Background: Kingella kingae is a gram-negative coccobacillus, increasingly recognized as an invasive pediatric pathogen. To date, only few small series of invasive K. kingae infections have been published, mostly from single medical centers. A nationwide multicenter study was performed to investigate the epidemiologic, clinical, and laboratory features of children with culture-proven K. kingae infections.
Methods: Clinical microbiology laboratories serving all 22 medical centers in Israel were contacted in a search for children aged 0 to 18 years from whom K. kingae was isolated from a normally sterile site, dating from as far back as possible until December 31, 2007. Medical records of identified patients were reviewed using uniform case definitions.
Results: A total of 322 episodes of infection were identified in 321 children, of which 96% occurred before the age of 36 months. The annual incidence in children aged <4 years was 9.4 per 100,000. Infections showed a seasonal nadir between February and April. Skeletal system infections occurred in 169 (52.6%) children and included septic arthritis, osteomyelitis, and tenosynovitis. Occult bacteremia occurred in 140 children (43.6%), endocarditis in 8 (2.5%), and pneumonia in 4 (1.2%). With the exception of endocarditis cases, patients usually appeared only mildly ill. About one-quarter of children had a body temperature <38°C, 57.1% had a blood white blood cell count <15,000/mm3, 22.0% had normal C-reactive protein values, and 31.8% had nonelevated erythrocyte sedimentation rate.
Conclusions: K. kingae infections usually occur in otherwise healthy children aged 6 to 36 months, mainly causing skeletal system infections and bacteremia, and occasionally endocarditis and pneumonia. Clinical presentation is usually mild, except for endocarditis, necessitating a high index of suspicion.