Gentamicin and clindamycin antibiotic-eluting depot technology eradicates <i>S. aureus</i> in an implant-associated osteomyelitis pig model without systemic antibiotics

The therapeutic challenges of orthopedic device-related infections and emerging antimicrobial resistance have attracted attention to drug delivery technologies. This study evaluates the preclinical efficacy of local single- and dual-antibiotic therapy against implant-associated osteomyelitis (IAO) using a drug-eluting depot technology, CarboCell, that provides sustained release of high-dose antibiotics and allows for strategic <i>in situ</i> placement in relation to infectious lesions. Clindamycin and gentamicin were formulated in CarboCell compositions. One-stage-revision of tibial <i>Staphylococcus aureus</i> IAO was conducted in 19 pigs. Pigs were treated locally with CarboCell containing either gentamicin alone for 1 week or a co-formulation of gentamicin and clindamycin for 1 or 3 weeks. Bone, soft tissue, and antibiotic depots were collected for microbiology, histology, and HPLC analyses. Supporting <i>in vivo</i> release studies of CarboCell formulations were performed on mice. Both single- and dual-antibiotic CarboCell formulations were developed and capable of eradicating the infectious bacteria in bone and preventing colonization of implants inserted at revision. Eradication in soft tissue was observed in all pigs after 3 weeks and in 6/9 pigs after 1 week of treatment. Neutrophil counts in bone tissue were below the infection cut-off in all pigs receiving the dual-antibiotic therapies, but above in all pigs receiving the single-antibiotic therapy. Histological signs of active bone reorganization and healing were observed at 3 weeks. In conclusion, all CarboCell formulations demonstrated strong therapeutic activity against IAO, eradicating <i>S. aureus</i> in bone tissue and preventing colonization of implants even without the addition of systemic antibiotic therapy.