Validation of “ResEP tube” system for microbiological analysis with removal of antibiotic residues

Abstract: Residual antibiotic concentrations may induce bacteriostasis of microorganisms eventually present on tissue samples and lead to false negative results during microbiological analysis of the sample.
The aim of the study was to validate RESEP for removal of antibiotic residues from solid and liquid samples before microbiological analysis.
The amount of antibiotics in 3-5 ml samples of four bank-prepared antibiotic cocktails, BASE.128 (AL.CHI.MI.A. Srl), cardiovascular, skin, amniotic membrane and corneal tissue samples was determined by HPLC and agar diffusion analyses, before and after treatment with RESEP. Interference of the device with bacterial growth was evaluated performing the microbiological recovery test with inoculants containing 1-10, 10-100 and 100-1000 CFU of European Pharmacopoeia (EP) reference strains (S. Aureus, P. Aeruginosa, C. Albicans, B. Subtilis, A. Niger and C. Sporogenes). Additional tests of the device were performed using different fluids and tissue samples provided by five different tissue banks.
Agar diffusion test and HPLC showed important antibiotic residues in liquid and tissue samples not treated with the RESEP; the amount of antibiotic residues varied depending on the antibiotic cocktail. Complete antibiotic removal from liquid and tissue homogenates decontaminated with BASE.128 was observed after RESEP treatment. Removal of antibiotics from bank-prepared antibiotic cocktails varied from 94-99%.
For EP reference strains, growth was observed for all the tested inoculants.
RESEP treated samples showed significantly higher bacterial recovery as compared to tissues analysed with traditional microbiological methods.
In conclusion, RESEP was validated for the removal of antibiotic residues from both liquid and tissue samples, thus allowing  detection of microbial growth.
The device resulted to be harmless for EP reference strains and showed higher sensibility as compared to currently used microbiological methods in tissue banks.