US researchers are looking into the use of the polymerase chain reaction (PCR) to improve the detection of the bacteria causing osteomyelitis, an infection of the bone, which could help in choosing the right antibiotic and monitoring the progress of the disease and its treatment.
Osteomyelitis, a long-term infection of the bone causing pain, inflammation, bone degradation and bone loss, affects both adults and children. It can be hard to treat, and chronic disease may need long-term antibiotic treatment and/or surgery. While fast and accurate diagnosis is a major factor in its successful treatment, traditional diagnostic tests may not be sensitive enough to pick up the infection and identify the bacteria in its early stages, especially in slowly-progressing chronic disease. This could mean delays in finding the best possible antibiotic to eradicate the infection.
In the study, published in the Journal of Experimental Orthopaedics, the researchers used a rabbit model of experimental chronic osteomyelitis, infected with Staphylococcus aureus. They tested for the infection after 28 days, comparing standard microbiological culturing with the use of PCR and qPCR to detect bacterial genomic DNA. The techniques used two sets of PCR primers, one for a universal bacterial gene (16S rRNA), which hybridises to the DNA of virtually all pathogenic bacteria for broad-spectrum detection. The other targeted a species-specific gene, the Staphylococcus aureus-specific heat stable nuclease gene (nuc).
The results showed that the PCR technique was both accurate and sensitive, picking up animals with low level disease that were not identified using either microbiological or radiographic tests. This suggests potential for finding early-stage disease, where antibiotic therapy could be most effective. This could be carried out in a number of phases, starting with a universal primer to detect bacterial infection and then a second, multiplex phase for species identification. This study used only the Staphylococcus aureus-specific heat stable nuclease gene, but tests could be broadened out to use species-specific primers that target other pathogens found in chronic osteomyelitis, including Streptococcus pyogenes and other Group A Streptococci, Hemophilus influenzae, Pseudomonas aeruginosa, Proteus, Bacteroides, and Staphylococcus epidermidis. Finally, according to the researchers, PCR could be used to assess antibiotic suscepitibility: “the viable bacteria load may be assessed using a reverse-transcription based PCR protocol that targets viability-sensitive bacterial mRNAs and 16S rRNA.”