This is a multi- centre trial of children with bone and joint infections (BJIs) at eight major paediatric hospitals in Australia and New Zealand. The primary objective is to establish if in children with acute, uncomplicated BJIs, entirely oral antibiotic treatment is not inferior to initial intravenous (IV) treatment for 1 to 7 days followed by an oral antibiotic course in achieving full recovery 3 months after presentation. Children will be randomly allocated to the 'entirely oral antibiotic' group or the 'standard treatment' group.

Children with acute onset BJIs who present to the participating sites will be enrolled into the trial if eligible (see eligibility criteria) and randomly allocated into two groups. Children in the 'standard treatment group' will receive standard treatment for BJIs, which consists of IV antibiotics for 1-7 days followed by 3 weeks of oral antibiotics. Children in the 'entirely oral treatment group' will receive high dose oral antibiotics, followed by the standard dose of oral antibiotics for 3 weeks. The outcomes of children in each of the two groups will be compared to determine whether BJIs can be treated without needing a course of IV antibiotics.

Inclusion Criteria:

• Children aged 1 to 18 years with acute, uncomplicated, community-acquired bone and joint infection who fulfil pre-defined clinical criteria.

Exclusion Criteria:

1. Infection due to bacteria resistant to cefalexin or atypical infection (e.g. mycobacterial, fungal)
2. Features of sepsis as defined by the presence of organ dysfunction (defined using definitions within the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score)
3. Concomitant severe, invasive infection e.g. necrosing fasciitis
4. Complicated infection (e.g. presence of prosthetic material; large subperiosteal (>3mm) or soft tissue abscess without surgical intervention; infection secondary to or complicated by trauma)
5. History of allergy to cephalosporin antibiotics or immediate, severe reaction to penicillins
6. Received more than three IV or oral dose of an antibiotic with activity against the likely bacteria causing the current infection
7. Prior episode of OM or SA
8. Prior condition predisposing to poor absorption (e.g. inflammatory bowel disease, current gastrointestinal symptoms) or complicated disease (e.g. immunodeficiency)
9. Prior enrolment in the trial
10. Current recipient of another investigational product as part of a clinical trial

The de-identified data set collected for this analysis of the BEST trial will be available six months after publication of the primary outcome.

The study protocol, analysis plan and consent forms will also be available. The data may be obtained from the Murdoch Children's Research Institute by emailing amanda.gwee@rch.org.au

Time Frame: 6 months after publication of primary outcome

Prior to releasing any data the following are required: a data access agreement must be signed between relevant parties, the BEST Trial Principle and Associate Investigators must see and approve the analysis plan describing how the data will be analysed, there must be an agreement around appropriate acknowledgement and any additional costs involved must be covered. Data will only be shared with a recognised research institution which has approved the proposed analysis plan.