Addition of fusidic acid impregnated bone cement to systemic teicoplanin therapy in the treatment of rat osteomyelitis

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

The use of bone cement for the localized, controlled release of the antibiotics vancomycin, linezolid, or fusidic acid: effect of additives on drug release rates and mechanical strength

Bone cement containing antibiotics is commonly used to treat orthopedic related infections. However, effective treatment (especially of resistant bacteria, methacillin-resistant Staphylococcus aureus (MRSA)) is compromised by very low levels of drug release so that typically less than 10% of loaded drug is released over a 6-week period. The objective of this study was to investigate the effect of incorporation of water soluble excipients (polyethylene glycol, sodium chloride, or dextran) into antibiotic-loaded cement on mechanical strength and drug release properties. Poly(methyl methylacrylate) cement implants containing various amounts of drug (vancomycin, linezolid or fusidic acid (all MRSA active)) and excipients were cast in the form of beads or films and characterized using differential scanning calorimetry. Mechanical strength as assessed by Young's modulus was determined by thermo-mechanical analysis. Drug release was measured by incubation in phosphate buffered saline with analysis by HPLC methods. The inclusion of sodium chloride up to 20% w/w caused only minor reductions in Young's modulus. Vancomycin and linezolid released very slowly from unmodified bone cement beads (less than 3% released by 4 weeks) whereas fusidic acid released more quickly (approximately 8% released by 4 weeks). The inclusion of sodium chloride or dextran in bone cement resulted in major increases in the release rate of vancomycin, linezolid and fusidic acid. These studies support the inclusion of sodium chloride and dextran in bone cement to increase the release rate of vancomycin, linezolid, or fusidic acid without compromising the mechanical strength of the composite material.

A systematic review of animal models for Staphylococcus aureus osteomyelitis

Staphylococcus aureus (S. aureus) osteomyelitis is a significant complication for orthopaedic patients undergoing surgery, particularly with fracture fixation and arthroplasty. Given the difficulty in studying S. aureus infections in human subjects, animal models serve an integral role in exploring the pathogenesis of osteomyelitis, and aid in determining the efficacy of prophylactic and therapeutic treatments. Animal models should mimic the clinical scenarios seen in patients as closely as possible to permit the experimental results to be translated to the corresponding clinical care. To help understand existing animal models of S. aureus, we conducted a systematic search of PubMed and Ovid MEDLINE to identify in vivo animal experiments that have investigated the management of S. aureus osteomyelitis in the context of fractures and metallic implants. In this review, experimental studies are categorised by animal species and are further classified by the setting of the infection. Study methods are summarised and the relevant advantages and disadvantages of each species and model are discussed. While no ideal animal model exists, the understanding of a model's strengths and limitations should assist clinicians and researchers to appropriately select an animal model to translate the conclusions to the clinical setting.

Combined Therapy of Teicoplanin and Caffeic Acid Phenethyl Ester (CAPE) in the Treatment of Experimental Mediastinitis in the Rat

Post-sternotomy mediastinitis affects 1-3% of patients undergoing cardiac surgery and is lethal in 10-47% of these patients. We investigated the effect of an antioxidant/anti-inflammatory agent, caffeic acid phenethyl ester (CAPE), in the attenuation of inflammatory response induced by methicillin-resistant Staphylococcus aureus (MRSA) infection in a rat experimental mediastinitis model. Rats, divided into six equal groups, received MRSA precolonized stainless steel wire pieces implanted into their mediastinal spaces. Control group and CAPE control group received saline and CAPE 10 micromol/kg.day(-1 )respectively, where Group A received a single dose of teicoplanin 24 mg/kg i.m. for the first day and then 12 mg/kg.day(-1) . Group B received teicoplanin as in Group A plus CAPE 10 micromol/kg. day(-1 )intra-peritoneally. Group C received teicoplanin 60 mg/kg i.m. for the first day and then 30 mg/kg.day(-1 )and Group D received teicoplanin as in Group C plus CAPE 10 micromol/kg.day(-1) . By the end of 14 days rats were sacrificed and serum malondialdehyde (MDA), myeloperoxidase (MPO), nitric oxide (NO), urea and creatinine levels were evaluated. Mediastinal organ tissues were collected for histopathological analysis. Infection rates in all the drug-treated groups were lower than the control groups ( P=0.002) but statistical significance was attained only between the groups A and D ( P=0.018). In connective tissues and the peribronchial area polymorphonuclear leukocytic (PNL) infiltration in the treatment groups, although becoming very close, did not reach statistical significance (P =0.053, P=0.075, respectively). PNL infiltration especially in the peribronchial tissues of the Group B animals was found to be significantly less than the Control and CAPE Control groups with P values of 0.013 and 0.010, respectively. MDA and MPO levels were significantly lower in the treatment groups ( P<0.001 and P<0.001 respectively). Levels of the degradation products of NO were lower in treatment groups compared to two control groups (P=0.003, P= 0.005). NO levels in Group D were lowest among all treatment groups ( P=0.001). It has been demonstrated that although bacterial colonization can be controlled in mediastinitis, the inflammatory response persists. The combination of an antioxidant / anti-inflammatory agent, CAPE, added to standard antibiotic therapy might be effective in the treatment of post-sternotomy mediastinitis due to MRSA.

A RAT MODEL OF POLYPROPYLENE GRAFT INFECTION CAUSED BY STAPHYLOCOCCUS EPIDERMIDIS

BACKGROUND

The aim of this study was to constitute a valid graft infection model with Staphylococcus epidermidis in rats.

METHODS

Rats were divided into seven groups. In groups 1 and 2, 2 cm x 2 cm polypropylene grafts were incubated with 10(8) c.f.u./mL slime-positive S. epidermidis at 37 degrees C for 2 and 24 h and were then placed subfascially to the groins of rats. In the third group, naive grafts were placed and 0.5 mL of 3 x 10(7) c.f.u. slime-positive S. epidermidis were injected on the inside of the wounds. Rifampicin (30 mg/kg) in group 4 and teicoplanin (20 mg/kg) in group 5 were applied i.p. to rats with 2-h incubated grafts for prophylaxis. The same prophylactic regimens were given to groups 6 and 7 in which rats were incubated for 24 h. At eighth day, rats were killed and wounds were assessed with macroscopic evaluation and cultures.

RESULTS

No death occurred in any of the groups. In groups 1 and 2, 100% infection rates were achieved. However, graft infection was detected in only two (20%) of the rats in group 3 (P = 0.001). Prophylactic application of teicoplanin or rifampicin decreased the infection rates significantly in the short-incubation groups.

CONCLUSION

Incubation of polypropylene grafts with slime-producing S. epidermidis for 2 and 24 h in the pre-application period achieved the occurrence of a standardized graft infection. Prophylactic use of teicoplanin and rifampicin decreased the infection rates. We propose to use this reproducible and reliable animal model of graft infection in future studies.

Efficacy of Vancomycin, Teicoplanin and Fusidic Acid as Prophylactic Agents in Prevention of Vascular Graft Infection: An Experimental Study in Rat

OBJECTIVES

To compare the efficacy of a single prophylactic dose of intra-peritoneal vancomycin and teicoplanin with anti-biotic treated Dacron grafts (vancomycin, teicoplanin, 10 or 40% fusidic acid-soaked grafts) in preventing vascular graft infections in a rat model.

DESIGN

Prospective, randomized, controlled animal study.

MATERIALS AND METHODS

The graft infections were established in the subcutaneous tissues of 80 female Sprague-Dawley rats by the implantation of Dacron prostheses followed by the topical inoculation with methicillin-resistant Staphylococcus aureus. The study groups were as follows: (1) uncontaminated control group, (2) untreated contaminated group, (3) contaminated group with intra-peritoneal vancomycin, (4) contaminated group with intra-peritoneal teicoplanin, (5) contaminated group received vancomycin-soaked Dacron graft, (6) contaminated group received teicoplanin-soaked Dacron graft, (7) contaminated group received 40% fusidic acid-soaked Dacron graft, and (8) contaminated group received 10% fusidic acid-soaked Dacron graft prophylaxis. The grafts were removed after 7 days and evaluated by a quantitative culture analysis.

RESULTS

No infection was detected in controls. The untreated contaminated group had a high bacteria count (6.0 x 10(4) CFU/cm2 Dacron graft). Groups that received intra-peritoneal vancomycin or teicoplanin had less bacterial growth (4.8 x 10(3) and 3.9 x 10(3)CFU/cm2 Dacron graft, respectively). Similarly, the group that received 10% fusidic acid-soaked graft showed less bacterial growth (3.6 x 10(3) CFU/cm2 Dacron graft). The groups with vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts showed no evidence of infection. Statistical analyses demonstrated that intra-peritoneal prophylactic antibiotic treatment was less effective in inhibiting bacterial growth than high concentration antimicrobial-soaking of grafts.

CONCLUSION

The use of vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts was effective in preventing primary prosthetic vascular graft infection.