Influence of bacteria on spinal implant-centered infection: an in vitro and in vivo experimental comparison between Staphylococcus aureus and mycobacterium tuberculosis.

STUDY DESIGN:an in vitro and in vivo experimental study. OBJECTIVE:this study was undertaken to evaluate differences in the capability of inducing an implant-centered infection between Staphylococcus aureus and Mycobacterium tuberculosis. SUMMARY OF BACKGROUND DATA:bacterial infection is still one of the most serious and devastating complications after orthopedic implant surgery despite the advent of new antibiotics and treatment methods. METHODS:S. aureus and M. tuberculosis were separately cultured with titanium plates. The bacteria colonized on the plates were isolated and cultured on culture medium. They were evaluated and compared by colony-forming units enumeration. Scanning electron microscopy was used to evaluate the difference in the colonization features of the 2 pathogens. In the in vivo experiment, 22 dogs were used to assess the susceptibility to infection after a local bacterial challenge with either S. aureus or M. tuberculosis. RESULTS:S. aureus showed heavy adhesion and multiplication on the surface of titanium plates in vitro, whereas M. tuberculosis rarely adhered to the surface of the plates. Under scanning electron microscopy, S. aureus colonization was observed: the coccoid was widespread on the surface of the plates but only a few M. tuberculosis cells scattered on the surface of the plates. In in vivo test, the infection rateforthe S. aureus inoculation was higher than that for the M. tuberculosis challenge. The infection rate for the entire test population (n = 44 sites) was 39.58% (19/48). The infection rates were 54.17% (13/24) for the S. aureus challenge and 25% (6/24) for the M. tuberculosis challenge, respectively (P < 0.05). CONCLUSION:it is less likely for M. tuberculosis to adhere and form a biofilm on an implant surface than S. aureus. Under otherwise identical conditions, M. tuberculosis contamination following instrumented spine surgery might lead to less occurrence of infection than S. aureus contamination.