Central Service - Issue 1/2013
- What's New in Standardisation: Draft prEN 285:2013
L. Pineau, E. De Philippe:
Evaluation of endoscope cleanliness after reprocessing: a clinical-use study
The need for manual brushing of endoscope channels before cleaning and disinfecting them in automatic endoscope reprocessors (AERs) is more than ever debated. Most European national guidelines recommend or require manual brushing, while the U.S. Food and Drug Administration (FDA) and the Australian Therapeutic Goods Administration have already accepted claims of high-level disinfection by some AERs without the need for manual brushing when bedside pretreatment is performed.
This study quantitatively assayed total protein, total organic carbon, and viable aerobic bacteria remaining in endoscopes after routine clinical use in order (1) to assess cleanliness after four stages of the usual reprocessing procedure involving AERs and (2) to evaluate the validity of the benchmarks of cleanliness used to validate automatic cleaning claims.
At four different hospitals in France, a total of 206 samples were taken from endoscopes - 87 from colonoscopes, 93 from gastroscopes and duodenoscopes, and 26 from bronchoscopes. 30 were collected after bedside pre-cleaning; 34 after bedside pre-cleaning and channel brushing; 111 after bedside pre-cleaning, channel brushing, and automated washing (after double washing and rinses in the AER); and 31 after bedside pre-cleaning, channel brushing, and the complete washing and disinfection cycle in the AER (full reprocessing). Comparison of samples taken after channel brushing with samples taken before brushing indicated that brushing was important, although not necessarily indispensible, for reducing contamination remaining in endoscopes after bedside pre-cleaning. After the automatic wash phase, residual total organic carbon and bacterial loads were consistent with the limits proposed by Alfa et al. in 2010 and validated by the FDA for an automatic cleaning claim (i. e., < 6.4 µg/cm2 for residual protein and < 4 log10 viable bacteria/cm2) in 91 % and 99 % of cases, respectively. From the 31 endoscopes that were completely reprocessed before sampling, all bacterial counts reached the limits established for automatic cleaning claims. Mean total organic carbon after the complete cycle was one-third the value after the automatic cleaning stage (0.9 µg/cm2 after cleaning and disinfection vs. 2.8 µg/cm2 after only cleaning; not statistically significant). After full processing 23 % of total organic carbon values were lower than the detection limit of the method, in contrast to 67 % for total protein.
Thus, total organic carbon appears to be a more sensitive and reliable measure than total protein measured by Micro BCA™ to accurately measure cleanliness levels. This study demonstrate also that the limits proposed by M. Alfa and validated by FDA and Australia (i. e., < 6.4 µg /cm2 for residual protein and < 4 log10 viable bacteria/cm2) remain valid references for evaluation of reprocessing procedures without manual brushing.
endoscope disinfection contamination reprocessing manual cleaning
Assessment of the biocompatibility of process chemicals used for decontamination of medical instruments
To assess the biocompatibility of residues of process chemicals on the surfaces of reprocessed medical instruments, risk assessment data on the cytotoxic properties, systemic toxicity, irritation and sensitization potential as well as, if applicable, on the haemocompatibility products must be taken into account. In a stepwise test program the cytotoxic characteristics of four products containing detergent and disinfectant substances typically used for decontamination of medical instruments were investigated. The tests revealed that, as expected, disinfectant substances are cytotoxic even in diluted solutions, albeit less intensely so. Other constituents, such as non-ionic surfactants or corrosion inhibitors can also be cytotoxic. The adsorption behaviour evinced by process chemicals when interacting with process challenge devices (PCDs) is a determinant of the cytotoxicity. The stepwise test program performed with diluted solutions and PCDs is suitable for elucidating the cytotoxicity of process chemicals. In combination with the data already available in the majority of cases on the systemic toxicity as well as on the irritation and sensitization potential of the constituent substances, the biocompatibility of process chemicals can thus be evaluated within the framework of risk assessment.
instrument decontamination biocompatibility cleaning disinfection
A. Sava, S. Kritzler:
Protein elimination from medical instruments using alkaline and enzymatic detergents
Recently published data on the transmissibility of Alzheimer's and other protein misfolding diseases further highlights the need to quantitatively remove all proteins from reprocessed medical instruments. To achieve such protein-free instrument surfaces, the CSSD decontamination protocols should be capable of hydrolysing (cleaving) the protein chains into smaller, water soluble fragments.
Alkaline and enzymatic detergents are the only protein hydrolysing options available to healthcare professionals that do not damage medical instruments.
In this paper we have attempted to quantify the protein hydrolysis properties of each class of detergents using SDS-PAGE, stoichiometric calculations, and direct assay of protein hydrolysis in simulated soil. We also present a simple approach to quantify and compare the protein hydrolysing efficacy of various alkaline and enzymatic detergents that would help users to assess the validity of the mostly unregulated «removes protein» claim.
Our results confirmed theoretical knowledge of the vastly superior protein hydrolysis efficacy of proteolytic enzymes over alkaline hydrolysis. Enzymatic detergents with declared proteolytic activities of above 1 Au/L (at in-use dilution) are capable of hydrolysing 100 - 1000 times more peptide bonds than comparable alkaline detergents, making them the preferred choice for instrument reprocessing protocols - whether for prion decontamination or for assured cleaning of medical instruments. Multiple formulation aspects of preserving enzymatic activity whilst maximising the protein hydrolysis rates are discussed. The results alert to a large number of «enzymatic» detergents with virtually non-detectable proteolytic activities (below 0.01 Au/L) present on the market and highlight the need for regulating «removes protein» claims.
prion proteins equipment reuse detergents instrument reprocessing surgical instruments protein folding
Climate change and infectious diseases
Recommendations by the «Quality Task Group»: DGSV Flow Chart 2013 for Classification of Medical Devices