• Kingella belongs to the family Neisseriaceae in the γ-subgroup of the
• Species:
  • K. denitrificans
  • K.oralis
  • K. potus.
  • K. kingae was formerly a member of the genus Moraxella.
• K. denitrificans was formerly called CDC group “TM-1.”
• Kingella oralis was recovered from human dental plaque of a patient with adult periodontitis.
• Kingella potus was isolated from the zookeeper’s wound. Three days earlier, he had sustained the bite of a kinkajou (Potus potus).

Clinical Significance of Kingella Species:

• K. kingae is being recognized as an important human pathogen though it’s part of the normal microbiota of the upper respiratory and genitourinary tracts.
• In pediatric patients, it has emerged as a significant pathogen.
• It has caused primarily bacteremia and skeletal infections in them.
• In infants after 6 months of age, K. kingae colonizes the upper respiratory tract.
• In between 6 months and 2 years of age, the rate of colonization increases 10% to 12%
• Then the colonization begins to decline after this time.
• In a study it was found, during the first 2 years of life, invasive K. kingae disease occurred most frequently in previously healthy children.
• Transmission can occur from child to child by the respiratory route.
• Organisms may get entrance into the bloodstream through breaches in the oropharyngeal mucosa.
• In children, it causes the bone and joint infections.
• These infections present as bacteremia, septic arthritis, osteomyelitis, discitis, tenosynovitis, and dactylitis.
• Systemic infections in infants presents:
  • low-grade fevers
  • viral upper respiratory tract infections
  • frequently stomatitis are present
• In most cases, K. kingae septic arthritis is an acute infection.
• From these patients, blood cultures are usually negative.
• K. kingae septic arthritis is usually monoarthritic.
• It involves joints being the knee, hip, and ankle.
• K. kingae also causes osteomyelitis affecting the femur, other long bones, the tibia, ulna, radius, and calcaneus bones.
• K. kinage also causes spondylitis and intervertebral discitis.
• It also causes pediatric osteoarticular infections of the lower sternum and the junction between the manubrium and the xyphoid process.
• Invasive K. kingae causes the following infection in children:
  • acute lymphocytic leukemia
  • congenital heart disease.
• Rarely, bacteremia and endocarditis are caused by K. kingae.
• In the patients with heart disease such as rheumatic heart disease, cardiac malformations, or those with cardiac prostheses, K. kingae endocarditis occurs.
• In adults and school-age children, K. kingae endocarditis occurs.
• Complications of kingae endocarditis:
  • Pericarditis
  • paravalvular abscess
  • pericardial abscess
  • embolic phenomena
  • mycotic aneurysms
  • cerebral and pulmonary infarcts
  • septic shock
  • congestive heart failure.
• In women with systemic lupus erythematosis, K. kingae endocarditis with meningitis has been reported.
• In the immunocompetent adults, K. kingae bacteremia without endocarditis has been reported.
• It causes dental manipulations.
• Additional complications of bacteremia and bone infections include:
  • Meningitis
  • hematogenous orbital cellulitis
  • Endophthalmitis
  • soft tissue infection
  • corneal abscess.
• The clinical presentation of K. kingae bacteremia may mimic systemic neisserial infections (i.e., meningococcemia or disseminated gonococcal infection).
• K. denitrificans has also been reported as a cause of septicemia and native/prosthetic valve endocarditis.
• K. denitrificans has also been isolated from:
  • empyema fluid of a patient with bronchogenic carcinoma
  • the bone marrow of a patient with AIDS
  • the amniotic fluid of a patient with chorioamnionitis
  • a corneal ulcer

Cultural Characteristics of Kingella species:

• Kingella species are Gram-negative bacilli or coccobacilli.
• They occur in pairs or short chains.
• They are oxidase-positive and catalase-negative.
• All species grow on chocolate and blood agar
• Do not grow on MacConkey agar or other enteric media.
• All Kingella are negative for:
  • arginine dihydrolase
  • lysine and ornithine decarboxylases
  • urease
  • esculin hydrolysis
  • ONPG hydrolysis

Biochemical characteristics for the identification of Kingella species are:

• NA means not available
• HEM SBA: Hemolysis on sheep blood agar
• NO₃RED: reduction of nitrate to nitrite
• NO₂RED: reduction of nitrite to nitrogen gas
• ODC: ornithine decarboxylase
• ONPG: o-nitrophenyl-β-D-galactopyranoside
• DNase: Deoxyribonuclease

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