This study investigated using a real-time PCR test targeting the RTX toxin gene of Kingella kingae on oropharyngeal swabs to diagnose K. kingae osteoarticular infections (OAI) in young children. The prospective study of 123 children aged 6-48 months presenting with atraumatic joint complaints found the oropharyngeal PCR test had a sensitivity of 100% and specificity of 90.5% for diagnosing K. kingae OAI compared to MRI and culture results. The findings suggest K. kingae is the primary cause of OAI in young children and that oropharyngeal PCR could improve recognition of these difficult to diagnose infections.

2.  Major cause of osteoarticular infections (OAI) in
children under 4 years.
 Belongs to the normal oropharyngeal flora (8-9%
asymptomatic carriers)
 Colonization of the oropharynx is a prerequisite for
invasive infections which is mediated by the
production of a potent RTX cytotoxin.
 However diagnosing OAI caused by K. kingae remain
challenging (mild clinical, biological and radiological
signs and difficult germ cultivation).
Kingella kingae:

3. Study Aim
 To investigate whether a specific oropharyngeal swab real time
PCR (oropharyngeal K. kingae PCR) could improve the recognition
of K. kingae OAI in young children.

Specific real time PCR targeting the
RTX toxin coding DNA of K. kingae

4.  Prospective cohort study of all young children presenting with atraumatic
osteoarticular complaints between 2008 and 2011 to our emergency room.
Enrolment
Clinical evaluation
1st phase investigations
2nd phase
diagnostic investigations
• Atraumatic OA
complaints
• Age 6-48 months
• Clinical evaluation
• CBC, CRP, VS, blood culture
• Oropharyngeal K. kingae PCR
• MRI • Infection site puncture
• Culture, broad range PCR
• K. kingae PCR on osteo-
articular aspirate
Findings suggestive for OAI

5. K. kingae OAI
30 cases
OAI (other)
1 case
no OAI
83 cases
H. Influenzae
123 patients enrolled
30 orophary. K.
kingae PCR +
MRI consistent with OAI
despite negative
microbiology
suspected OAI
9 cases
8 orophary. K.
kingae PCR +
76 orophary. K.
kingae PCR -
9 orophary. K.
kingae PCR +
Excluded from statistical analysis

6. Diagnostic performances of the oropharyngeal swab K. kingae specific PCR test (95% CI)
Sensitivity 100% (88.4; 100)
Specificity 90.5% (82.1; 95.8)
Positive predictive value 78.9% (62.7; 90.4)
Negative predictive value 100% (95.5; 100)

7.  K. kingae is the 1st microorganism responsible for OAI in children
under 4 years (>95% in this study)
 Detection of K. kingae DNA in oropharyngeal swabs of children with
clinical findings of OAI is predictive for K kingae OAI and negative
result excludes OAI caused by this bacteria.
 A valuable non invasive diagnostic tool which may improve the
recognition of K. kingae OAI among young children.

8.  Implementation of oropharyngeal K.kingae PCR as diagnostic tool
for OAI in our setting:
 Changed our diagnostic approach
 Faster recognition of OAI in young children
 Improved therapeutic management
 Increased recognition of OAI due to K. kingae

9. Thank you for your
attention