Single-dose bone pharmacokinetics of vancomycin in a porcine implant-associated osteomyelitis model

Dynamic distribution of systemically administered antibiotics in orthopeadically relevant target tissues and settings

This review aimed to summarize the current literature on antibiotic distribution in orthopedically relevant tissues and settings where dynamic sampling methods have been used. PubMed and Embase databases were systematically searched. English-published studies between 2004 and 2024 involving systemic antibiotic administration in orthopedically relevant tissues and settings based on dynamic measurements were included. In total, 5385 titles were identified. After title and abstract screening, 97 eligible studies (43 different antibiotic drugs) were included. The studies covered both preclinical (42%) and clinical studies including healthy and infected tissues (21%) and prophylactic and steady-state situations (35%). Microdialysis emerged as the predominant sampling method in 98% of the studies. Most of the presented antibiotics (80%) were only assessed once or twice. Among the most extensively studied antibiotics were cefuroxime (18 studies), linezolid (9 studies) and vancomycin (9 studies). This review presents valuable insights into the microenvironmental distribution of antibiotics in orthopedically relevant target tissues and settings and seeks to provide a basis for improving dosing recommendations and treatment outcomes. However, it is important to acknowledge that our findings are limited to the specific drug, dosing regimens, administration method and target tissue, and are crucially linked to the selected PK/PD target.

Penicillin concentrations in oropharyngeal and frontal sinus tissue following enteral and intravenous administration measured by microdialysis in a porcine model

BACKGROUND

Penicillin may be administered enterally or intravenously for the treatment of bacterial infections within the oropharynx and the frontal sinuses. We aimed to assess and compare penicillin concentrations in oropharyngeal and frontal sinus tissues following enteral and intravenous administration in a porcine model.

METHOD

Twelve pigs were randomized to receive either enteral (0.8 g Penicillin V) or intravenous (1.2 g Penicillin G) penicillin. Microdialysis was used for sampling in oropharyngeal and frontal sinus tissues during a six-hour dosing interval. In addition, plasma samples were collected. The primary endpoints were time with drug concentration above the minimal inhibitory concentration (T>MIC) for two MIC targets: 0.125 (low target) and 0.5 (high target) μg/mL (covering Group A Streptococci, Fusobactarium necrophorum, Streptococcus pneumoniae and Hemophilus influenza) and attainment of these treatment targets for ≥50 % T>MIC.

RESULTS

For both the low and high MIC targets, intravenous administration resulted in higher T>MIC in oropharyngeal and frontal sinus tissues compared to enteral administration. In oropharyngeal tissue, the treatment target (≥50 % T>MIC) was achieved for both the low target (96 %) and high target (68 %) when penicillin was administrated intravenously. In frontal sinus tissue, the treatment target was reached for the low target (70 %), but not the high target (35 %) when administered intravenously. None of the two tissues reached the treatment targets when penicillin was administered enterally.

CONCLUSION

Intravenous administrated penicillin in standard dosage is superior to enteral administration of penicillin in standard dosage in achieving clinically important T>MIC as the majority of targets were achieved following intravenously administration, while none of the targets were achieved following enteral administration. These results support the general notion of higher tissue concentrations following intravenous compared to enteral administration.

Eradication of Staphylococcus aureus in Implant-Associated Osteomyelitis by an Injectable In Situ-Forming Depot Antibiotics Delivery System

BACKGROUND

Bone infections with Staphylococcus aureus are notoriously difficult to treat and have high recurrence rates. Local antibiotic delivery systems hold the potential to achieve high in situ antibiotic concentrations, which are otherwise challenging to achieve via systemic administration. Existing solutions have been shown to confer suboptimal drug release and distribution. Here we present and evaluate an injectable in situ-forming depot system termed CarboCell. The CarboCell technology provides sustained and tuneable release of local high-dose antibiotics.

METHODS

CarboCell formulations of levofloxacin or clindamycin with or without antimicrobial adjuvants cis-2-decenoic acid or cis-11-methyl-2-dodecenoic acid were tested in experimental rodent and porcine implant-associated osteomyelitis models. In the porcine models, debridement and treatment with CarboCell-formulated antibiotics was carried out without systemic antibiotic administration. The bacterial burden was determined by quantitative bacteriology.

RESULTS

CarboCell formulations eliminated S. aureus in infected implant rat models. In the translational implant-associated pig model, surgical debridement and injection of clindamycin-releasing CarboCell formulations resulted in pathogen-free bone tissues and implants in 9 of 12 and full eradication in 5 of 12 pigs.

CONCLUSIONS

Sustained release of antimicrobial agents mediated by the CarboCell technology demonstrated promising therapeutic efficacy in challenging translational models and may be beneficial in combination with the current standard of care.

The efficacy of vancomycin-loaded biphasic calcium phosphate bone substitute in the promotion of new bone growth and the prevention of postoperative infection

Background: Due to the increasing need for suitable alternatives to bone grafts, artificial bones made of biphasic calcium phosphate (BCP) are currently being extensively researched. These porous bone substitutes have also demonstrated considerable incorporation with the host bone, and new bone is able to grow within the porous structure. They therefore offer a potential therapeutic approach for bone defects.

Methods: Vancomycin-loaded Bicera™, a BCP bone substitute, was investigated in order to prevent implant-associated osteomyelitis and postoperative infection after orthopedic surgery. The loading capacity of Bicera™ was measured to understand its potential antibiotic adsorption volume. An antibiotic susceptibility test was also carried out to analyze the effect of Bicera™ loaded with different concentrations of vancomycin on the growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin-loaded Bicera™ was implanted into rabbits with bone defects, and general gross, radiographic, and histological evaluation was undertaken at 4, 12, and 24 weeks after implantation.

Results: The maximum loading capacity of vancomycin-loaded Bicera™ was 0.9 ml of liquid regardless of the vancomycin concentration. Antibiotic susceptibility tests showed that vancomycin-loaded Bicera™ inhibited the growth of MRSA for 6 weeks. In addition, animal studies revealed that new bone grew into the vancomycin-loaded Bicera™. The percentage of new bone formation from 4 to 24 weeks after implantation increased from 17% to 36%.

Conclusion: Vancomycin-loaded Bicera™ could effectively inhibit the growth of MRSA in vitro. It was found to incorporate into the host bone well, and new bone was able to grow within the bone substitute. The results of this study indicate that vancomycin-loaded Bicera™ is a potential bone substitute that can prevent implant-associated osteomyelitis and postoperative infection.

Intermittent Short-Term Infusion vs. Continuous Infusion of Piperacillin: Steady State Concentrations in Porcine Cervical Spine Tissue Evaluated by Microdialysis

Background: Piperacillin is a central drug in the treatment of Pseudomonas aeruginosa spondylodiscitis. Intermittent short-term infusion (STI) remains standard treatment in most centres, although the application of continuous infusion (CI) has shown promising results in other clinical settings. We aimed to evaluate time above the minimal inhibitory concentration (fT > MIC) of the free fraction of piperacillin in steady state conditions in porcine cervical spine tissue following CI and STI using microdialysis with MIC targets of 4, 8, and 16 μg/mL. Methods: 16 female pigs were randomized to receive piperacillin/tazobactam as STI (4/0.5 g every 6 h) or CI (4/0.5 g as a bolus followed by 12/1.5 g) for 18 h. Microdialysis catheters were placed for sampling of piperacillin concentrations from the intervertebral disc, vertebral cancellous bone, paravertebral muscle, and adjacent subcutaneous tissue during the third dosing interval (12−18 h). Blood samples were collected as reference. Results: CI resulted in fT > MIC > 82% across all compartments and targets, except for intervertebral disc (37%) and vertebral cancellous bone (28%) at MIC = 16 μg/mL. In Group STI, >72% fT > MIC was reached for MIC = 4 μg/mL in all investigated compartments, while for MIC = 16 μg/mL only subcutaneous tissue exhibited fT > MIC > 50%. Conclusion: CI of piperacillin resulted in higher fT > MIC compared to STI infusion across the investigated tissues and targets. CI should therefore be considered in spondylodiscitis cases requiring piperacillin treatment.

Steady-state concentrations of flucloxacillin in porcine vertebral cancellous bone and intervertebral disc following oral and intravenous administration assessed by microdialysis

AIMS

Flucloxacillin is a frequently used antibiotic in the treatment of spondylodiscitis. We assessed steady-state concentrations and time above minimal inhibitory concentration (fT > MIC) of flucloxacillin in the intervertebral disc, vertebral cancellous bone, subcutaneous tissue and plasma, after intravenous and oral administration.

METHODS

Sixteen pigs were randomized into two groups; Group Peroral (Group PO) and Group Intravenous (Group IV) received 1 g flucloxacillin every 6 h for 24 h orally or intravenously. Microdialysis was used for sampling in the compartments of interest. A flucloxacillin target of 50% fT > MIC was applied for three MIC targets: 0.125, 0.5 and 2.0 μg/mL.

RESULTS

Intravenous administration resulted in significantly longer fT > MIC for all targets. Target attainment was only reached for the low target of 0.125 μg/mL in Group IV in vertebral cancellous bone, subcutaneous tissue, and plasma (intervertebral disc 47%). In Group IV, mean fT > MIC values in the investigated compartments were in the range of 47-67% of the dosing interval for 0.125 μg/mL, 20-35% for 0.5 μg/mL, and 0-15% for 2.0 μg/mL. In Group PO, mean fT > MIC values for 0.125 μg/mL were in the range of 1-33%. No pigs reached a concentration of 0.5 μg/mL in any of the investigated compartments in Group PO.

CONCLUSION

Administration of 1 g flucloxacillin every 6 h resulted in surprisingly low steady-state fT > MIC after intravenous and oral administration. However, intravenous administration resulted in significantly higher concentrations across compartments compared to oral administration. Sufficient target tissue concentrations for treatment of spondylodiscitis may require a dose increase or alternative dosing regimens.

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

Osteomyelitis is an inflammatory bone disease typically caused by infectious microorganisms, often bacteria, which causes progressive bone destruction and loss. The most common bacteria associated with chronic osteomyelitis is Staphylococcus aureus. The incidence of osteomyelitis in the United States is estimated to be upwards of 50,000 cases annually and places a significant burden upon the healthcare system. There are three general categories of osteomyelitis: hematogenous; secondary to spread from a contiguous focus of infection, often from trauma or implanted medical devices and materials; and secondary to vascular disease, often a result of diabetic foot ulcers. Independent of the route of infection, osteomyelitis is often challenging to diagnose and treat, and the effect on the patient's quality of life is significant. Therapy for osteomyelitis varies based on category and clinical variables in each case. Therapeutic strategies are typically reliant upon protracted antimicrobial therapy and surgical interventions. Therapy is most successful when intensive and initiated early, although infection may recur months to years later. Also, treatment is accompanied by risks such as systemic toxicity, selection for antimicrobial drug resistance from prolonged antimicrobial use, and loss of form or function of the affected area due to radical surgical debridement or implant removal. The challenges of diagnosis and successful treatment, as well as the negative impacts on patient's quality of life, exemplify the need for improved strategies to combat bacterial osteomyelitis. There are many in vitro and in vivo investigations aimed toward better understanding of the pathophysiology of bacterial osteomyelitis, as well as improved diagnostic and therapeutic strategies. Here, we review the role of animal models utilized for the study of bacterial osteomyelitis and their critically important role in understanding and improving the management of bacterial osteomyelitis.

Antibiotic-Loaded MMT/PLL-Based Coating on the Surface of Endosseous Implants to Suppress Bacterial Infections

BACKGROUND

Bone infections remain one of the most common and serious complications of orthopedic surgery, posing a tremendous economic burden to society and patients. This is because bacteria colonize and multiply on the surface of the implant. The (MMT/PLL)8 multilayer films have been shown to effectively release antibiotics depending on the changes in the microenvironment. Here, vancomycin was loaded into the (MMT/PLL)8 multilayer films, which were prepared to be used as a local delivery system for the treatment of bone infections.

METHODS

We used the layer-by-layer self-assembly method to prepare VA-loaded coatings (MMT/PLL-VA)8 consisting of montmorillonite (MMT), poly-L-lysine (PLL), and VA. The thickness and surface morphology of coatings were characterized using spectroscopic ellipsometry and scanning electron microscopy (SEM). In order to evaluate the drug release behavior from coatings in different media, we measured the size of the zone of inhibition. Additionally, in vitro antibacterial activity was assessed using the shake-flask culture method and SEM images, while that of in vivo was evaluated by establishing an animal model of bone infection.

RESULTS

Our findings revealed that small-molecule antibiotics were successfully loaded into the (MMT/PLL-VA)8 multilayer film structure during the hierarchical self-assembly process and subsequently the multilayer film structure depicted linear growth behavior. The PLL in the multilayer films was progressively degraded which triggered the VA release when contacted with CMS or bacterial infections. The release of VA from multilayer film structure depends on the concentration changes of CMS. Notably, the multilayer films presented great in vitro cell compatibility. Moreover, the prepared antibacterial multilayer films showed excellent antibacterial property by killing more than 99.99% of S. aureus in 24 h. More importantly, we found that multilayer film exhibits good sterilization effect and biocompatibility under the stimulation of bacterial liquid both in vitro and in vivo antibacterial ability tests.

CONCLUSION

Altogether, this study shows that (MMT/PLL-VA)8 multilayer films containing CMS and bacteria-responsive drug release properties posess high bactericidal activity and good biocompatibility. This finding provides a novel strategy for the treatment of bone infections.

Tourniquet-induced ischemia and reperfusion in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone

This study aimed to evaluated ischemic metabolites in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone before, during, and after tourniquet application in a simultaneous paired comparison of tourniquet-exposed and non-tourniquet-exposed legs. Ten patients scheduled for hallux valgus or hallux rigidus surgery were included. Microdialysis catheters were placed to simultaneously and continuously sample the metabolites glucose, lactate, pyruvate, and glycerol bilaterally for 12 h in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone. A tourniquet was applied on the leg planned for surgery (inflation time: 15 min, mean tourniquet duration time (range): 65 (58;77) min). During tourniquet inflation, a 2- to 3-fold increase of the mean lactate/pyruvate ratio was found for all investigated tissues in the tourniquet-exposed leg compared with the non-tourniquet-exposed leg. The lactate/pyruvate ratio recovery time after tourniquet release was within 30 min for skeletal muscle, 60 min for subcutaneous tissue, and 130 min for calcaneal cancellous bone. Only the tourniquet-exposed skeletal muscles were found to be ischemic during tourniquet inflation, defined by a significant increase of the lactate/pyruvate ratio exceeding the ischemic cutoff level of 25; however, this level decreased below 25 immediately after tourniquet release. The glycerol ratio increased instantly after inflation in the tourniquet-exposed leg in skeletal muscle and subcutaneous tissue, and recovered within 60 (skeletal muscle) and 130 min (subcutaneous tissue) after tourniquet release. These findings suggest that applying tourniquet for approximately 1 h results in limited tissue ischemia and cell damage in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone.

Influence of anastomoses on intestine ischemia and cefuroxime concentrations: Evaluated in the ileum and colon in a porcine model

BACKGROUND

Anastomotic leakage is a serious complication following gastrointestinal surgery and is associated with increased morbidity and mortality. The incidence of anastomotic leakage is determined by anatomy and is reported to be between 4%-33% for colon anastomosis and 1%-3% for small intestine anastomosis. The etiology of anastomotic leakage of the intestine has been divided into three main factors: healing disturbances, communication between intra- and extra-luminal compartments, and infection. All three factors interact, and one factor will inevitably lead to the other two factors resulting in tissue ischemia, tissue necrosis, and anastomotic leakage.

AIM

To evaluate ischemic metabolites and cefuroxime concentrations in both anastomosis and non-anastomosis ileum and colon in a porcine model.

METHODS

Eight healthy female pigs (Danish Landrace breed, weight 58-62 kg) were included in this study. Microdialysis catheters were placed for sampling of ischemic metabolites (glucose, lactate, glycerol, and pyruvate) and cefuroxime concentrations in both anastomosis and non-anastomosis ileum and colon. Cefuroxime 1.5 g was administered as an intravenous infusion over 15 min. Subsequently, dialysates and blood samples were collected over 8 h and the ischemic metabolites and cefuroxime concentrations were quantified in all samples. The concentrations of glucose, lactate, glycerol and pyruvate were determined using the CMA 600 Microdialysis Analyzer with Reagent Set A (M Dialysis AB, Sweden), and the concentrations of cefuroxime and meropenem were quantified using a validated ultra-high-performance liquid chromatography assay.

RESULTS

Only the colon anastomosis induced mean ischemic lactate/pyruvate ratios above 25 (ischemic cut-off) throughout the entire sampling interval, and simultaneously decreased glucose concentrations. The mean time for which cefuroxime concentrations were maintained above the clinical breakpoint minimal inhibitory concentration for Escherichia coli (8 µg/mL) ranged between 116-128 min across all the investigated compartments, and was similar between the anastomosis and non-anastomosis ileum and colon. For all pigs and in all the investigated compartments, a cefuroxime concentration of 8 µg/mL was reached within 10 min after administration. When comparing the pharmacokinetic parameters between the anastomosis and non-anastomosis sites for both ileum and colon, only colon T_max and half-life differed between anastomosis and non-anastomosis (P < 0.03). Incomplete tissue penetrations were found in all tissues except for the non-anastomosis colon.

CONCLUSION

Administering 1.5 g cefuroxime 10 min prior to intestine surgery seems sufficient, and effective concentrations are sustained for approximately 2 h. Only colon anastomosis was locally vulnerable to ischemia.

Local concentrations of gentamicin obtained by microdialysis after a controlled application of a GentaColl sponge in a porcine model

Local treatment with gentamicin may be an important tool in the prevention and treatment of surgical site infections in high-risk procedures and patients. The aim of this study was to evaluate the pharmacokinetic profile of gentamicin in bone and surrounding tissue, released from a controlled application of a GentaColl sponge in a porcine model. In eight female pigs, a GentaColl sponge of 10 × 10 cm (1.3 mg gentamicin/cm² ) was placed in a cancellous bone cavity in the proximal tibia. Microdialysis was used for sampling of gentamicin concentrations over 48 hours from the cavity with the implanted GentaColl sponge, cancellous bone parallel to the cavity over and under the epiphyseal plate, cortical bone, the intramedullary canal, subcutaneous tissue, and the joint cavity of the knee. Venous blood samples were obtained as reference. The main finding was a mean peak drug concentration (95% CI) of gentamicin in the cancellous bone cavity containing the implanted GentaColl sponge of 11 315 (9049-13 581) μg/mL, persisting above 1000 μg/mL until approximately 40 hours after application. Moreover, the concentrations were low (<1 μg/mL) in the surrounding tissues as well as in plasma. The mean peak gentamicin concentration from the cancellous bone cavity after a controlled application of a GentaColl sponge was high and may be adequate for the prevention of biofilm formation. However, high MIC strains and uncontrolled application of the GentaColl sponge may jeopardize this conclusion.

Inflammatory proteins in infected bone tissue - An explorative porcine study

Objective

To explore the in situ inflammatory proteins in the local extracellular fluid of infected bone tissue.

Material and methods

Seven pigs went through a two-step surgery performing a traumatically implant-associated Staphylococcus aureus osteomyelitis in the proximal tibia. Five days later, microdialysis catheters (membrane cut off: 20 kDa) were placed in the implant cavity, infected and healthy cancellous bone, and infected and healthy subcutaneous tissue. Plasma samples were collected simultaneously. We employed an antibody-based proximity extension assay (Olink Inflammatory panel) for the measurement of inflammatory molecules within plasma and extracellular fluid of the investigated tissue compartments.

Results

A higher normalized protein expression in the infected bone tissue in comparison to healthy bone tissue was identified for proteins associated with angiogenesis and bone remodeling: OPG, TGFα, MCP-1, VEGFA, and uPA. Moreover, a parallel detectability of the systemic range of cytokines and chemokines as from the investigated local tissue compartments was demonstrated, indicating the same occurrence of proteins in the local environment as within plasma.

Conclusion

An angiogenic and osteogenic inflammatory protein composition within the extracellular fluid of infected bone tissue was described. The findings support the current histopathological knowledge and, therefore, microdialysis may represent a valid method for sampling of material for protein investigation of the in vivo inflammatory composition within the extracellular environment in infected bone tissue.

Single-dose pharmacokinetics of meropenem in porcine cancellous bone determined by microdialysis: An animal study

Objectives

Meropenem may be an important drug in the treatment of open tibial fractures and chronic osteomyelitis. Therefore, the objective of this study was to describe meropenem pharmacokinetics in plasma, subcutaneous adipose tissue (SCT), and cancellous bone using microdialysis in a porcine model.

Methods

Six female pigs were assigned to receive 1000 mg of meropenem intravenously over five minutes. Measurements of meropenem were obtained from plasma, SCT, and cancellous bone for eight hours thereafter. Microdialysis was applied for sampling in solid tissues. The meropenem concentrations were determined using ultra-high-performance liquid chromatography.

Results

The penetration of meropenem into cancellous bone, expressed as the ratio of plasma to cancellous bone area under the concentration-curve from zero to the last measured value, was incomplete and delayed. The time with concentration above the minimal inhibitory concentration (T_>MIC), for an MIC of 0.5 μg/ml, was shorter for cancellous bone in comparison with both plasma and SCT. For MICs above 0.5 μg/ml, T_>MIC in cancellous bone was only shorter than SCT. Considering an MIC of 4 μg/ml, no animals achieved the target of 40% T_>MIC in plasma and cancellous bone, while less than 20% achieved it in SCT.

Conclusion

The main finding of this study was short T_>MIC in cancellous bone after intravenous administration of 1000 mg meropenem. Consequently, in order to achieve sufficient tissue concentration in the cases of open tibial fractures and chronic osteomyelitis, supplemental application of meropenem may be necessary.Cite this article: P. Hanberg, A. Lund, K. Søballe, M. Bue. Single-dose pharmacokinetics of meropenem in porcine cancellous bone determined by microdialysis: An animal study. Bone Joint Res 2019;8:342-348. DOI: 10.1302/2046-3758.87.BJR-2018-0308.R1.

Vancomycin concentrations in the cervical spine after intravenous administration: results from an experimental pig study

Background and purpose - Vancomycin may be an important drug for intravenous perioperative antimicrobial prophylaxis in spine surgery. We assessed single-dose vancomycin intervertebral disc, vertebral cancellous bone, and subcutaneous adipose tissue concentrations using microdialysis in a pig model. Material and methods - 8 female pigs received 1,000 mg of vancomycin intravenously as a single dose over 100 minutes. Microdialysis probes were placed in the C3-C4 intervertebral disc, C3 vertebral cancellous bone, and subcutaneous adipose tissue, and vancomycin concentrations were obtained over 8 hours. Venous blood samples were obtained as reference. Results - Ranging from 0.24 to 0.60, vancomycin tissue penetration, expressed as the ratio of tissue to plasma area under the concentration-time curve from 0 to the last measured value, was incomplete for all compartments. The lowest penetration was found in the intervertebral disc. The time to a mean clinically relevant minimal inhibitory concentration (MIC) of 4 µg/mL was 3, 17, 25, and 156 min for plasma, subcutaneous adipose tissue, vertebral cancellous bone, and the intervertebral disc, respectively. In contrast to the other compartments, a mean MIC of 8 µg/mL was not reached in the intervertebral disc. An approximately 3-times longer elimination rate was observed in the intervertebral disc in comparison with all the other compartments (p < 0.001), and the time to peak drug concentration was higher for all tissues compared with plasma Interpretation - Preoperative administration of 1,000 mg of vancomycin may provide adequate vancomycin tissue concentrations with a considerable delay, though tissue penetration was incomplete. However, in order also to achieve adequate intervertebral disc concentrations in all individuals and accommodating a potentially higher MIC target, supplemental application of vancomycin may be necessary.