Kingella kingae Osteoarticular Infections Approached through the Prism of the Pediatric Orthopedist

Nowadays, Kingella kingae (K. kingae) is considered as the main bacterial cause of osteoarticular infections (OAI) in children aged less than 48 months. Next to classical acute hematogenous osteomyelitis and septic arthritis, invasive K. kingae infections can also give rise to atypical osteoarticular infections, such as cellulitis, pyomyositis, bursitis, or tendon sheath infections. Clinically, K. kingae OAI are usually characterized by a mild clinical presentation and by a modest biologic inflammatory response to infection. Most of the time, children with skeletal system infections due to K. kingae would not require invasive surgical procedures, except maybe for excluding pyogenic germs’ implication. In addition, K. kingae’s OAI respond well even to short antibiotics treatments, and, therefore, the management of these infections requires only short hospitalization, and most of the patients can then be treated safely as outpatients.

Utility of Methicillin-Resistant Staphylococcus aureus Nares Screening in Hospitalized Children with Acute Infectious Disease Syndromes

Studies in adults support the use of a negative methicillin-resistant Staphylococcus aureus (MRSA) nares screening (MNS) to help limit empiric anti-MRSA antibiotic therapy. We aimed to evaluate the use of MNS for anti-MRSA antibiotic de-escalation in hospitalized children (<18 years). Records of patients admitted between 1 January 2015 and 31 December 2020 with a presumed infectious diagnosis who were started on anti-MRSA antibiotics, had a PCR-based MNS, and a clinical culture performed were retrospectively reviewed. A total of 95 children were included with a median age (range) of 2 (0–17) years. The top three diagnosis groups were skin and soft tissue infections (n = 38, 40%), toxin-mediated syndromes (n = 17, 17.9%), and osteoarticular infections (n = 14, 14.7%). Nasal MRSA colonization and growth of MRSA in clinical cultures was found in seven patients (7.4%) each. The specificity and the negative predictive value (NPV) of the MNS to predict a clinical MRSA infection were both 95.5%. About half (n = 55, 57.9%) had anti-MRSA antibiotics discontinued in-house. A quarter (n = 14, 25.5%) were de-escalated based on the negative MNS test alone, and another third (n = 21, 38.2%) after negative MNS test and negative culture results became available. A high NPV suggests that MNS may be useful for limiting unnecessary anti-MRSA therapy and thereby a useful antimicrobial stewardship tool for hospitalized children. Prospective studies are needed to further characterize the utility of MNS for specific infectious diagnoses.

244. Risk Factors Associated with Complications/Sequelae in Pediatric Patients with Osteomyelitis

Background Osteoarticular infections are serious invasive pathologies in the pediatric population. They have high morbidity, especially if antimicrobial treatment is inadequate and late. Based on pediatric series patients with osteomyelitis require prolonged antibiotic schemes, long stay and high hospital costs, multiple surgical procedures and develop short and long-term sequelae. Methods A retrospective, observational, longitudinal and analytical study was conducted in patients under 17 years of age diagnosed with osteomyelitis at the National Institute of Pediatrics from January 2009 to January 2019. Demographic information, clinical presentation, microbiological, treatment and six-month follow-up were recorded. Results A total of 109 patients were included, 57 (52%) males with median age of 98 (1-205) months with predominance in previous healthy (66%). By temporality, the chronic form predominated in 72%. The history of trauma was identified in 26% and fracture 19%. The most affected bone was femur 26%. Blood culture was performed in 55%, secretion culture in 52.2% with isolation in 56%. Methicillin-susceptible Staphylococcus aureus (MSSA) was the main agent identified. Complications occurred in 37%, the most frequent was surgical wound infection in 13% followed by fracture 11%. Risk factors for complications were chronic osteomyelitis RR 5.7 (CI 1.8-17.9), Sepsis/Shock RR 3.8 (CI 1.08-13-8) and MSSA infections RR 2.7 (CI 1.01-7.5); Risk factors for surgical site infection included initial fracture RR 3.5 (CI 1-11), local ulcer RR 4.2 (CI 1.3-13.06) and MSSA infection RR 5.9 (CI 1.8-19.4). Risk factors for limitation to movement included chronic osteomyelitis RR 4.87 (CI 1.6-14), fever RR 2.5 (CI 1.15-5.5), Sepsis/shock RR 5.3 (CI 1.3-20) (p 0.013) and MSSA infection RR 4.1 (CI 1.4-11.9). Conclusion Osteomyelitis is still a health problem in our country. The diagnosis of osteomyelitis may be challenging as lack of suspicion often leads to delayed diagnosis. Knowledge of the risk factors for complications in pediatric patients could be useful to give early and proper antibiotic and surgical treatment. It is a priority to have a multidisciplinary team for the diagnosis and treatment of osteoarticular infections. Disclosures All Authors: No reported disclosures

182. Back to The Future: Increasing Penicillin Susceptibility among Methicillin-Susceptible Staphylococcus aureus Osteoarticular Infections in Children

Background Starting in the late 1940s-1950s Staphylococcus aureus isolates gained resistance to penicillin largely through the acquisition of β-lactamases. In recent years, some centers have described an increase in the proportion of methicillin susceptible S. aureus (MSSA) which are also susceptible to penicillin (PSSA). There are little data on the prevalence or clinical significance of PSSA in children. Acute hematogenous osteoarticular infections (AHOAIs, including osteomyelitis and septic arthritis) are the most common manifestation of invasive S. aureus disease in children. We investigated the prevalence of penicillin susceptibility among MSSA AHOAI isolates at two children’s hospitals. Methods MSSA AHOAI isolates were obtained through surveillance studies at Texas Children’s (TCH) and St. Louis Children’s Hospitals (SLCH) from 1/2011- 12/2019. All isolates underwent PCR for blaZ β-lactamase, PVL genes and agr group. All blaZ negative isolates then underwent penicillin susceptibility testing using macrobroth dilution. Isolates which were blaZ negative and had a penicillin MIC ≤ 0.125 μg/ml were regarded as PSSA. Results 329 unique isolates were available and included in the study. The median patient age was 9.2 years (IQR: 5.1-12.2). Overall, 22 isolates were found to be penicillin susceptible (6.7%). No PSSA isolates were detected prior to 2015 but increased yearly thereafter; by the final study year 20.4% of isolates were PSSA (p=0.001, Figure 1). Patients with PSSA isolates were slightly older than those with resistant isolates (median age 11.8 years vs. 9.1 years, p=0.08) and PSSA were more commonly identified at SLCH (12.9% vs. 5.2%, p=0.04). PSSA were similar to penicillin-resistant isolates in terms agr group and PVL carriage as well as clinical presentation and outcomes. For PSSA, the MIC90 for penicillin (0.06 μg/ml) was much lower than that for other β-lactams (Figure 2). The figure describes the relative frequency of penicillin susceptible S. aureus (PSSA) over time among MSSA osteoarticular infection isolates in children. Distribution of MICs to penicillin, ampicillin, cefazolin, cephalexin and oxacillin among PSSA isolates. Conclusion PSSA appears to be increasing among AHOAI isolates in US children, although geographic variability does occur. Overall, PSSA isolates are associated with a similar clinical presentation as penicillin-resistant isolates. Penicillin susceptibility testing may serve as an avenue for future stewardship intervention in staphylococcal infections. Disclosures 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) Kristina G. Hulten, PhD, Pfizer (Research Grant or Support) Sheldon L. Kaplan, MD, Pfizer (Research Grant or Support)