated changes in antibiotic management. Identified bone organisms were treated by empiric therapy in most patients. While bone biopsy remains the gold standard diagnostic test for OM, further work is needed to identify patients whose management may be impacted by this procedure. Disclosures All authors: No reported disclosures.

Image-based modeling: A novel tool for realistic simulations of artificial bone cultures

Computational modeling has been promulgated as a means of optimizing artificial bone tissue culturing ex vivo. In the present report, we show, as a proof-of-concept, that it is possible to model the exact microenvironment within the scaffolds while accounting for their architectural complexities and the presence of cells/tissues in their pores. Our results clearly indicate that image-based modeling has the potential to be a powerful tool for computer-assisted tissue engineering.

Corynebacterium Striatum: A Concerning Pathogen of Osteomyelitis in the Diabetic Patient

INTRODUCTION AND OBJECTIVES: Corynebacterium striatum (C. striatum) is known to colonize the skin and mucous membranes of most normal human hosts. While it is frequently isolated in clinical laboratories, the clinical significance of C. striatum is often unknown with respect to diabetic foot infections with osteomyelitis. There have been very few studies published on this topic, and even fewer that report on treatment courses. To our knowledge, there has been no study published reporting diabetic foot osteomyelitis with isolation of C. striatum from bone culture. METHODS: Four patients were known to have been treated at our facility for C. striatum diabetic foot osteomyelitis. The medical records for each patient were thoroughly reviewed with close attention directed towards the past medical history, wound duration, wound and bone cultures, antimicrobial therapy and clinical outcomes. RESULTS: Bone cultures of all 4 patients were notable for C. striatum. Diphtheroids were also noted on wound cultures for 3 patients which were not speciated. All bone cultures were obtained during surgical treatment of the diabetic foot infection. All patients were type II diabetics but varied with respect to age and gender. All patients were treated with an extended course of antibiotics and/or surgical resection of osteomyelitis. Patients were followed until complete wound closure. CONCLUSIONS: We report four cases of diabetic foot osteomyelitis in which C. striatum was noted and treated as a pathogen. Diphtheroids are often overlooked as a potential pathogen in diabetic foot infections and rarely treated as such. However, our findings suggest that clinicians should consider C. striatum as a possible cause of osteomyelitis, especially when patients fail to completely heal wounds in a timely manner that have previously and repeatedly displayed Diphtheroids from cultures.