Kingella are small, gram-negative bacteria that are part of the normal human oropharyngeal flora. Kingella kingae in particular is an emerging pathogen in young children that can cause invasive infections like septic arthritis, osteomyelitis, and endocarditis. It is identified through culture on selective media and confirmed with biochemical and molecular testing. Treatment involves beta-lactam antibiotics for several weeks depending on the site of infection. While often part of normal flora, K. kingae can opportunistically cause serious disease in young children.

1. kingella
By- Sanju Sah
St. Xavier’s College, Maitighar, Kathmandu
Department of Microbiology

2. CLASSIFICATION
Domain: Bacteria
phylum: Proteobacteria
Class : Betaproteobacteria
Order : Nesseriales
Family : Neisseriaceae
Genera : kingella

3. INTRODUCTION
• kingella are small gram-negative, capnophilic and facultatively anaerobic .
• First isolated in 1960 by Elizabeth O. King but was not recognized as a significant cause of infection in young
children until the 1990s,
• The genus currently comprises five species: Kingella denitrificans, Kingella oralis, Kingella potus,
Kingella kingae and (most recently) K. negevensis .
• It is best known as a cause of septic arthritis, osteomyelitis, spondylodiscitis, bacteraemia, and
endocarditis, and less frequently lower respiratory tract infections and meningitis.
• K. kingae is the fifth member of the HACEK group of fastidious Gram-negative bacteria that cause endocarditis.

4. INTRODUCTION
Four species:
• Kingella denitrificans - a rare cause of endocarditis, pediatric vaginitis.
• Kingella kingae – emerging invasive pathogen of young children.
• Kingella oralis – periodontitis
• Kingella potus – isolated from wound caused by an animal bite.

5. CHARACTERISTICS
• Kingella kingae is a gram-negative bacterium and a member of the normal flora of the
oropharynx.
• They appear as pairs or chains of 4 to 8 plump (0.6 to 1 μm by 1 to 3 μm) coccobacilli .
• The bacterium is beta-hemolytic, non-motile, and non-spore forming with tapering ends.
• Kingella kingae cells tend to resist decolorization, and thus the organism may be erroneously
identified as Gram positive.

7. GROWTH AND PHYSIOLOGY
• Grows slowly on chocolate agar and blood agar but not on mac conkey agar.
• Grows selectively on trypticase soy agar (contains 5-7% sheep blood and vancomycin
2µm/ml).
• Kingella kingae strains produce three different colony types that are associated with the degree
of pilus expression: a spreading-corroding morphology distinguished by a small central colony
encircled by a wide fringe, a nonspreading/noncorroding type consisting of a flat colony
surrounded by a narrow fringe, and a dome-shaped colony with no noticeable fringe. The first
two morphologies are associated with the presence of long fimbriae, whereas strains growing
as domed colonies are nonpiliated. The ability to produce the spreading-corroding type of
morphology can be irreversibly lost after repeated subculture.
• Kingella kingae produces acid from glucose and maltose but not from other sugars, hydrolyzes
indoxyl phosphate and l-prolyl-β-naphthylamide, and exhibits positive alkaline and acid
phosphatase reactions.

8. VIRULENCE FACTOR
• Pili
• Polysaccharide capsule
• RTX toxin
• Outer membrane

9. PATHOGENESIS
• Kingella initiates infection by colonizing the posterior pharynx.
• A key step in colonization of the respiratory tract is adherence to the respiratory epithelium.
• Kingella adherence to human epithelial cells is due to three surface factors:type IV pili, Knh
and the capsule.
• pilT/PilU-mediated pilus retracts and brings the bacterium into close contact with the host cell
causing physical displacement of the surface polysaccharide capsule.
• Once the capsule has been displaced, Knh is able to engage its host cell receptor, leading to
the high-level adherence.

10. PATHOGENESIS
• The organism then enters the bloodstream and disseminates to distant sites, including joints,
bones, and the endocardium.

12. CLINICAL MANIFESTATIONS
• Invasive K. kingae disease usually affects previously healthy children aged less than 4 years
• whereas older children and adults frequently have predisposing conditions such as failure to
thrive
 congenital heart disease
 primary immunodeficiency
 hematological malignancies
 liver cirrhosis
 end-stage renal disease
 sickle cell anemia
 diabetes mellitus , cardiac valve restriction, systemic lupus erythematosus, rheumatoid arthritis,
solid tumors.

13. LABORTORY DIAGNOSIS
SPECIMEN COLLECTION:
Blood, synovial fluid, and solid tissues, as well as in upper respiratory tract specimens,
restricted heart valves in case of infective endocarditis.
MEDIA USED: Blood agar, chocolate agar, Thayer-martin agar, BAV(selective media)
DIRECT DETECTION
• Gram staining of specimen reveals gram-negative coccobacilli that may appears in chain

14. Contd…
CULTURE PROCEDURE:
• Kingella are β-haemolytic and can grow on a selective and indicative culture medium
consisting of trypticase soy agar with 5% added sheep hemoglobin and 2µg/ml of vancomycin
(BAV medium).
• The glycopeptide antibiotic inhibits the growth of the competing gram-positive buccal and
pharyngeal flora whereas the aerobic conditions suppress the development of anaerobic species
and Co2 enhances the growth of capnophilic kingella.
• Plates are incubated under aerobic conditions in a 5% Co2 enriched environment at 35◦C for
48 hours.
• Sub-culture can be done on blood agar, chocolate agar and Thayer-martin media but not on
kliger and macconkey agar.

16. IDENTIFICATION
Identification of kigella can be done based on colony morphology and different biochemical tests:
CULTURAL IDENTIFICATION
Β-haemolysis
Kingella kingae is characterized by growth as pinpoint colonies with marked pitting of the agar
surface which is best seen after removal of the colony.
Kingella denitrificans produces small colonies , non-hemolytic, and frequently pits agar.
Biochemical identification
Catalase- Negative
Oxidase- negative(with rare exceptions, has oxidase activity)
Urease- negative
Indole- negative

18. MOLECULAR IDENTIFICATION
• PCR assay specific to k. kingae targets are ten fold more sensitive than broad-range 16s rRNA
gene PCR.
• NAA assay-The NAA assays targeting the RTX toxin genes (rtxA and/or rtxB).
 It is more sensitive than PCR tests that amplify the 16S rRNA gene or the cpn60 gene.
SEROLOGICAL IDENTIFICATION
• ELISA(Enzyme Linked immunosorbant Assay) - To detect antibodies against outer membrane
protein (OMP).

19. TREATMENT
• Drug therapy consists of the administration of β-lactam or a second –or-third generation
cephalosporin.
• Antibiotic treatment duration varies from 2 to 4 weeks for osteoarticular infections. 1 to 2
weeks for nonfocal bacteremia and 6 to 8 weeks for endocarditis.
• No treatment is currently recommended to eliminate the carriage state.

20. MEDICAL IMPORTANCE
• It is a fastidious group of organism.
• They are part of the normal upper respiratory and genitourinary tract flora of humans.
• It is the major cause of endocardities
• kingella kingae is also known as an important cause of invasive infections in young children.

21. REFERENCE
• https://cmr.asm.org/content/28/1/54
• https://www.sciencedirect.com/topics/medicine-and-dentistry/kingella-kingae
• https://en.wikipedia.org/wiki/Kingella_kingae
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2726550/

22. Thank you!!!