Aim. Kingella kingae seems to be the most common cause of osteoarticular infections (OAI) in children under 48 months of age (1). Recent studies had shown that K. kingae is poorly susceptible to anti-staphylococcal penicillin and some isolates produce beta-lactamase (2). This led to the need for new treatment guidelines for OAI in populations in which K. kingae is frequent. Our study aimed to design a model which could predict K. kingae OAI in order to initiate appropriate empirical treatment on hospital admission. Method. We performed a retrospective cohort study in children from 1 month to 15 years old diagnosed with OAI, hospitalized between 2006 and 2018. Mann-Whitney test and Fisher's exact test were used for data analysis. The model predicting K. kingae OAI was designed using logistic regression. Results. 247 children were included in the study, 126 (51%) had osteomyelitis (OM), 83 (33.6%) septic arthritis (SA) and 38 (15.4%) combined OM and SA. The median age was 52 (IQR 20–122) months, male-to-female ratio was 1.57:1. Pathogens were isolated in 101 (40.9%) cases with the following frequency: Staphylococcus aureus (n=59), K. kingae (n=13), Streptococcus pyogenes (n=11), Streptococcus pneumoniae (n=8). Patients with K. kingae OAI had lower CRP levels compared to other pathogens (p<0.05). WBC was higher compared to S. aureus OAI (p=0.011), children with K. kingae OAI were younger than children infected with S. aureus (p<0.001) and S. pyogenes (p=0.003). Based on this information we designed a predictive model using previous parameters as predictors of outcomes. The model had a 92.3% sensitivity and a 77.5% specificity. Then, we tried to test the model's predictive power based on the treatment failure of empirical anti-staphylococcal antibiotics in the group of children with OAI without the known pathogen. In the subgroup for which the model predicted K. kingae OAI, antibiotic treatment had to be changed in 6/59 cases. It had to be changed in only 1/83 cases in the non-K. kingae group (p=0.021). Conclusions. Despite poor specificity of the model, we found it to be more important to include all K. kingae OAI, that can be then properly treated. Additionally, with good specificity we acquire good negative predictive value, which means that children, for whom the model did not predict K. kingae OAI, can be safely treated with anti-staphylococcal penicillin

Osteoarticular infections (OAI) are a common cause of morbidity in children, and as opposed to adults is usually caused by haematogenous spread. The bacteriology of OAI in children is not well described in the South African context, therefore this study was designed to determine the bacteriology of OAI in our population. All patients that underwent surgery for the treatment of OAI over a 3-year period were identified and those with positive cultures where organisms were identified from tissue, pus, fluid or blood were included. Duplicate cultures from the same patient were excluded if the organism and antibiotic susceptibility profile was the same. Patients were categorised according to age and class of infection (Septic arthritis, acute osteomyelitis, fracture related infection, post-operative sepsis and chronic osteomyelitis) and organisms were stratified according to these categories. We identified 132 organisms from 123 samples collected from 86 patients. Most cultured organisms were from children older than 3-years with acute haematogenous septic arthritis, osteomyelitis, or both. Methicillin sensitive Staphylococcus aureus accounted for 56% (74/132) of organisms cultured. There were no cases of MRSA. The Enterobacterales accounted for 17% (22/132) of organisms cultured, mostly in the fracture related and post-operative infection groups. Of these, 6 each were extended spectrum B-lactamase producers and AmpC producers. There were no carbapenemase producing Enterobacterales. Kingella kingae was not isolated in any patient. Methicillin sensitive S. aureus is the most common infecting organism in paediatric OAI and an anti-staphylococcal penicillin such as cloxacillin or flucloxacillin is the most appropriate empiric treatment for haematogenous OAI in our environment. In fracture related or post-operative infections, Enterobacterales were more frequently cultured, and treatment should be guided by culture and susceptibility results

Aim. While 16S rRNA PCR - Sanger sequencing has paved the way for the diagnosis of culture-negative bacterial infections, it does not provide the composition of polymicrobial infections. We aimed to evaluate the performance of the Nanopore-based 16S rRNA metagenomic approach using partial-length amplification of the gene, and to explore its feasibility and suitability as a routine diagnostic tool for bone and joint infections (BJI) in a clinical laboratory. Method. Sixty-two clinical samples from patients with BJI were sequenced on MinION* using the in-house partial amplification of the 16S rRNA gene. BJI were defined based on the ICM Philly 2018 and EBJIS 2021 criteria. Among the 62 samples, 16 (26%) were culture-positive, including 6 polymicrobial infections, and 46 (74%) were culture-negative from mono- and polymicrobial infections based on Sanger-sequencing. Contamination, background noise definition, bacterial identification, and time-effectiveness issues were addressed. Results. Results were obtained within one day. Setting a threshold at 1% of total reads overcame the background noise issue and eased interpretation of clinical samples. The partial 16S rRNA metagenomics approach had a greater sensitivity compared both to the culture method and the Sanger sequencing. All the 16 culture-positive samples were confirmed with the metagenomic sequencing. Bacterial DNA was detected in 32 culture-negative samples (70%), with pathogens consistent with BJI. The 14 Nanopore negative samples included 7 negative results confirmed after implementation of other molecular techniques and 7 false-negative MinION results: 3 Kingella kingae infections detected after targeted-PCR only, 2 Staphylococcus aureus infections and 2 Pseudomonas aeruginosa infections sterile on agar plate media and detected only after implementation of blood culture media, advocating for the very low inoculum. Conclusions. The results discriminated polymicrobial samples, and gave accurate bacterial identifications compared to Sanger-based results. They confirmed that Nanopore technology is user-friendly as well as cost- and time-effective. They also indicated that 16S rRNA targeted metagenomics is a suitable approach to be implemented for routine diagnosis of culture-negative samples in clinical laboratories. * Oxford Nanopore Technologies

Osteomyelitis and septic arthritis are common pathologies in young children. Because of their skeletal immaturity, children are particularly vulnerable to orthopaedic complications, including limb-length discrepancies, angular deformities, chondrolysis, etc. The primary objective of this study was to review the clinical follow up and outcomes of paediatric patients diagnosed with osteoarticular infections. The secondary purpose was to look for significant differences in the clinical characteristics between the one with and without complications. Patients' medical charts, hospitalised between 2010 and 2016, were retrospectively reviewed. The inclusion criteria were: patients (1) aged of less than 10 years old (2) treated and followed for osteomyelitis of long bones of upper and lower extremities and/or septic arthritis (3) with at least one year of radiological follow up. The exclusion criterion was: (1) any concomitant chronic diseases. The information collected included demographic and clinical data. A late sequela was defined as a limb-length discrepancy superior to 5 mm or an abnormal articular angulation of more than 5°, or a symptomatic chondropathy. Patients were separated in two groups: with and without complications. Chi-square tests were used for categorical variables and Mann-Whitney U tests for continuous data in order to establish significant differences between both groups. Of the 401 patients with osteomyelitis and/or septic arthritis treated in our tertiary paediatric hospital over 7 years, 50 met the inclusion criteria. There were 24 girls and 26 boys. The etiological agent was identified in 56% of the cases. Staphylococcus aureus was the predominant causal pathogen (50%), followed by Kingella kingae (19.2%). The mean follow up was 780 days. Six out of 50 (12%) patients had physeal or chondrolytic complications at the latest follow-up. The only significant difference between the 2 groups was the delay between onset of symptoms and initiation of antibiotic therapy (P = 0.039). Only 12.5% of the patients were followed up at least one year. In the population of 50 skeletally immature patients without comorbidities, 12% had a sequela. The delay in initiating antibiotic treatment was significantly longer in the group with the presence of sequelae. The results of this study reveal that there were low rates of outpatient follow-up reaching more than a year after an osteoarticular infection, thus raising the question about the importance of a follow up after such a diagnosis. Twelve percent of the patients had a growth or chondrolysis complication and this might be related to the delay before initiating antibiotic treatment

Aims. Microbiological diagnosis of bone and joint infections (BJIs) is pivotal. However, no consensus exists about the best choice for techniques to be used and the best indications for molecular methods. Our objectives were: (i) to compare the performance of various microbiological diagnostic methods (cultural and molecular) on synovial fluid specimens and (ii) to select an algorithm for optimizing the diagnosis of BJIs in adults. Methods. This prospective multicentric study (in Lyon and Saint-Etienne, France) included 423 joint fluid samples, collected from 333 adult patients (median age 69 years) suspected for BJI on the basis of medical history and clinical symptoms. For each inclusion, joint fluid and blood culture were collected concomitantly. The synovial fluid was also inoculated into blood culture bottles. Cytology, culture (using 5 solid media and an enrichment broth, incubated for 15 days), universal 16S rRNA PCR and PCR targeting Staphylococcus spp, S.aureus, Streptococcus spp, S.pneumoniae, Kingella kingae, Borrelia burgdorferi and Propionibacterium acnes were systematically performed on synovial fluid. Results. Prosthetic materials were present in 65.0% of the cases and 31.7% of the patients had received antibiotics in the 15 days before puncture. Out of 423 joint fluids, 265 (62.6%) were positive by at least one diagnostic technique (cultural or molecular): 219 mono- and 46 poly-microbial, for a total of 322 bacteria. Identified bacteria were staphylococci in 54.0%, streptococci-enterococci in 15.2%, Gram-negative bacilli in 14.0%, anaerobic species in 10.9% and other bacteria in 5.9% of cases. Comparing the individual performance of each cultural technique, blood culture bottles showed the highest rate of positivity (detecting 61.4 and 58.4% of the bacteria, for the paediatric and anaerobic bottles, respectively) but cannot be performed alone and require to be combined with solid media. The 16S rDNA PCR was positive in only 49.2% of the cases whereas higher detection was obtained with specific PCR. Blood cultures performed concomitantly with joint puncture were positive in only 9.7% of the cases. Conclusions. In order to simplify the culture procedures and to precise the place of PCR for synovial fluid, we propose the following algorithm: joint fluids should be inoculated onto 3 solid media (blood and chocolate agars for 2 days, anaerobic blood agar for 10 days), associated with inoculation into blood culture bottles for 10 days. If culture remains negative, 16S rDNA PCR and/or Staphylococcus PCR should be added. Applying this algorithm on our cohort, 93.6% of the bacteria would have been detected

Osteoarticular infections (OAI) in children provide both diagnostic and therapeutic challenges. Recent data suggest that management of OAI can be simplified with shorter treatment duration and earlier switch to oral antibiotics. The aim of the study was to evaluate management and outcome of OAI in children at our center. A retrospective review of all cases of osteoarticular infections (OAI) in children <15 years of age treated at our institution, from May, 2006 to April, 2015 was performed. Treatment duration and outcome in two periods, 2006–2011 and 2012–2015 were compared. In a 9-year period there were 164 cases (93 cases in 2006–2011 and 71 cases in 2012–2015) of OAI with 12–24 cases annualy. A male preponderance among patients was observed with a male-to-female ratio of 1,88:1. There were 86 osteomyelitis (OM) cases, 52 septic arthritis (SA) cases and 26 OM and SA cases. The majority of cases involved lower limbs. One-third of children with OAI were either active in sport and/or had a recent history of mild trauma. In 13 (8%) cases OAI developed after varicella. There were 74 microbiologically confirmed infections and the main causative agent was Staphylococcus aureus (47 cases), followed by Streptococcus pyogenes (8 cases), S. pneumoniae (5), Kingella kingae and Salmonella (3 cases, respectively). Surgical treatment was required in 46 cases, further 18 required one or multiple joint aspirations. One child with S. aureus bacteremia had endocarditis. In one child with sepsis and multiorgan failure necrosis of the femur developed and in two bone abscesses were drained 3 and 12 months after acute episode. All 3 children had Panton-Valentine leukocidin (PVL)-positive S. aureus infection. All other children recovered without permanent sequelae. When comparing treatment duration, average treatment was shorter in 2012–2015 (31,3 days) than in 2006–2011 (38,1 days, p=0,0003), particularly due to shortening of parenteral treatment (9,0 days vs. 16,1 days, p<0,0005). The outcome was similar in both periods. OAI often occur in children who engage in sports or have a history of recent trauma. The majority of infections are caused by S. aureus, which can be severe and/or complicated if the isolate is PVL-positive. Antimicrobial treatment can be shortened and early switch to oral treatment seems to be safe. In general, prognosis of OAI in children is excellent