TECHNIQUE

Production of Antibiotic-Impregnated Beads (Disease Investigation & Management - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords --
Description Choice of antibiotic
  • Amikacin, Gentamicin or Clindamycin can be mixed at 2 g per 20 g PMMA. (J513.2.w1)
  • Neomycin 2.0 g per 20 g plus clindamycin 2.0 g per 20 g has been used (to improve efficacy against gram-negative organisms and anaerobic organisms). (J513.2.w1)
  • Pre-mixed powder containing gentamicin is available. (B600.8.w8)
  • Gentamicin is commonly the antibiotic of choice for PMMA beads in rabbits: it is effective against Pasteurella multocida, withstands the heat generated during curing of the PMMA, and is unlikely to cause antibiotic-associated diarrhoea. (B600.8.w8)

Preparation of beads

  • Make sure all equipment is ready, as the time available once the powdered polymer and liquid monomer have been mixed is limited. 
  • Maintain aseptic conditions throughout preparation. (B600.8.w8, J513.2.w1)
  • Personnel should scrub up before starting preparation. (B600.8.w8)
  • Note that the cement sets in about 15 minutes once mixed, therefore rapid production is important. (B600.8.w8, P3.1999b.w3)
    • Chill the materials, by refrigeration prior to mixing, to prolong setting time. (J513.2.w1, P3.1999b.w3)
  • In the sterile bowl, using a sterile spatula, thoroughly mix the antibiotic powder with the polymethylmethacrylate (PMMA) powder. (B600.8.w8, J29.15.w2, J513.2.w1, P3.1999b.w3)
    • Usually mix 1.0 - 2.0 g antibiotic with 40 - 60 g PMMA powder. (B600.8.w8, J513.2.w1, P3.1999b.w3)
    • A mixture of 1.0 - 2.0 g antibiotic with 20 g PMMA powder has been used. (J513.2.w1, P3.1999b.w3)
    • Maximum of 1:5 antibiotic powder to PMMA powder; the cement will not harden properly if more antibiotic powder is used. (B600.8.w8)
    • If liquid antibiotic is used, the hardness of the final cement is reduced. (B600.8.w8)
  • Add the liquid monomer and mix well to a smooth, even consistency. (J513.2.w1)
    • Normally mix at 2:1 powdered PMMA to liquid monomer; a 3:1 ratio may be preferable since it reaches a temperature of about 65 C maximum compared with 75 C maximum for the 2:1 mix
  • Place the semi-solid mixture into a 20 mL syringe. (J513.2.w1, P3.1999b.w3)
  • Gently expel the mixture onto a sterile surface, in several lines. (J513.2.w1, P3.1999b.w3)
    • Expel the cement fairly quickly for larger diameter beads. (J513.2.w1, P3.1999b.w3)
    • Stretch the line while expelling the cement for smaller diameter beads. (J513.2.w1, P3.1999b.w3)
  • Use a blade to cut the line of cement (still at the malleable stage) into small pieces. (J513.2.w1, P3.1999b.w3)
  • Roll the cement pieces into beads. (J513.2.w1, P3.1999b.w3)

Storing beads

  • Sort the beads by size. (J513.2.w1, P3.1999b.w3)
  • Place the beads in sterile containers. (J513.2.w1, P3.1999b.w3)
  • Label each container with the date of construction of the beads, the type and strength of antibiotic and the expiration date of the antibiotic. (J513.2.w1, P3.1999b.w3)
  • Preferably gas sterilise (ethylene oxide) the beads prior to use. (J513.2.w1, P3.1999b.w3)
    • This may not be needed if strict aseptic technique has been used in production, storage, and removal of beads from their storage container. (P3.1999b.w3)
    • If sterilising with ethylene oxide, leave to aerate for 24 hours prior to use to be sure the gas has dissipated. (B600.8.w8)
    • Note: antibiotic potency may be decreased if beads are autoclaved. (B600.8.w8)

(B600.8.w8, J513.2.w1)

Appropriate Use (?)
  • For prolonged local administration of antibiotic at an infected site (usually area of osteomyelitis) with reduced systemic effects. (P3.1999b.w3)
Notes
  • There is a limited time available once the powdered polymer and liquid monomer have been mixed before the mixture sets. (P3.1999b.w3)
Complications/ Limitations / Risk
  • Care must be taken if antibiotics such as penicillin, ampicillin, amoxycillin, cloxacillin, cephalosporins, clindamicin or flucloxacillin are used. These are suitable for incorporation into PMMA beads but if used in sites where the antibiotic may be ingested (e.g. by the rabbit licking) or reach the oral cavity from the abscess, there is a risk of antibiotic-associated diarrhoea. (B600.8.w8)
  • Chloramphenicol, erythromicin, fusidic acid, polymixin and tetracyclines are not suitable for use in PMMA beads. (B600.8.w8)
Equipment / Chemicals required and Suppliers
  • Sterile bowl

  • Sterile spatula for mixing

  • Sterile gloves

  • Sterile surface

  • Sterile 20 mL syringes

  • Polymethylmethacrylate (PMMA) bone cement polymer plus liquid monomer

  • Sterile antibiotic powder (heat-stable, e.g. amikacin, clindamycin, gentamycin, lincosin, neomycin)

  • Sterile scalpel blade

  • Sterile containers

  • CMW1Gentamicin Bone Cement, DePuy is available as a pre-mixed powder from suppliers of veterinary orthopaedic equipment. (B600.8.w8)

Expertise level / Ease of Use
  • This procedure should only be carried out by an individual with appropriate clinical training and practical experience.
Cost/ Availability
  • Cost depends on the antibiotic chosen.
  • PMMA bone cement polymer plus liquid monomer is widely available.
  • CMW1Gentamicin Bone Cement, DePuy is available as a pre-mixed powder from suppliers of veterinary orthopaedic equipment. (B600.8.w8)
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Frances Harcourt-Brown BVSc FRCVS (V.w140)
References B600.8.w8, J29.15.w2, J513.2.w1, P3.1999b.w3

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