Bacterial Culprit in Child Bone Infections May Lurk in the Throat

Bridget M. Kuehn

September 05, 2017

Many children with bone and joint infections also carry the causative bacteria in their throat, an observation that may aid in quicker diagnosis and more targeted treatment, according to a study published in the CMAJ.

Over the past 2 decades, Kingella kingae has become recognized as the leading cause of bone and joint infections among children under age 4 years, according to pediatric infectious disease experts Romain Basmaci, MD, PhD, and Stéphane Bonacorsi, MD, PhD, both from the Hôpital Louis-Mourier in Colombes, France, who coauthored an accompanying editorial. Previously, K kingae was hard to detect via traditional bacterial cultures and likely went undetected. Now, however, newer techniques, such as polymerase chain reaction assays, can detect the bacteria's DNA, making it easier to find.

"This highlights improved detection of K. kingae owing to molecular techniques, as well as awareness of clinicians and microbiologists, more than a real 'emergence' of the pathogen," the editorialists write.

Children often carry this pathogen in their throats. To determine whether such colonization was linked with bone and joint infections, Jocelyn Gravel, MD, MSc, a pediatric emergency physician at Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Quebec, Canada, and a multi-institution team of colleagues, conducted a case-control study at a pair of pediatric hospitals in Canada and Switzerland. The study included 77 children who presented to the hospitals' emergency departments with a likely diagnosis of osteoarticular infections and 286 matched controls presenting to the emergency department without such infections. 

Using polymerase chain reaction testing, the authors found K kingae in the throats of 46 of the 65 (71%) confirmed cases of bone or joint infections and 17 of 286 controls (6%). The risk of having a bone infection was dramatically higher among children who carried K kingae (odds ratio, 38.3; 95% confidence interval, 18.5 - 79.1).

This finding suggests that testing throat samples for this pathogen may help diagnose the cause of a bone and joint infection. It also might help guide treatment because K kingae is often resistant to clindamycin and cases of β-lactam resistance have been reported, write the authors.

"Based on this study, we plan to change the way we investigate children at risk of bone/joint infection, because the identification of K. kingae in the throat of a child with a suspected bone infection will point towards K. kingae as the culprit," said Dr Gravel in a press release. "This may decrease the number of other tests performed to identify the pathogen."

The authors caution, however, that larger multicenter studies in North America are needed to confirm the prevalence of bone and joint infections in children who carry K kingae.

The editorial authors write that "with a carriage rate [of K kingae] among healthy children as high as 10% in some countries, relying on oropharyngeal detection as a proxy for diagnosis in the case of a joint infection would result in a high [rate of] false-positive diagnosis."

They also write that while the throat is thought to be the point of entry for invasive bacterial infections, the role of K kingae colonization in pathogenesis isn't yet clear. Some studies suggest that colonization plus a viral infection may be required for an invasive infection to occur, they note. Evidence that invasive K kingae infections are seasonal while carriage of the bacteria is not support this idea.

The editorialists suggest that additional testing, such as genotyping, capsule typing, or specific viral testing, might make oral testing for K kingae more useful.

The authors and editorial writers have disclosed no relevant financial relationships.

CMAJ. 2017;189:E1107-11, E1105-6. Abstract, Editorial  

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