Kingella kingae Infections in Children

Abstract & Commentary

By Hal B. Jenson, MD, FAAP, Professor of Pediatrics, Tufts University School of Medicine; Chief Academic Officer, Baystate Medical Center, Springfield, MA, is Associate Editor for Infectious Disease Alert.

Dr. Jenson is on the speaker's bureau for Merck.

Synopsis: Kingella kingae is a cause of bacteremia and suppurative arthritis in otherwise healthy children less than 24 months of age, as well as bacteremia in persons of all ages with underlying medical conditions. Although of low virulence, K. kingae is an important pathogen to identify because of its propensity to cause endocarditis, and because of its resistance to vancomycin and clindamycin.

Source: Dubnov-Raz G, et al. Invasive Kingella kingae infections in children: clinical and laboratory characteristics. Pediatrics. 2008;122:1305-1309.

A retrospective study at a tertiary pediatric hospital in Israel of all children with a positive blood or synovial fluid culture for K. kingae during 1996-2006 revealed 62 children with invasive K. kingae infections. Of these, 42 (68%) had positive blood culture results and 20 (32%) had positive synovial fluid cultures. There were no cases of osteomyelitis documented. Among previously healthy children, all were older than five months, and only one was older than two years. Only eight (19%) children had pre-existing medical conditions, all of whom had bacteremia alone without arthritis. These eight children had a considerably broader age range at presentation, from 10 months to 15 years. Among all children, there were only mild-to-moderate elevations of serum levels of inflammatory markers including CRP (mean, 2.2 mg/dL; range: 0.4-17.0 mg/dL) and ESR (mean, 50.0 mm/hr; range, 14.0-115.0 mm/hr).

Children with arthritis presented, on average, after one day (range, 1-7 days) of symptoms, compared to three days (range, 1-7 days) for children with bacteremia alone. Concurrent illness (upper respiratory tract infections, acute gastroenteritis, or aphthous stomatitis) was identified in 16 (80%) children with arthritis. Only the large joints were involved, including the knee (7), ankle (7), hip (5), and shoulder (1). Joint symptoms resolved with a median of six days (range, 2-30 days), with a prolonged course of more than three weeks for two patients with very high initial CRP (11.9 and 17.0 mm/dL).

Of 16 patients who had cardiac echocardiography performed, four children were found to have endocarditis, including two children who were previously healthy. These four children had significantly higher levels of serum inflammatory markers, including CRP (7.6 mg/dL ± 4.9 mg/dL) and ESR (84.3 mm/hr ± 21.4 mm/hr), than children with bacteremia without endocarditis (p = 0.03 for each CRP and ESR). Two of these children required cardiac surgery because of native value destruction and rapid clinical deterioration.

The 39 antibiograms that were available showed that K. kingae isolates were susceptible to b-lactam antibiotics (except for one isolate that was resistant to methicillin), aminoglycosides (except for one isolate that was resistant to gentamicin and amikacin), tetracycline, minocycline, erythromycin, fluoroquinolones, and trimethoprim-sulfamethoxazole (except one isolate). All isolates were resistant to vancomycin and clindamycin.

Commentary

K. kingae is a slow-growing, gram-negative coccobacillus and a member of the HACEK (Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and K. kingae) group of fastidious organisms that are recognized as occasional causes of infective endocarditis. K. kingae is found in the nasopharynx of 45%-70% of children. Several reports of K. kingae suppurative arthritis and osteomyelitis in children have been reported in the past few years, including small clusters of cases in childcare facilities.

This report documents that K. kingae is an occasional cause of bacteremia and suppurative arthritis among previously healthy children less than two years of age, and also bacteremia in older children with underlying chronic disease. In this series, arthritis was often associated with mild, concurrent respiratory or intestinal tract illness. The inflammatory response in most cases is modest and does permit discriminating cases of K. kingae arthritis from bacteremia alone. A higher inflammatory response was characteristic of endocarditis, and for children with arthritis portended the need for longer treatment and a prolonged convalescence.

K. kingae is resistant to vancomycin and clindamycin, which are often used for empiric treatment of children with osteoarticular infections. K. kingae infection should be considered in otherwise healthy children less than three years of age with signs of bacteremia or osteoarticular infections. Children with suspected or proven K. kingae bacteremia or arthritis should be treated with regimens that include an effective b-lactam antibiotic. This is also important to reduce the risk of developing K. kingae endocarditis, which may result in serious, destructive native valve lesions.