PCR beneficial in diagnosing bone and joint infection
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Data from a 4-year study conducted in one French facility suggest that PCR is a beneficial “add-on” to routine culture to diagnose patients with a suspected bone and joint infection.
Between November 2007 and October 2011, researchers conducted a prospective study at Lariboisière University Hospital in Paris that included patients with suspected infectious spondylodiscitis, septic arthritis and prosthetic joint infections, as well as respective noninfected groups.
They collected clinical and radiological data at the start of the study and during follow-up, and tested samples by conventional culture and using 16S rDNA PCR (16S-PCR). They also tested the samples of spondylodiscitis using cultures and PCR targeting Mycobacterium tuberculosis (MT-PCR). An expert committee confirmed or rejected suspicion of infections and classified patients into the case or control group.
The final analysis included 105 bone and joint infections (BJI) and 111 controls. According to the study, 30% of pathogens detected were staphylococci, 19% were M. tuberculosis and 14% were streptococci.
For diagnosing M. tuberculosis spondylodiscitis, culture alone demonstrated 42.2% sensitivity. With the addition of a PCR test to culture, sensitivity increased to 64.4% (P < .01). Similarly, for nonstaphylococci BJI diagnoses, culture alone demonstrated 71.3% sensitivity compared with 81.6% for culture with PCR (P < .01).
Moreover, 16S-PCR detected BJIs that were caused by uncommon bacteria, including Mycoplasma and fastidious bacteria, which the researchers noted as being interesting.
“In case of high suspicion of bone and joint infection, 16S-PCR must be considered, particularly when cultures remain negative, keeping in mind that performance depends on the pathogens involved,” the researchers wrote. “New technologies, such as microarrays and next generation sequencing, are promising approaches for the diagnosis of BJI and must be assessed with similar clinical definitions of infected patients and controlled trials.” – by Marley Ghizzone
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Angela Hewlett, MD, MS
Adding PCR to routine cultures enhanced the sensitivity for diagnosis of spondylodisciitis due to Mycobacterium tuberculosis (64% vs. 42%) and nonstaphylococcal bone and joint infection (81% vs. 71%).Bone and joint infections may be difficult to diagnose and even more difficult to manage, and determining the causative microorganism is paramount to successful medical and surgical treatment of these complex infections. Culture yield may be influenced by the presence of fastidious or difficult-to-grow organisms, prior antibiotic exposure, sampling limitations and other factors. Culture-negative bone and joint infections are a source of frustration, and these patients are typically managed empirically with broad spectrum antibiotics, which may or may not result in eradication of the infection.
There is significant interest in methods other than traditional culture to identify causative microorganism, including molecular methods like 16S-PCR, however, there is considerable variation reported in the literature regarding the yield of PCR.
The findings in this study support the use of 16S-PCR for patients with nonstaphylococcal bone and joint infections and spondylodiscitis due to M. tuberculosis. Although the majority of bone and joint infections are caused by staphylococci, clinicians may choose to utilize PCR in select patients with culture-negative infections, those infected with organisms other than staphylococci, and especially in areas known to have a high incidence of M. tuberculosis. Accurate microbiologic diagnosis of these infections could change antimicrobial or surgical management and potentially influence clinical outcomes.
PCR is currently being utilized by many centers as an adjunct to traditional culture methods. The orthopedic infectious diseases community certainly welcomes any additional tools to aid in the diagnosis and management of bone and joint infections, and this study adds to our knowledge on the utility of PCR.
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