Attenuation of Residual Antibiotics Using Vitamin C in Homograft Heart Valves

Abstract

Objective: The removal of residual antibiotics from whole homograft tissues after disinfection is a matter of concern. To avoid bacteriostasis, which causes falsely negative culture results, we investigated the effectiveness of a novel method applicable to whole homografts.

Methods: Thirty homografts, assessed as unsuitable for transplantation, were obtained from 24 deceased donors. Fourteen days after freezing, each homograft was thawed and divided lengthwise into 2 halves, with one serving as an unexposed control and the other as an exposed sample. Exposure was conducted using 400 µg/mL vitamin C. Five-step microbiological assays were performed using direct tissue samples and cryopreservation solution after thawing. The presence of residual antibiotics in tissue homogenates and cryopreservation solution was assessed by an agar diffusion test on seeded plates with 8 virulent strains. The effect of the intervention was determined by comparing the inhibition zones of exposed and unexposed tissue homogenates.

Results: Blood culture results from all donors were negative. The initial contamination rate was 13.3%, and the isolates were not detected after disinfection. Thawed tissues that were not exposed to vitamin C all yielded negative culture results, whereas one tissue sample exposed to vitamin C had a positive result (Pantoea eucrina). The diameter of the inhibition zone in seeded plates was 14.4% smaller with tissue exposed to vitamin C than that of controls (P=0.021).

Conclusion: The retention of antibiotics and carryover effect are unavoidable. Vitamin C can break down antimicrobial molecules and produce soluble by-products, which leads to a diminished amount of residual antimicrobials and a higher probability of detecting microorganisms in post-disinfection cultures.