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Kingella kingae
a Potentially Emerging Pathogen: a Comprehensive Review
3
From being almost an established pathogen among
children,
Kingella kingae
has recently been reported to
cause invasive infections in adults. A case of
osteomyelitis pubis has been reported in an adult
patient aged 66 years, with underlying end stage
kidney disease and breast carcinoma (Wilmes et al.,
2012).
Prevalence and Colonization of
Kingella
kingae
Considering the fact that there has been an increase in
the incidences of invasive
Kingella kingae
infections
both in children and in adults, a recent study carried
out to assess the respiratory tract colonization and
revealed that 97% of the pharyngeal samples were
positive for
Kingella kingae
(Yagupsky, 2013). Sheep
Blood agar with 2 mg/mL vancomycin (BAV) was
used for the culture to increase the isolation rate which
acts as a selective medium by inhibiting the growth of
other Commensal gram positive bacteria (Yagupsky et
al., 1995; Basmaci et al., 2012). Previous studies have
confirmed that children below 6 months are not
colonized with
Kingella kingae
and that the
colonization rates vary among 6 months to 4 years
(10%) children and school going children (4~14 years)
(Goutzmanis et al., 1991). Yapupsky et al. (1995) in
their study have noted that as the age increases the rate
of colonization decreases with 3.2%, 1.5% and 0.8%
colonization of
Kingella kingae
in respiratory
secretions in children < 4 years old, 4~14 years and
adults respectively (Yagupsky, 2013). A study from
Switzerland, by Ceroni et al. (2012) which included
431 young asymptomatic young children used
real-time PCR for the detection of
Kingella kingae
from pharyngeal secretions and revealed a
colonization rate of 8.1% (Ceroni et al., 2012).
Previous studies have also confirmed the colonization
of
Kingella kingae
in respiratory secretion among
patients
with microbiologically confirmed
osteo-articular infections (Chometon et al., 2007).
Studies have also revealed that
Kingella kingae
colonization was observed more in the oropharynx
than in the nasopharynx confirming the fact that
Kingella kingae
occupies a rather narrow niche in the
upper respiratory tract (Yagupsky et al., 2002).
Reports have also indicated that there is an increased
colonization and infection rates among day-care
attendees,
suggestive of overcrowding as a
predisposing factor for person-to-person spread
(Robinson, 2001).
Studies on molecular typing with PFGE have
confirmed that spread of
Kingella kingae
is associated
with close mingling as seen among family members,
playmates and community gatherings which should be
considered as a predisposing factor for exposure
(Yagupsky et al., 2009).
Determinants of Colonization and Invasive
Properties
Microbial entry in to the human is very common but
for it to cause infection/disease, the microbe should be
able to adhere, adapt and invade. Pili are the surface
projections present on the bacterial cell wall that help
the organism to adhere. Studies have confirmed that
Kingella kingae
possesses type IV pili which play a
key role in attachment to the respiratory epithelial
cells and synovial cells (Kehl-Fie et al., 2008). Studies
have also revealed certain genes (
pilA1
,
pilA2
,
fimB
,
pilS
,
pilR
,
pilC1
,
pilC2
), that are coding for the
expression of pili in
Kingella kingae
and have noted
that strains isolated from colonized persons had pili
and those isolated from invasive infections were
non-piliated indicating that the process of piliation is
self regulating and influenced by immune response
(Kehl-Fie et al., 2010). Another protein, a trimeric
autotransporter protein called
Knh
also helps
Kingella
kingae
to firmly bind to the colonization sites (Porsch
et al., 2012).
Kingella kingae
, has the property to form
biofilms (ability of microorganisms to produce a
polymeric matrix like substance surrounding them to
evade immune response and antibiotics entry), that
helps in colonization and periodic dispersion of
bacteria to other parts of the host and enabling the
bacteria to evade immune detection, dessication and
antimicrobial action; it has also been noted that
Kingella kingae
has an anti-biofilm activity that
prevents other bacterial colonization and there by
establishing itself in the respiratory mucosa
(Bendaoud et al., 2011). A toxin named RTX was
identified as an exotoxin that is coded on the
Kingella
Molecular Pathogens