Title : Antimicrobial susceptibility of Kingella kingae isolates from Australia and New Zealand: Implications for empirical treatment of paediatric osteoarticular infections
Abstract:
Kingella kingae is increasingly recognised as a leading cause of osteoarticular infections (OAI) in young children. Although generally susceptible to a broad spectrum of antibiotics, regional susceptibility data remain scarce, particularly in Australasia. In this study, we characterised the antimicrobial profiles of 61 K. kingae isolates collected across Australia and New Zealand to inform empirical treatment recommendations, with a focus on first-generation cephalosporins.
Susceptibility testing was performed using broth microdilution, disk diffusion, or both, in accordance with ISO 20776-1:2019 and EUCAST guidelines. All isolates were beta-lactamase negative and showed high susceptibility to penicillin, ampicillin, amoxicillin, and second- and third-generation cephalosporins. Notably, first-generation cephalosporins—particularly cefalexin and cefazolin—demonstrated potent in vitro activity (MIC?? ≤ 2 mg/L). In contrast, flucloxacillin and cloxacillin displayed higher MIC?? values (16 mg/L and 4 mg/L, respectively), indicating limited activity. All isolates were fully susceptible to azithromycin and erythromycin. Interestingly, clavulanic acid markedly lowered amoxicillin MICs, even in the absence of beta-lactamase production, suggesting an intrinsic target interaction.
These findings represent the first regional susceptibility data for K. kingae in Australasia and support the empirical use of first-generation cephalosporins in paediatric OAI. They also underscore the need for EUCAST interpretive criteria specific to K. kingae, particularly for commonly used oral beta-lactams. Further studies across diverse geographic settings are warranted to guide clinical practice and support the development of targeted breakpoints.
