Biofilms in periprosthetic orthopedic infections.

As the number of total joint arthroplasty and internal fixation procedures continues to rise, the threat of infection following surgery has significant clinical implications. These infections may have highly morbid consequences to patients, who often endure additional surgeries and lengthy exposures to systemic antibiotics, neither of which are guaranteed to resolve the infection. Of particular concern is the threat of bacterial biofilm development, since biofilm-mediated infections are difficult to diagnose and effective treatments are lacking. Developing therapeutic strategies have targeted mechanisms of biofilm formation and the means by which these bacteria communicate with each other to take on specialized roles such as persister cells within the biofilm. In addition, prevention of infection through novel coatings for prostheses and the local delivery of high concentrations of antibiotics by absorbable carriers has shown promise in laboratory and animal studies. Biofilm development, especially in an arthoplasty environment, and future diagnostic and treatment options are discussed.

A rabbit osteomyelitis model to simulate multibacterial war wound infections.

A challenge facing military caregivers is the presence of multidrug-resistant infection in extremity wounds. Most frequently identified resistant strains are methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae (KP), Pseudomonas aeruginosa (PA), and Acinetobacter baumannii (AB). We adapted an existing osteomyelitis model to simulate an infected extremity wound for antibiotic testing. New Zealand White Rabbits (n = 95) were divided into 6 inoculation groups for infection with MRSA, KP, PA, and AB alone, and in multibacteria infections. Sodium morrhuate was injected into the left tibia to simulate blast wound trauma, then the respective bacteria or combination of pathogens, and finally sterile saline were injected. Colony-forming units for the mono-organism groups showed that AB, KP, or PA alone at 10(7) colony-forming units per mL (CFUs/mL) was effective for rabbit osteomyelitis induction. Colony-forming units for the multiorganism groups showed that the combination of AB (10(7) CFUs/mL)/KP (10(7) CFUs/mL)/PA (10(7) CFUs/mL)/MRSA (10(5) CFUs/mL) yielded a 100% osteomyelitis induction rate. At 8 weeks, however, only one mono-bacterial group and one multibacterial group showed significant radiographic improvement (p < 0.05). The rabbit model of osteomyelitis can be adapted to study infected blast wounds typical of those seen in veterans. To our knowledge, this is the first demonstration of the model simulating multibacterial infections with multidrug-resistant organisms.