Antibiotic eluting chitosan glycerophosphate implant in the setting of acute bacterial sinusitis: a rabbit model.

BACKGROUND: Topical therapy offers the potential for treatment of sinonasal disease with minimal systemic side effects. Chitosan glycerophosphate (CGP) is a mucoadhesive polymer that can be used as an antibiotic eluting sinonasal implant in the treatment of sinusitis. The purpose of this study was to assess the potential for CGP as an antibiotic impregnated implant in a rabbit model of acute bacterial sinusitis.

METHODS: The Institutional Animal Care and Use Committee approved study of acute bacterial sinusitis in 12 New Zealand white rabbits using either Pseudomonas aeruginosa (n = 6) or Staphylococcus aureus (n = 6). CGP impregnated with 50 mg of either gentamicin or vancomycin was bilaterally implanted in two rabbits in each arm, respectively. The sinuses were irrigated with saline for 4 days and the lavage was collected for colony-forming unit (CFU) determination. Within each group, the CFU log reduction in the lavage was compared with that of rabbits receiving saline alone (n = 2) or a daily 80-microgram/mL gentamicin or vancomycin irrigation (n = 2) and analyzed using a Student's t-test.

RESULTS: Within the S. aureus group, the CFU log reduction using CGP + vancomycin (-2.57 +/- 0.21) was greater than vancomycin irrigation (-1.66 +/- 0.5; p = NS) and significantly greater than saline alone (2.46 +/- 0.97; p = 0.018). Within the P. aeruginosa group, the CFU log reduction using the CGP + gentamicin (-4.62 +/- 0.74) was greater than gentamicin irrigation (-4.09 +/- 0.70) and saline alone (-1.90 +/- 0.90); however, the results were not significant. In all rabbits receiving the CGP + antibiotic implant, no viable bacteria were present in the lavage by day 4.

CONCLUSION: Placement of a single antibiotic impregnated CGP implant in the setting of an acute Gram-positive or Gram-negative bacterial sinusitis resulted in a greater log reduction of CFU than daily antibiotic irrigation and led to complete sterilization of the lavage within 4 days.