title: Novel Antibiotic-loaded Point-of-care Implant Coating Inhibits Biofilm.
abstract: BACKGROUND
  Orthopaedic biomaterials are susceptible to biofilm formation. A novel lipid-based material has been developed that may be loaded with antibiotics and applied as an implant coating at point of care. However, this material has not been evaluated for antibiotic elution, biofilm inhibition, or in vivo efficacy.
  
  
  OBJECTIVE
  (1) Do antibiotic-loaded coatings inhibit biofilm formation? (2) Is the coating effective in preventing biofilm in vivo?
  
  
  METHODS
  Purified phosphatidylcholine was mixed with 25% amikacin or vancomycin or a combination of 12.5% of both. A 7-day elution study for coated titanium and stainless steel coupons was followed by turbidity and zone of inhibition assays against Staphylococcus aureus and Pseudomonas aeruginosa. Coupons were inoculated with bacteria and incubated 24 hours (N = 4 for each test group). Microscopic images of biofilm were obtained. After washing and vortexing, attached bacteria were counted. A mouse biofilm model was modified to include coated and uncoated stainless steel wires inserted into the lumens of catheters inoculated with a mixture of S aureus or P aeruginosa. Colony-forming unit counts (N = 10) and scanning electron microscopy imaging of implants were used to determine antimicrobial activity.
  
  
  RESULTS
  Active antibiotics with colony inhibition effects were eluted for up to 6 days. Antibiotic-loaded coatings inhibited biofilm formation on in vitro coupons (log-fold reductions of 4.3 ± 0.4 in S aureus and 3.1 ± 0 for P aeruginosa in phosphatidylcholine-only coatings, 5.6 ± 0 for S aureus and 3.1 ± 0 for P aeruginosa for combination-loaded coatings, 5.5 ± 0.3 for S aureus in vancomycin-loaded coatings, and 3.1 ± 0 for P aeruginosa for amikacin-loaded coatings (p < 0.001 for all comparisons of antibiotic-loaded coatings against uncoated controls for both bacterial strains, p < 0.001 for comparison of antibiotic-loaded coatings against phosphatidylcholine only for S aureus, p = 0.54 for comparison of vancomycin versus combination coating in S aureus, P = 0.99 for comparison of antibiotic- and unloaded phosphatidylcholine coatings in P aeruginosa). Similarly, antibiotic-loaded coatings reduced attachment of bacteria to wires in vivo (log-fold reduction of 2.54 ± 0; p < 0.001 for S aureus and 0.83 ± 0.3; p = 0.112 for P aeruginosa).
  
  
  CONCLUSIONS
  Coatings deliver active antibiotics locally to inhibit biofilm formation and bacterial growth in vivo. Future evaluations will include orthopaedic preclinical models to confirm therapeutic efficacy.
  
  
  CONCLUSIONS
  Clinical applications of local drug delivery coating could reduce the rate of implant-associated infections.
authors.affiliation: Department of Biomedical Engineering, University of Memphis, 330 Engineering Technical Building, Memphis, TN, 38152-3210, USA, jjnnings@memphis.edu.
authors.forename: Jessica Amber
authors.initials: JA
authors.lastname: Jennings
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Carpenter
authors.forename: Karen S
authors.initials: KS
authors.lastname: Troxel
authors.forename: Karen E
authors.initials: KE
authors.lastname: Beenken
authors.forename: Mark S
authors.initials: MS
authors.lastname: Smeltzer
authors.forename: Harry S
authors.initials: HS
authors.lastname: Courtney
authors.forename: Warren O
authors.initials: WO
authors.lastname: Haggard
mesh_terms: D000583:Amikacin / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects*; D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D051379:Mice; D019095:Point-of-Care Systems; D019736:Prostheses and Implants; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology*; D014640:Vancomycin / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D014640:Vancomycin; D000583:Amikacin