HIGH LOCAL DELIVERY SYSTEMS OF ANTIBIOTICS IN THE TREATMENT OF BIOFILM RELATED INFECTIONS

Gerhard E. Maale, Aniruth Srinivasaraghavan, Daniel K. Mohammadi, Flavio A. Calderon II

The use of local antibiotic delivery systems is common in the management of biofilm-related infections as they provide
high concentrations of local antibiotics while simultaneously avoiding complications from systemic toxicity. Older delivery
mechanisms were associated with a high incidence of wound complications (up to 25%) requiring reoperation. The high
wound complication rate was thought to be due to impurities from the mined calcium sulfate, hydrophobic behavior, and
acidic pH. We are presenting a 100% pure synthetic calcium sulfate hemihydrate (PSCSH) powder mixed with 240 mg liquid
tobramycin and 500 mg of vancomycin powder per 10 cc of the hemihydrate for use in revision surgeries for periprosthetic
joint infections (PJI). The purified carrier demonstrates superior utility to similar vehicles such as poly-methyl-methacrylate
(PMMA) due to the bioabsorbablity which takes 2-3 weeks as demonstrated by disappearance of the hydrated crystal on x-ray.
This is also preferable to the 4-6 weeks bioabsorbablity seen in the mined crystal calcium sulfate variants. The physiological
pH of the PSCSH and the hydrophilicity demonstrated in serum probably account for the low 4% wound complication rate.
The elution of vancomycin and tobramycin was greatest on day 1 compared with those concentrations obtained on days 2,
3, 4, and 5 post-operative while serum concentrations were mostly undetectable. Our findings demonstrate that this PSCSH
preparation provides therapeutic delivery of vancomycin and tobramycin locally at log 2-3 above the minimum inhibitory
concentration (MIC), while avoiding dangerous serum concentrations.