Effectiveness of bone cement containing tobramycin - An in vitro susceptibility study of 99 organisms found in infected joint arthroplasty

We used 99 strains of organisms representative of orthopaedic infections to examine the effectiveness of a bone cement containing tobramycin, employin g a modified in vitro Kirby-Bauer susceptibility model. The spectrum was br oad, including Gram-positive and Gram-negative aerobic organisms, anaerobes and mycobacteria, Simplex P with added tobramycin was effective against mo st of the strains, including those which are resistant to typical systemic levels of tobramycin, Although direct correlation between in vitro and in v ivo results is difficult, the study showed that tobramycin is stable to the exothermic polymerisation of the cement, and that it is released from the surface of the cement at concentrations high enough to inhibit the growth o f most organisms which may be encountered after joint arthroplasty.