Staphylococcus caprae bone and joint infections: a re-emerging infection?

Staphylococcus caprae has been recently classified as a human pathogen, but the incidence of S.caprae in human bone and joint infections (BJIs) is under-reported. In this study, we report 25 cases of S.caprae BJI, and we review the 31 cases published in the literature. Molecular techniques and matrix-assisted laser desorption ionization time-of-flight mass spectrometry improved the identification of clinically relevant S.caprae strains. In this study, 96% of S.caprae BJIs were localized to the lower limbs, and 88% of the cases involved orthopaedic device infections. S.caprae joint prosthesis infections (JPIs), internal osteosynthesis device infections (I-ODIs) and BJIs without orthopaedic device infections were recorded in 60%, 28% and 12% of cases, respectively. Ten (40%) S.caprae BJIs were polymicrobial infections. These infections were associated with past histories of malignancy (p0.024). Of the 14 bacterial species related to S.caprae BJI, 57% were staphylococci. I-ODIs were significantly associated with polymicrobial infections (p0.0068), unlike JPIs, which were monomicrobial infections (p0.0344). Treatment with rifampicin and fluoroquinolone was recorded in 40% of cases. Surgical treatment was performed in 76% of cases, e.g. prosthesis removal (36%), osteosynthesis device removal (24%), and surgical debridement (16%). Thirty percent of cases were not treated. Relapses were observed mainly in the patients treated by surgical debridement only (p0.033). In summary, S.caprae BJI is an underestimated hospital-acquired emerging infection. S.caprae BJI is correlated with infections in orthopaedic devices, which must be removed to control the infection.