Abstract: Decontamination of tissue allografts in antibiotic cocktails can lead to the antibiotic carry-over effect, which in turn can result in the false negative microbiological analysis and in uncontrolled introduction of antibiotics in receiving patient.
Purpose: Elimination of the antibiotics carry-over through neutralization with resin mixture, designed specifically for elimination of antibiotics from tissues previously decontaminated with the industrially manufactured medical device BASE.128.
Methods: Sterile Amberlite resins (XAD16, XAD18, XAD4, PFC3500, CG50) and C18 resins were tested. Porcine heart valve, bone and skin segments were decontaminated at 37°C for 6h and at 4°C for 24h with BASE.128 containing Vancomycin, Gentamicin, Amphotericin B and Cefotaxim. Tissue samples were then incubated for 1h at room temperature under continuous stirring in presence of resin mixture. Removal of antibiotics from the broth and tissue homogenate was assessed by agar diffusion test. 10-100 cfu/ml of Pharmacopea reference microorganisms S. Aureus (SA), C. Albicans(CA), P. Aeruginosa (PA), and an additional bacterial strain: methicillin-resistant S. Epidermidis (SEMR) were used to test the compatibility of resins with microbial survival. Adhesion of microorganisms was evaluated by plating the medium on a Petri dish and quantifying bacteria before and after neutralization with different resins.
Results: Tissue samples introduced into the growth broth immediately after decontamination and without rinsing induced inhibition of bacterial growth of some tested microorganisms. One of the tested mixtures of non ionic hydrophobic adsorbent resins and exchange resins contrasted efficiently such carryover effect. The absence of inhibition areas in the agar diffusion test demonstrated the antibiotic removal from decontaminated tissue samples. The efficiency of the antibiotic removal from the tissue samples depended on antibiotic, time of contact between resin and antibiotic solution, quantity of resins and tissue. No interference with bacterial survival was present for all resins. However, the investigated ion exchange resins showed a small bacteriostatic effect against SA, SEM, PA but not CA.
Conclusions: Our study permitted to design an antibiotic-neutralizing mixture compatible with bacterial survival and proliferation. Neutralizing resins added directly in growth medium eliminated efficiently antibiotic carryover effect induced by not rinsed decontaminated tissues samples.