Objectives: The microbiological diagnosis of osteoarticular infections currently relies on microbiological cultures, to specifically target treatment. However, these conventional methods sometimes lack of sensitivity and of specificity to establish definitive diagnosis. This study was conducted to determine whether molecular method could improve bacterial bone and joint infection diagnosis.

Methods: We evaluated the performance of nucleic acid extraction with the semi-automated NucliSens miniMAG instrument coupled to 16S rDNA sequencing on 76 samples collected from 51 patients with suspected infections: prosthetic-joint infection (15), spondylodiscitis (7) acute septic arthritis (11) and 18 controls. No pre-treatment of the sample was done before nucleic acid extraction. Classification in infected group required an accumulation of arguments.

Results: Our molecular method identified a broad spectrum of pathogenic bacteria including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus faecalis, Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa, and fastidious bacteria like Neisseria gonorrhoeae and Fusobacterium nucleatum. The overall PCR sensitivity was 73.3%: 53.8% for prosthetic-joint infections and 88.2% for infections without prostheses. The overall PCR specificity was 95.2%, whereas culture specificity was only 85.7%.

Conclusions: The instrument was simple to use and provided nucleic acids free of PCR inhibitors and free of contamination by foreign bacterial DNA. Our study highlights the need for still improved molecular diagnostic sensitivity.