Kingella spp.

Bacteria:

Fastidious gram-negative coccobacilli that appear in pairs or short chains.
Commensal of the mouth and upper respiratory tract.
The genus Kingela have species like  – K. kingae, K. denitrificans, Kingella negevensis, K. oralis etc.

Identification:

It appears as pairs/short chains of plump bacilli (or coccobacilli) with tapered ends.
Capnophilic and facultatively anaerobic, nonmotile, non-spore-forming.
Beta-haemolytic colonies on blood agar often produce marked pitting of the agar surface.
It is catalase, urease, and indole tests negative. It is oxidase positive.

Kingella kingae produces 4 different types of colonies-

• A spreading-corroding type – a small central colony encircled by a wide fringe,
• A non-spreading/noncorroding type – a flat colony surrounded by a narrow fringe,
• A dome-shaped colony with no noticeable fringe
• Small-colony variants – pinpoint colonies on blood agar plates and no growth on Thayer-Martin medium

Identification could be made using – API NH, Vitek 2, MALDI-TOF, 16S rRNA gene sequencing. Remel RapID NH kit is not reliable.

Pathogenicity:

• Pilli – adherence and colonisation.
• Capsule – protection from phagocytosis and complement-mediated killing.
• Biofilm formation.
• RTX (repeat-in-toxin) toxin – broad-spectrum cytotoxicity, adherence to mucosa and persistence in the body.
• Outer Membrane Vesicles.

Predisposing factors/association:

Varicella infection, stomatitis, failure to thrive, congenital heart disease, prolonged corticosteroid therapy, primary immunodeficiency, haematological malignancies, liver cirrhosis, end-stage renal disease, sickle cell anaemia, diabetes mellitus, cardiac valve pathology, systemic lupus erythematosus, rheumatoid arthritis, renal transplants, solid tumours, or AIDS.

[Yagupsky 2015]

Clinical Condition:

• Kingella infection is mild unless associated with a deep infection – Fever, rhinorrhea, pharyngitis, stomatitis, diarrhoea, transient bacteraemia.
• Deep infections:
  Endocarditis – it is a part of the HACEK group of organisms. It could be associated with the embolic phenomenon.
  Septic arthritis and osteomyelitis – the commonest cause of septic arthritis in 6m to 3 years olds, usually involves large weight-bearing joints: association – varicella, stomatitis.
  Spondylodiscitis.
  Lower respiratory tract pleural empyema.
  Pediatric vaginitis.
  Chorioamnionitis, and
  Granulomatous disease in AIDS patients

Treatment: 

• Penicillin or cephalosporin group of drugs are usually used for treatment – The drug of choice is usually a third-generation cephalosporin- cefotaxime or ceftriaxone.
• Other antibiotics to which Kingella is susceptible in vitro: aminoglycosides, trimethoprim-sulfamethoxazole, tetracycline, erythromycin, and fluoroquinolones.
• Duration of treatment: The deep infection needs 4-12 weeks of treatment, depending on the condition.

Questions:

Short answer question –
Kingella kingae,
Septic arthritis in children,
Kingella arthritis,
HACEK endocarditis.