Kingella: Growth on Blood Agar, Introduction, Pathogenecity, Laboratory

Kingella: Growth on Blood Agar, Introduction, Pathogenecity, Laboratory Diagnosis and Treatment

Kingella kingae on blood agar

Kingella kingae on blood agar is showing beta-hemolytic colonies after 48 hours incubation at 37°C as shown above image.

Introduction of Kingella

Scientific Classiofication

Domain: Bacteria
Phylum: Proteobacteria
Class: Betaproteobacteria
Order: Neisseriales
Family: Neisseriaceae
Genus: Kingella
Species: K. kingae

Kingella kingae is a species of Gram-negative that appears as pairs or chains of 4 to 8 plump (0.6 to 1 μm by 1 to 3 μm) coccobacilli, facultative anaerobic β-hemolytic bacterium showing non-motile, and non-spore-forming, exhibits negative catalase, urease, and indol tests, and, with rare exceptions, has oxidase activity and it is part of the bacterial flora of the throat in young children and is transmitted from child to child. When it causes disease, the clinical involvement is often subtle and preceded by a recent history of stomatitis or upper respiratory infection (URTI). First isolated by Elizabeth O. King in 1960 and it is the fifth member of the HACEK group of fastidious Gram-negative bacteria that cause endocarditis.

Predisposing Conditions to Cause Infection by Kinsella

Following are predisposing conditions-

congenital heart disease
prolonged corticosteroid therapy
primary immunodeficiency
hematological malignancies
liver cirrhosis
end-stage renal disease
Sickle cell anemia
diabetes mellitus
cardiac valve pathology
systemic lupus erythematosus
rheumatoid arthritis
renal transplants
solid tumors and
AIDS.

Pathogenesis

Kingella kingae is thought to begin infection by colonizing the pharynx, crossing the epithelium by using an RTX (repeat-in-toxin) toxin, superfamily is a group of cytolysins and cytotoxins, and entering the circulation and reaching deeper tissues, such as bones and joints.

Pathogenicity

Kingella causes-

septic arthritis
osteomyelitis
spondylodiscitis
bacteremia
endocarditis and
less frequently lower respiratory tract infections and meningitis.

Other species of Kingella– K. indologenes and K. denitrificans both are responsible for endocarditis whereas K. oralis found in dental plaque.

Laboratory Diagnosis of Kingella

Specimens- It may depend on the nature of the infection and the most common samples are respiratory secretions, blood, and bone, and joint exudates.

K. kingae has typical features for identification and they are-

Gram stain picture may have Gram-negative pairs or chains of 4 to 8 plump coccobacilli
Its colony on blood agar is beta-hemolytic.
It is oxidase test positive but catalase test negative.
Employing a real-time PCR assay that amplifies portions of the rtxA and rtxB genes.

Treatment

In the past, patients with central nervous system infections caused by Kingella kingae were treated with a penicillin drug alone or in combination with chloramphenicol, but currently, a third-generation cephalosporin i.e. cefotaxime or ceftriaxone as monotherapy or in combination with an aminoglycoside ( gentamicin or amikacin) for is preferred.

The empirical drug regimens for septic arthritis and osteomyelitis in young children generally combine the parenteral administration of a penicillinase-stable β-lactam antibiotic such as oxacillin and a broad-spectrum second-generation i.e cefuroxime or third-generation cephalosporin i.e. ceftriaxone.

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