In vitro evaluation of antibiotic elution from polymethylmethacrylate (PMMA) and mechanical assessment of antibiotic-PMMA composites.
OBJECTIVE
To determine whether different methods of sterilization of antibiotic vials or the heat of polymerization altered the antimicrobial activity or mechanical properties of antibiotic/polymethylmethacrylate (PMMA) composites when compared to antibiotic-free PMMA.


METHODS
In vitro study.


METHODS
Steam-sterilized, gas-sterilized, and non-sterilized 1 gram vials of cefazolin and injectable gentamicin sulfate (high and low doses) were mixed with PMMA to prepare composites for antibiotic elution evaluation, compression, and elongation testing. Blocks of PMMA that contained antibiotic were assayed for antibacterial activity using an agar gel diffusion method or were placed in phosphate buffered saline (PBS) to assess elution of antibiotic. Phosphate buffered saline samples from steam-sterilized cefazolin and high-dose gentamicin groups were assayed on days 1, 2, 5, and 9 for cefazolin or gentamicin concentration by high-pressure liquid chromatography or fluorescent polarization immunoassay, respectively.


RESULTS
PMMA blocks containing antibiotic inhibited bacterial growth of Staphylococcus aureus 25923 for an average of 9 days. Cefazolin and gentamicin concentration in PBS decreased dramatically after the first 24 hours, but remained above minimum inhibitory concentration (MIC) throughout the experiment for all groups except low-dose gentamicin. Compressive strength of plugs made from plain cement and plugs made from PMMA mixed with untreated and steam-sterilized cefazolin was similar, but was significantly different from the other groups. There appeared to be an inverse relationship between compressive strength and elongation.


CONCLUSIONS
PMMA/antibiotic composites inhibited bacterial growth for 7 to 10 days. Compressive strength was affected by different additions of antibiotic.


CONCLUSIONS
Bacteria introduced during a surgical procedure may be inhibited by elution of antibiotic from PMMA at the time of contamination.
Weisman
D L
DL
Department of Veterinary Clinical Sciences, The Ohio State University, Columbus 43210, USA.
Olmstead
M L
ML
Kowalski
J J
JJ
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000662:veterinary; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000737:chemistry / Q000494:pharmacology*; D002437:Cefazolin / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D005839:Gentamicins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D006358:Hot Temperature / Q000009:adverse effects; D008826:Microbial Sensitivity Tests; D019904:Polymethyl Methacrylate / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D013242:Sterilization; D013530:Surgical Wound Infection / Q000517:prevention & control / Q000662:veterinary*
D000900:Anti-Bacterial Agents; D001843:Bone Cements; D005839:Gentamicins; D019904:Polymethyl Methacrylate; D002437:Cefazolin