Kingella

Kingella kingae PHIL12451

Kingella is a genus of Gram-negative bacteria belonging to the family Neisseriaceae. This genus was named after Elizabeth O. King, a bacteriologist who first described these types of bacteria. Kingella species are part of the normal flora of the human oropharynx (the part of the throat at the back of the mouth) and are primarily known for their role in invasive diseases in children and, less frequently, in adults. The most clinically significant species within this genus is Kingella kingae, which is recognized as an important cause of osteomyelitis (infection and inflammation of the bone) and septic arthritis (infection in a joint) in young children. Other species include Kingella denitrificans, Kingella oralis, and Kingella potus, which are less commonly associated with human disease.

Characteristics

Kingella species are oxidase-positive, catalase-negative, and can be differentiated from other members of the Neisseriaceae family by their ability to produce acid from carbohydrates in a unique manner. They are usually found as part of the normal flora in the upper respiratory tract but can become pathogenic under certain conditions. These bacteria are slow-growing, requiring enriched media and specific atmospheric conditions for laboratory culture, which can complicate diagnosis and treatment of infections they cause.

Pathogenesis

The pathogenicity of Kingella kingae is attributed to its ability to adhere to and invade human cells, evade the host immune response, and induce inflammation. It possesses a type IV pilus, a virulence factor that facilitates adherence to the epithelial cells of the oropharynx and invasion into the bloodstream. Once in the bloodstream, it can disseminate to various parts of the body, most notably the bones and joints, leading to osteomyelitis and septic arthritis. The exact mechanisms of Kingella's pathogenicity are still under investigation, with ongoing research focusing on its virulence factors and interaction with the host immune system.

Clinical Significance

Kingella kingae has emerged as a leading cause of osteoarticular infections in children under the age of 4 years. The typical presentation includes fever, bone pain, and reduced mobility of the affected limb. Diagnosis is challenging due to the fastidious nature of the organism and the often subtle and nonspecific clinical signs. Polymerase chain reaction (PCR) assays have improved the detection of Kingella kingae in clinical specimens, offering more rapid and sensitive diagnosis than traditional culture methods.

Treatment and Prevention

The treatment of infections caused by Kingella kingae involves the use of appropriate antibiotics, with a regimen often starting empirically and then tailored based on susceptibility testing. Prevention of Kingella kingae infections is challenging due to its presence as part of the normal oropharyngeal flora in children. However, awareness of the organism's role in pediatric infections and prompt diagnosis and treatment can significantly reduce morbidity associated with these infections.

Conclusion

Kingella species, particularly Kingella kingae, represent an important group of pathogens that can cause serious infections in children. Advances in diagnostic techniques, such as PCR, have improved the detection and understanding of these bacteria, leading to better management of the infections they cause. Ongoing research into the pathogenesis, virulence factors, and treatment strategies for Kingella infections is essential for further improving patient outcomes.