Elution of metronidazole and gentamicin from polymethylmethacrylate beads

Defining the shelf-life of calcium sulfate beads embedded with tobramycin and vancomycin

Background

Antibiotic-laden calcium sulfate beads are gaining popularity in the treatment of orthopaedic infections such as fracture-related infection and osteomyelitis. Calcium sulfate beads have several advantages over polymethylmethacrylate (PMMA) beads as they are bioabsorbable, have demonstrated improved elution characteristics, and have lower peak polymerization temperatures than seen in PMMA. The ability to make and store antibiotic beads for later use has the potential to standardize dosing and decrease operating room times and healthcare costs. This study aims to determine the antibiotic efficacy of premade, antibiotic-laden calcium sulfate beads.

Methods

Calcium sulfate beads containing vancomycin or tobramycin were molded to 4.8 mm in diameter and stored for shelf-life durations of three and six months at 20 °C. A subset of beads was tested immediately after creation. At the designated time points, beads were placed into a buffer solution and incubated at 37 °C with agitation. Antibiotic eluent was collected at 1-hour, 4-hour, 24-hour, and 48-hour timepoints. Eluent concentrations were inferred from a prior study implementing the same calcium sulfate bead model. Eluent was used in microbroth dilution assays to determine its minimum inhibitory concentration (MIC) against methicillin-sensitive Staphylococcus aureus.

Results

MIC assays for tobramycin and vancomycin against S. aureus yielded concentrations consistent with previously reported ranges. MIC results across different bead shelf lives also remained consistent without an increase in MIC with increasing shelf life for either antibiotic.

Conclusions

Shelf life up to six months does not impact the efficacy of tobramycin or vancomycin eluent from calcium sulfate beads in vitro compared to beads made and tested immediately. These results provide preliminary evidence that tobramycin and vancomycin retain their antimicrobial activity in calcium sulfate beads for at least six months stored at room temperature. Additional studies on sterilization techniques are necessary prior to considering use of prefabricated antibiotic-loaded calcium sulfate beads in clinical practice.

Elution profiles of metronidazole from calcium sulfate beads

BACKGROUND

Antibiotic beads are used to treat local bacterial infections by delivering high drug concentrations to infected tissue.

OBJECTIVES

This study examined the elution characteristics of metronidazole from metronidazole-calcium sulfate (MCa) and metronidazole-calcium-potassium sulfate (MCaK) beads over 20 days and the antibacterial efficacy of the beads after storage.

METHODS

The MCa and MCaK beads were prepared by mixing 250 mg of metronidazole and 10 g of calcium sulfate hemihydrate with water and a 3% potassium sulfate solution, respectively. The beads were placed in phosphate-buffered saline for the elution study. The metronidazole eluents were determined using high-performance liquid chromatography. The microstructures were examined by scanning electron microscopy (SEM), and the antimicrobial activity was evaluated by a microbioassay.

RESULTS

For the 20-day study, the total amount of metronidazole released was greater in the MCa beads than in the MCaK beads by 6.61 ± 0.48 mg (89.11% ± 3.04%) and 4.65 ± 0.36 mg (73.11% ± 4.38%), respectively. The amounts of eluted drugs from the MCa and MCaK beads were higher than the minimum inhibitory concentration at 0.5 µg/mL against anaerobic bacteria at both 20 days and 14 days. SEM showed that calcium crystals on the outer surface had dissolved after elution, and thinner calcium crystals were prominent in the MCaK beads. The MCa and MCaK beads exhibited antibacterial activity after setting, followed by storage at room temperature or 4°C for 21 days.

CONCLUSIONS

The MCa beads could release more drug than the MCaK beads, but all eluted metronidazole amounts were effective in controlling bacterial infections. Both metronidazole beads could be stored at ambient temperature or in a refrigerator.

In vitro and in vivo evaluation of gentamicin sulphate-loaded PLGA nanoparticle-based film for the treatment of surgical site infection

The study focuses on the in vitro and in vivo evaluation of the developed gentamicin sulphate (GS)-loaded poly lactic-co-glycolic acid (PLGA) nanoparticle (PNP)-based pullulan film (PNP-F). Sterilization being an essential pre-requisite for the dosage form was carried out using ethylene oxide. Post-sterilization, PNP-F was evaluated for mechanical properties, percentage drug loading, antimicrobial effectiveness study, test for sterility and in vitro dissolution study using Strat-M® membrane. In vitro dissolution study revealed that GS gradually released from PNP-F and the highest cumulative percentage drug release was found to be 86.76 ± 0.03% at 192 h. Wound healing assay was performed to study the effect of PNP-F over migratory potential of dermal fibroblast cells (NIH-3T3) in the presence of micro-organisms, Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). PNP-F inhibited the growth of PA and SA, allowing the growth of fibroblast cells indicating its suitability for application. In vivo study of surgical site was performed by superficial incision model in Wistar rats. Measurement of in vivo incision healing confirmed faster wound healing in the incision which received PNP-F compared to marketed cream containing GS. Graphical abstract.

Effects of Sterilization Techniques on Bioactivity of Polymethyl Methacrylate Antibiotic Beads Containing Vancomycin and Tobramycin

OBJECTIVES

Prefabrication and storage of antibiotic beads may decrease surgical time and allow for use in other settings. This study investigated the effects of sterilization technique and storage time on the bioactivity of antibiotic polymethyl methacrylate (PMMA) beads.

METHODS

Uniform beads of PMMA containing 1 g each of tobramycin and vancomycin were sterilized using autoclave, ethylene oxide (ETO), or ultraviolet (UV) light. Beads were made in a sterile fashion as a control. Disks containing eluted antibiotics from each of the 4 groups were placed onto agar plates inoculated with Staphylococcus aureus. Zones of inhibition, a measure of bioactivity for antibiotic eluted, were determined for the experimental groups and control. Repeat testing was performed for beads stored for 1 week, 1, 3, and 6 months.

RESULTS

Beads sterilized using autoclave, ETO, and UV light showed similar ZOIs after 24 hours of and 1 week of elution compared with the control group. Beads stored for up to 6 months demonstrated similar bioactivity to beads made sterile and tested immediately.

CONCLUSION

PMMA beads containing vancomycin and tobramycin made in a sterile fashion and stored for up to 6 months have the same efficacy as the current standard of beads made sterile and used immediately. The elution and bioactivity of vancomycin-tobramycin antibiotic beads are not negatively impacted by the sterilization methods of autoclaving, ETO gas, or UV light. Furthermore, nonsterile beads can be sterilized and stored up to 6 months with an expected efficacy comparable with beads made in a standard sterile fashion.

Evaluation of vaporized hydrogen peroxide sterilization on the in vitro efficacy of meropenem-impregnated polymethyl methacrylate beads

OBJECTIVE To evaluate the effects of vaporized hydrogen peroxide (VHP) sterilization on the in vitro antimicrobial efficacy of meropenem-impregnated polymethyl methacrylate (M-PMMA) beads. SAMPLE 6-mm-diameter polymethyl methacrylate beads that were or were not impregnated with meropenem. PROCEDURES Meropenem-free polymethyl methacrylate and M-PMMA beads were sterilized by use of an autoclave or VHP or remained unsterilized. To determine the antimicrobial efficacy of each bead-sterilization combination (treatment), Mueller-Hinton agar plates were inoculated with 1 of 6 common equine pathogens, and 1 bead from each treatment was applied to a sixth of each plate. The zone of bacterial inhibition for each treatment was measured after 24 hours. To estimate the duration of antimicrobial elution into a solid or liquid medium, 1 bead from each treatment was transferred every 24 hours to a new Staphylococcus aureus-inoculated agar plate or a tube with PBS solution, and an aliquot of the eluent from each tube was then applied to a paper disc on an S aureus-inoculated agar plate. All agar plates were incubated for 24 hours, and the zone of bacterial inhibition was measured for each treatment. RESULTS In vitro antimicrobial efficacy of M-PMMA beads was retained following VHP sterilization. The duration of antimicrobial elution in solid and liquid media did not differ significantly between unsterilized and VHP-sterilized M-PMMA beads. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that M-PMMA beads retained in vitro antimicrobial activity and eluted the drug for up to 2 weeks after VHP sterilization.

A review of local antibiotic implants and applications to veterinary orthopaedic surgery

In the face of increasing incidence of multidrug resistant implant infections, local antibiotic modalities are receiving increased attention for both infection prophylaxis and treatment. Local antibiotic therapy that achieves very high antibiotic drug concentrations at the site of the implant may represent an avenue for treatment of biofilmforming bacterial pathogens. Randomized controlled trials in human patients have demonstrated an infection risk reduction when antibiotic-impregnated cement is used for infection prophylaxis in implanted joint prostheses, and when a gentamicin-impregnated collagen sponge is used for infection prophylaxis in midline sternotomy. The other modalities discussed have for the most part yet to be evaluated in randomized controlled trials in veterinary or human patients. In general, the in vivo pharmacokinetics and appropriate dosing profiles for local antibiotic modalities have yet to be elucidated. Toxicity is possible, and attention to the dose applied is warranted.

Elution of Clindamycin and Enrofloxacin From Calcium Sulfate Hemihydrate Beads In Vitro

OBJECTIVE

To compare the in vitro elution characteristics of clindamycin and enrofloxacin from calcium sulfate hemihydrate beads containing a single antibiotic, both antibiotics, and each antibiotic incubated in the same eluent well.

STUDY DESIGN

Experimental in vitro study.

METHODS

Calcium sulfate hemihydrate beads were formed by mixing with clindamycin and/or enrofloxacin to create 4 study groups: (1) 160 mg clindamycin/10 beads; (2) 160 mg enrofloxacin/10 beads; (3) 160 mg clindamycin + 160 mg enrofloxacin/10 beads; and (4) 160 mg clindamycin/5 beads and 160 mg enrofloxacin/5 beads. Chains of beads were formed in triplicate and placed in 5 mL phosphate buffered saline (PBS; pH 7.4 and room temperature) with constant agitation. Antibiotic-conditioned PBS was sampled at 14 time points from 1 hour to 30 days. Clindamycin and enrofloxacin concentrations in PBS were determined using high-performance liquid chromatography.

RESULTS

Eluent concentrations from clindamycin-impregnated beads failed to remain sufficiently above minimum inhibitory concentration (MIC) for common infecting bacteria over the study period. Enrofloxacin eluent concentrations remained sufficiently above MIC for common wound pathogens of dogs and cats and demonstrated an atypical biphasic release pattern. No significant differences in elution occurred as a result of copolymerization of the antibiotics into a single bead or from individual beads co-eluting in the same eluent well.

CONCLUSION

Clindamycin-impregnated beads cannot be recommended for treatment of infection at the studied doses; however, use of enrofloxacin-impregnated beads may be justified when susceptible bacteria are cultured.

Sterilization by gamma radiation of antibiotic impregnated polymethylmethacrylate and plaster of Paris beads. A pilot study

INTRODUCTION

Ethylene oxide is currently recommended for sterilization of antibiotic impregnated beads; however this method carries health risks to personnel and is becoming less available.

OBJECTIVE

To perform a pilot study of the effect of radiation for sterilization of polymethylmethacrylate (PMMA) and plaster of Paris (POP) beads impregnated with amikacin, enrofloxacin, and ceftiofur.

HYPOTHESIS

Radiation would effectively sterilize the beads without affecting the efficacy of the antibiotic.

MATERIALS AND METHODS

Beads of PMMA and POP were prepared in a clean but non-sterile manner with one of the three antibiotics (amikacin, enrofloxacin, ceftiofur) or no antibiotic. Beads were then exposed to radiation for a total dose of 0 kiloGray (kGy), 10 kGy and 25 kGy. Beads were incubated on Mueller-Hinton agar plates seeded with Escherichia coli, Staphylococcus aureus or Pseudomonas aeruginosa for 24 hours or cultured in brain-heart infusion broth for 48 hours. Zones of inhibition were measured on the agar plates and statistics were performed on the diameters of the zones of inhibition using an analysis of variance.

RESULTS

There were no differences in the diameters of inhibition for all levels of radiation for all PMMA beads. The same was true with POP beads with the exception of enrofloxacin which had a significantly decreased zone of inhibition with increased levels of radiation, though the clinical significance of this finding was not assessed. Only beads without antibiotics and not exposed to radiation had bacterial growth.

CLINICAL SIGNIFICANCE

Radiation may be an effective method of sterilization for antibiotic impregnated beads.

In vitro elution of amikacin and ticarcillin from a resorbable, self-setting, fiber reinforced calcium phosphate cement

OBJECTIVE

To determine in vitro elution characteristics of amikacin and ticarcillin from fiber reinforced calcium phosphate beads (FRCP).

SAMPLE POPULATION

Experimental.

METHODS

FRCP beads with water (A), amikacin (B), ticarcillin/clavulanate (C), or both amikacin and ticarcillin/clavulanate (D) were bathed in mL phosphate-buffered saline (PBS) at 37°C, 5% CO(2) and 95% room air. PBS was sampled (eluent) and beads were placed in fresh PBS at time points 1 and 8 hours and 1, 2, 3, 4, 5, 6, 7, 10, 12, 14, 18, 21, 25, 28, 35, 42, 49, and 56 days. Antibiotic concentration and antimicrobial activity of eluent against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae were determined.

RESULTS

Both antibiotics eluted in a bimodal pattern. Beads with a single antibiotic eluted 20.8 ± 2.5% of amikacin and 29.5 ± 0.8% of ticarcillin over 56 days. Coelution of the antibiotics resulted in a lower proportion (AUC(0-∞) ) of antibiotics eluted for both amikacin (9.5 ± 0.2%) and ticarcillin (21.7 ± 0.09%). Bioassay of antimicrobial activity of the eluent (t = 1, 8, and 24 hours) established reduced antimicrobial activity of amikacin from combination beads (D).

CONCLUSIONS

FRCP beads with amikacin or ticarcillin/clavulanate, but not the combination, are suitable carriers for wound implantation.

CLINICAL RELEVANCE

Duration before complete resorption of FRCP beads in vivo should be determined before clinical use as a resorbable depot. The results of this study underscore the importance of testing drug combinations, despite success of the combination systemically, before their use in local applications.

Foreign body urethral obstruction in a chimpanzee (Pan troglodytes)

BACKGROUND

A 34-year-old, captive-born, vasectomized male chimpanzee (Pan troglodytes) presented with lethargy and scrotal swelling.

METHODS

Urethral obstruction was diagnosed via urethroscopy.

RESULTS

Removal of the grass stem foreign body resolved the obstruction. Scrotal and preputial ulceration developed from urine scald, which was managed with surgical debridement and antibiotics.

CONCLUSIONS

After 7 weeks, the animal was reintroduced to its troup and has been healthy for 11 months.

Assessment of antimicrobial microspheres as a prospective novel treatment targeted towards the repair of perianal fistulae

BACKGROUND

None of the proposed materials tested for the management of perianal fistulae has proven to be a definitive treatment.

AIM

To assess a new repair scaffold and drug delivery device conceived to target perianal fistula repair.

METHODS

Poly(D,L-lactide-co-glycolide) porous microspheres containing either antibacterial silver-releasing degradable phosphate glass or metronidazole were prepared using thermally induced phase separation.

RESULTS

Ion- and drug-release profiling of the microspheres revealed continued release of silver ions from microspheres filled with silver-doped phosphate glass and high encapsulation efficiency for metronidazole [78% and 82% for microspheres loaded with 2.5% and 1.3% (w/w), respectively]. Microbicidal activity was confirmed by growth inhibition of bacterial species (Staphylococcus aureus, Escherichia coli and Bacteroides fragilis), which characteristically dominate the colonization of perianal fistula tracts. Microspheres containing >3 mol% silver or metronidazole resulted in strong bacterial inhibition/kill against B. fragilis; the presence of one sphere containing >3 mol% silver had a potent inhibitory effect against all the microbes studied. Microspheres became rapidly integrated with host tissue following subcutaneous implantation into a rodent wound model.

CONCLUSION

The study demonstrates a novel scaffold for guided tissue regeneration providing local release of antimicrobial agents sufficient to counter bacterial colonization and warrants further investigation.

In vitro elution studies of amikacin and cefazolin from polymethylmethacrylate

OBJECTIVE

To compare the in vitro elution characteristics of amikacin and cefazolin from polymethylmethacrylate (PMMA) alone and in combination.

STUDY DESIGN

A prospective, controlled, experimental study.

METHODS

Three aliquots of 6 g sterile PMMA were measured and to them added (1) 750 mg amikacin; (2) 1050 mg cefazolin; and (3) 750 mg amikacin and 1050 mg cefazolin. Ten beads of each antimicrobial/PMMA combination were placed in 5 mL phosphate-buffered saline (PBS) at pH 7.4 and room temperature with constant agitation. PBS was sampled at 15 time points between 1 hour and 30 days. Amikacin concentrations were determined by fluorescence polarization immunoassay and cefazolin concentrations by high-performance liquid chromatography.

RESULTS

Amikacin and cefazolin eluted at concentrations greater than 8 and 4 times, respectively, above the minimum inhibitory concentration (MIC) for susceptible bacteria over 30 days. Co-elution of the antibiotics resulted in a greater rate and proportion of antibiotic eluted. Concentrations of amikacin and cefazolin in the co-eluted fluid were not maintained sufficiently above the MIC for selected bacteria over 30 days.

CONCLUSIONS

PMMA beads of only amikacin or cefazolin-eluted concentrations greater than the MIC for selected bacteria for 30 days. Co-elution of the antibiotics at the selected doses resulted in a significantly shorter duration of elution and may not be effective for treatment of wound infection.

CLINICAL RELEVANCE

Co-elution of amikacin and cefazolin from PMMA at the selected doses cannot be recommended for sustained treatment of infection.

Septic Arthritis, Tenosynovitis, and Infections of Hoof Structures

Infectious diseases of synovial and hoof structures in horses can be devastating to soundness and can result in life-threatening complications. Timely diagnosis and early aggressive treatment can result in successful outcomes and resumption of athletic careers; however, delays in recognition and therapy can be the most costly reasons for failure. Sterilization of affected compartments and tissues requires removal of microorganisms and compromised tissue. Debridement, lavage, and appropriate antimicrobial drug use are the most reliable avenues of treatment. Antimicrobial drugs can be administered by local, regional, and systemic routes. Lavage techniques and debridement typically require surgical manipulations.

Comparative Study of Antibiotic-Containing Polymethylmetacrylate Capsules and Beads

BACKGROUND

This study aimed at making local antibiotic therapy wider in cases of chronic suppurations by administering antibiotics which previously could not be given in this way through the conventional polymethylmetacrylate (PMMA) carrier techniques. Capsules from this material were produced with a pressing machine designed and laid out by us. The characteristics of antibiotic penetration from this novel carrier were compared to those of PMMA beads.

METHODS

The time-dependent outflow of amikacin, clindamycin, pefloxacin, piperacillin + tazobactam, amoxicillin + clavulanic acid and cefotaxime was examined from the capsules and the beads with standard microbiological techniques using the Micrococcus luteus ATCC9341 test strain. The diameter of the inhibitory zones was measured after 24 h incubation at 37 degrees C and converted to mug/ml antibiotic concentrations.

RESULTS AND CONCLUSIONS

Our results revealed that all antibiotics showed longer-lasting and higher concentration outflow from the PMMA capsules than from the beads. Therefore, these capsules can provide a more promising new opportunity for specific local antimicrobial treatment in cases of chronic suppurative bone and soft tissue injuries. In these cases the polymerization has already been completed and the heat does not influence the structure of the antibiotics; therefore, it can be inserted into the capsules in powder or solution form.