Kingella kingae

Kingella kingae is a species of Gram-negative bacteria that is part of the normal flora of the human oropharynx. It is a member of the HACEK group of bacteria, which are a known cause of endocarditis in young children and adults with underlying heart conditions. Kingella kingae is increasingly recognized as an important pathogen in pediatric populations, responsible for a variety of invasive infections including osteomyelitis (infection of the bone), septic arthritis (infection in joints), and bacteremia (presence of bacteria in the blood).

Characteristics

Kingella kingae is a fastidious, Gram-negative coccobacillus that requires enriched media for growth, such as blood agar, and grows best in an atmosphere supplemented with 5% CO2. It is oxidase and catalase positive, and can be differentiated from other members of the Neisseriaceae family by its ability to produce acid from carbohydrates.

Epidemiology

The bacterium is most commonly found in children under the age of 4, where it colonizes the oropharynx. Transmission is thought to occur through close personal contact or respiratory droplets. While Kingella kingae is part of the normal flora in some individuals, it can invade the bloodstream and cause disease in those with certain risk factors or underlying conditions.

Clinical Manifestations

Kingella kingae can cause a range of clinical syndromes, the most common being osteomyelitis and septic arthritis. These infections often present with subtle symptoms, making early diagnosis challenging. Other less common infections caused by Kingella kingae include endocarditis, which can lead to significant morbidity and mortality if not promptly treated, and bacteremia without a focal source.

Diagnosis

The diagnosis of Kingella kingae infections can be difficult due to its fastidious nature. Polymerase chain reaction (PCR) assays have become a valuable tool for detecting K. kingae DNA directly from clinical specimens, offering a more sensitive and specific method than traditional culture techniques. Blood cultures, while useful, may not always be positive, especially in cases of localized infections such as osteomyelitis or septic arthritis.

Treatment

The treatment of infections caused by Kingella kingae typically involves antibiotics. Beta-lactam antibiotics, such as ampicillin or a cephalosporin, are commonly used due to their effectiveness against K. kingae. In cases of osteomyelitis or septic arthritis, prolonged antibiotic therapy is often required, and surgical intervention may be necessary to drain abscesses or debride infected tissue.

Prevention

Currently, there are no vaccines available to prevent Kingella kingae infections. Good hand hygiene and avoiding close contact with individuals who have symptomatic infections may help reduce the risk of transmission.

Conclusion

Kingella kingae is an emerging pediatric pathogen that can cause a variety of invasive infections. Awareness among healthcare providers of its potential for causing disease, along with advances in diagnostic techniques, can help in the early detection and treatment of infections caused by this organism.