Assembly of Standardized Test Specimen for Microbial Quantification of Plasma Sterilization Processes of Fine PTFE Tubes as Used in Thermo Sensitive Medical Devices Like Flexible Endoscopes

Abstract

Fine PTFE tubes are used in high‐end and high cost devices like flexible Endoscopes where no standard sterilization procedure like autoclaving applies due to material properties. The study of innovative decontamination processes like plasma sterilization request appropriate analysis methods in order to verify the process functionality. In a related research project the IGB‐cycle‐method for contamination and recovery of indicator organisms like Bacillus atrophaeus spores was developed. It was possible to proof the IGB‐cycle‐method to be reproducible and reliable using round robin tests between three laboratories that compared their results in reference to a relevant level of contamination and recovery. Of a relevant contamination more than 7 log10 steps of cfu/specimen could be recovered from the tube surface.

Innovative Plasma Generation in Flexible Biopsy Channels for Inner‐Tube Decontamination and Medical Applications

“…The proof of microbicidal efficacy of the inner‐tube plasma and the jet‐like plasma was analyzed by means of proliferation assays. The inner tube walls (tube length: 30 cm) were contaminated with Bacillus atrophaeus spores and 0.3% bovine serum albumin (BSA) using a cycle method where a bacteria suspension with an initial concentration of 10 9 CFU · ml −1 (colony forming units per ml) was pumped through the tube for 15 min with a constant flow rate of 15 ml · min −1 14. Prior to the bacteria adhesion cycle method the tubes were also plasma modified, leading to a hydrophilic tube surface (contact angle below 30°) for a better distribution of spores on the surface.…”

“…Here, 50 ml of sterile suspension was pumped through the tube for 20 min at a flow rate of 30 ml · min −1 . With this method the ratio of spores flushed out of the tube to the spores left in the tube is about 10 −4 14. The resulting suspension was diluted in a dilution series and plated on agar afterwards.…”

Multicentre Trials for Decontamination of Fine‐Lumen PTFE Tubes Loaded with Bacterial Endospores by Low and Atmospheric Pressure Plasma

“…The reliability and reproducibility of the used method and workflow for contamination and recovery out of the specimen was shown by previous investigations. Also the independency of the operator of the different methodical steps was proven 12…”

“…According to the previous publication,12 the IGB‐cycle‐method was chosen reliable and reducible enough to assure proper evaluation of the plasma sterilization processes. The reproducible adhesion and distribution of bacterial endospores to the test tubes was achieved using adhesion and drying of the tube.…”

“…The microbial challenge test, usually used for products under development or for validating a production process, does not suit for our investigations. For this reason round robin tests with three laboratories (IGB, INP, HygCen) were conducted 12. The importance of such round robin tests for comparative conclusions have been shown by Köhnlein et al13…”