To assess the contemporary bacteriologic epidemiology of pediatric osteoarticular infection with particular regard to children's ages, because Kingella kingae has gained increasing recognition as the predominant pathogen for osteoarticular infection in young children.

Retrospective file review of enrolled children from 0 to 15 years of age, admitted to our institution from 2007 to 2015 for suspected osteoarticular infection (217 cases). Information on age, sex, the bone or joint infected, imaging studies, and laboratory data (including bacterial investigations) were collected for analysis.

Microorganism identification was possible for 138 infected children (63.6%), through blood (cultures or polymerase chain reaction [PCR]) and/or operative samples (cultures or PCR). Thirty-one patients (14.3%) were found to both have positive blood cultures and operative samples. The results of positive bacteriology specimens identified the most common causative pathogen for osteoarticular infection as K kingae (47.8% of microbiologically confirmed osteoarticular infections of all ages, and 87.7% in children between the ages of 6 and 48 months), significantly more common than Staphylococcus aureus (35.5% of microbiologically confirmed osteoarticular infections of all ages, and 78.2% in children >4 years of age).

Use of the appropriate PCR assays demonstrated that K kingae currently is the major bacterial cause of pediatric osteoarticular infection, especially in children <4 years of age in whom K kingae is more common than S aureus. PCR assays should be used in routine microbiologic laboratory evaluation to improve diagnostic performance. However, despite the use of molecular methods, there are many osteoarticular infections in which no microorganism is detected, which suggests that these infections may be caused by other as yet unrecognized fastidious microorganisms.