Abstract
The objectives of this study were to report a recipe for making antibiotic impregnated Plaster of Paris (AI-PoP) beads using penicillin, ampicillin, tetracycline, tulathromycin, and florfenicol and to determine the in vitro elution rates of those antibiotics in the beads. The AI-PoP beads were made using Plaster of Paris powder, antibiotic, and water, cured for 24 h, sterilized by ethylene oxide, and stored up to 5 months before testing. For each antibiotic, 20 beads were combined with bovine serum in sterile tubes and incubated at 37°C on a rocker. Serum was replaced at intervals over the 14 days study period, and antibiotic concentrations were determined by high pressure liquid chromatography with mass spectrometry. Separately, in a proof-of-concept study, the growth of E. coli and T. pyogenes in eluent from 10 beads for each antibiotic was quantified by flow cytometry. Antibiotic was detected in AI-PoP bead eluent for 14 days for all but the ampicillin beads, for which antibiotic was detected for 8 days. The concentration of antibiotic in eluent was greater than the minimum inhibitory concentration (MIC) of tested bacteria for the entire study period for penicillin, tetracycline, tulathromycin, and florfenicol. The concentration of ampicillin remained greater than the MIC of E. coli for 4 days and T. pyogenes for 6 days. The colony forming units (CFU)/ml of live E. coli and T. pyogenes was reduced over a 72-h period by 1–3 log10 CFU, with the exception of tetracycline, which reduced CFU/ml of T. pyogenes by <log10 CFU. AI-PoP beads containing penicillin, tetracycline, tulathromycin, and florfenicol elute antibiotic well-above the MIC of selected isolates for the 2 weeks study period. These antibiotics show promise for delivery in joint and wound infections.
Highlights
Synovial sepsis, post-operative surgical site infections, and complicated wounds are a devastating cause of increased morbidity and mortality in large animal veterinary patients and can be career or even life-ending [1,2,3]
All plaster of Paris (PoP) powder used was derived from the same carton, all water was obtained from the same source in the hospital, and all antibiotics were derived from the same bottle or vial
The antibiotic impregnated Plaster of Paris (AI-PoP) beads were allowed to cure in the mold for 24 h at room temperature, sterilized by ethylene oxide, and stored at room temperature
Summary
Post-operative surgical site infections, and complicated wounds are a devastating cause of increased morbidity and mortality in large animal veterinary patients and can be career or even life-ending [1,2,3]. The options for local antimicrobial therapy include intravenous and intraosseous regional limb perfusion [10, 11] and sustained release of antimicrobials eluted from implanted carriers such as collagen sponges [12], polymethylmethacrylate [13, 14], plaster of Paris (PoP) [7,8,9], constant rate infusion systems [15], and hydroxyapatite cement [13]. Plaster of Paris, or calcium sulfate hemihydrate, is inexpensive, readily available, and easy to use for local antimicrobial delivery [15] It is biocompatible, biodegradable, and osteoconductive when used in fracture repair and established osteomyelitis, providing a scaffold on which new bone formation can occur [7, 15]. These studies show that the elution profile is different among antibiotics
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