Efficacy of five 'sporicidal' surface disinfectants against Clostridioides difficile spores in suspension tests and 4-field tests.

BACKGROUND: A sporicidal surface disinfection is recommended both for the outbreak and the endemic setting but a comparative evaluation on the efficacy of 'sporicidal' surface disinfectants using suspension tests and 4-field tests has not been performed. AIM: To determine the efficacy of five 'sporicidal' surface disinfectants (three ready-to-use wipes (A, B, E), two concentrates (C, D) based on peroxides or aldehydes against C. difficile spores. METHODS: The efficacy was determined under clean conditions using a suspension test and the 4-field test. Each test was performed in duplicate in two separate laboratories. Wipes were wrung to collect the solution for the suspension tests. RESULTS: Product A (peracetic acid; 5 min), product C (peracetic acid; 2% solution in 15 min or 1% solution in 30 min) and product D (peracetic acid; only 2% solution in 15 min) were effective with at least a 4 log10-reduction of C. difficile spores in suspension and on surfaces. Product B (hydrogen peroxide) was not effective in suspension (0.9 log10 after 15 min; 3.2 log10 after 1 h) and on surfaces (2.8 log10 after 15 and 60 min). Product E based on glutaraldehyde, (ethylendioxy)dimethanol and DDAC demonstrated 0.9 log10 after 4 h in suspension and 4.5 log10 after 4 h on surfaces. CONCLUSIONS: Not all surface disinfectants with a sporicidal claim were effective against C. difficile spores in standardized suspension tests and in the 4-field test. In clinical practice preference should be given to products that reliably pass the efficacy criteria of both types of tests.

Interlaboratory reproducibility of a test method following 4-field test methodology to evaluate the susceptibility of Clostridium difficile spores.

BACKGROUND: Sporicidal surface disinfection is recommended to control transmission of Clostridium difficile in healthcare facilities. EN 17126 provides a method to determine the sporicidal activity in suspension and has been approved as a European standard. In addition, a sporicidal surface test has been proposed. AIM: To determine the interlaboratory reproducibility of a test method for evaluating the susceptibility of a C. difficile spore preparation to a biocidal formulation following the 4-field test (EN 16615 methodology). METHODS: Nine laboratories participated. C. difficile NCTC 13366 spores were used. Glutaraldehyde (1% and 6%; 15 min) and peracetic acid (PAA; 0.01% and 0.04%; 15 min) were used to determine the spores' susceptibility in suspension in triplicate. FINDINGS: One-percent glutaraldehyde revealed a mean decimal log10 reduction of 1.03 with variable results in the nine laboratories (0.37-1.49) and a reproducibility of 0.38. The effect of 6% glutaraldehyde was stronger (mean: 2.05; range: 0.96-4.29; reproducibility: 0.86). PAA revealed similar results. An exemplary biocidal formulation based on 5% PAA was used at 0.5% (non-effective concentration) and 4% (effective concentration) to determine the sporicidal efficacy (4-field test) under clean conditions in triplicate with a contact time of 15 min. When used at 0.5% it demonstrated an overall log10 reduction of 2.68 (range: 2.35-3.57) and at 4% of 4.61 (range: 3.82-5.71). The residual contamination on the three primarily uncontaminated test fields was <50 cfu/25 cm2 in one out of nine laboratories (0.5%) and in seven out of nine laboratories (4%). CONCLUSION: The interlaboratory reproducibility seems to be robust.

Efficacy of cleaning tablets for removable orthodontic appliances: an in vivo pilot study.

OBJECTIVES: The purpose of this study was to test the cleaning effect of three commercially available effervescent tablet products on acrylic resin surfaces compared to water as control medium. METHODS: A total of 20 volunteers were instructed to wear a vacuum-formed maxillary splint continuously for 96 h. Each splint incorporated four resin discs in the palate area. Each of these PMMA (polymethyl methacrylate) discs was split into two specimens which were analyzed upon removing the splint after the 4-day period. One specimen per disc was analyzed uncleaned and one after cleaning, using one of the investigated tablet products according to the manufacturer's recommendations or water as control medium. The outcomes of cleaning were evaluated with the modified ortho-phthaldialdehyde (OPA) method by determining the amounts of surface protein. RESULTS: Significant differences in relative (%) protein removal were noted between all three tablet products and water, and fittydent super® was significantly more effective in removing biofilm than Kukis®. No significant differences were observed between fittydent super® and NitrAdine® Ortho&Junior™ or NitrAdine® Ortho&Junior™ and Kukis®. CONCLUSION: The modified OPA method proved to be successful in examining protein-containing contaminations on the specimens, and the effervescent products tested were more effective than pure water in removing contaminants from orthodontic appliances. These results are, however, confined to soft plaque not older than 4 days.

Natural-orifice transluminal endoscopic surgery (NOTES) in Europe: summary of the working group reports of the Euro-NOTES meeting 2010.

The fourth Euro-NOTES workshop took place in September 2010 and focused on enabling intensive scientific dialogue and interaction between participants to discuss the state of the practice and development of natural-orifice transluminal endoscopic surgery (NOTES) in Europe. Five working groups were formed, consisting of participants with varying scientific and medical backgrounds. Each group was assigned to an important topic: the correct strategy for dealing with bacterial contamination and related complications, the question of the ideal entry point and secure closure, interdisciplinary collaboration and indications, robotics and platforms, and matters related to training and education. This review summarizes consensus statements of the working groups to give an overview of what has been achieved so far and what might be relevant for research related to NOTES in the near future.

Comparison of the cleaning and disinfecting efficacy of four washer-disinfectors for flexible endoscopes.

Four washer-disinfectors (AdaptaScope, ETD-2Plus, Innova-E3, LS-2000) were compared. The cleaning and process efficacies of the washer-disinfectors were determined by visible examination and by microbial reduction factor (RF) using the German test method (EN ISO/TS 15883-5). Test pieces were contaminated with blood and Enterococcus faecium. Three cleaners (Cidezyme GI, ETD Cleaner, Liquid 52) and three disinfectants (Cidex OPA-C, ETD Disinfectant, Liquid 44) were used. The cleaning efficacy was also tested with water alone. Effectiveness of Cidezyme GI in the AdaptaScope was determined with an RF of 7.0, in the LS-2000 with an RF of 8.4; Liquid 52 obtained in the LS-2000 an RF of 7.0. The cleaning efficacies with water for the AdaptaScope (RF 2.1) and the LS-2000 (RF 1.2) were significantly different. Microbiological effectiveness of overall processes obtained in the AdaptaScope with Cidezyme GI/Cidex OPA-C (RF 8.4) and in the LS-2000 with Liquid 52/Liquid 44 (RF 9.2) were also significantly different. The test pieces remained contaminated at the end of overall processes in the Innova-E3 and an RF could not be established. In the ETD-2Plus the RFs after the total processes were low (3.7-7.5 and 1.8). The AdaptaScope and LS-2000 consistently produced a microbial reduction, although differences in the efficacy of the overall processes were observed. Processing endoscopes with artificially blocked channels in the AdaptaScope and LS-2000 incurred error messages and the processes stopped whereas the ETD-2Plus and Innova-E3 did not display error messages.

Suitability of the German test method for cleaning efficacy in washer-disinfectors for flexible endoscopes according to prEN ISO 15883.

In Europe, the evaluation of processing flexible endoscopes in washer-disinfectors (WDs) is performed in compliance with prEN ISO 15883-1 which includes determination of the efficacy of the cleaning process. Recent data suggest that cleaning processes show large differences when the prEN ISO 15883-1 German test model is applied. Hence, we analysed a total of 72 experiments in order to evaluate the test method. Transparent test tubes as test pieces (length 2 m, lumen 2 mm) were contaminated with a mixture of blood and Enterococcus faecium. Three set-ups were used: WD 425 with soft water, WD 425 with hard water and WD 440 with demineralized water. WDs were set to perform the cleaning stage of the programme alone. Seven cleaning agents were used according to the manufacturers' instructions (21 cleaning processes); in addition, three cleaning processes were carried out without a cleaning agent (i.e. with water alone). Each cleaning process was assessed by means of three experiments. Suspensions of test organism had 9.2x10(10) colony-forming units (cfu)/mL E. faecium (mean of 24 processes). Controls (recovery) contained 1.0x10(6) cfu/mL E. faecium (mean of 71 experiments). Mean log(10) reduction factors (RFs) for each process, i.e. the difference in microbial loads on the control and the processed tubes, were calculated. Cleaning processes led to RFs of 0-4.1, but no process led to residual bacterial loads below the limit of detection (1.8l gcfu/mL). Standard deviations for a cleaning process were small (< or =0.6 in 79% of the processes) indicating adequate reproducibility. The test model led to reproducible results and revealed large differences between the individual processes. If a cleaning process is intended to result in a bioburden reduction (i.e. RF> or =4), the control must carry a minimum bioburden of 6.5x10(5) cfu/mL. This was achieved in 58% of the processes. However, controls with a bioburden <6.5x10(5) cfu/mL never yielded a residual bacterial load below the limit of detection. We found that the prEN ISO 15883-1 German test method is suitable to determine the cleaning efficacy in WDs and leads to reproducible and valid results.

Intralaboratory reproducibility of the German test method of prEN ISO 15883-1 for determination of the cleaning efficacy of washer-disinfectors for flexible endoscopes.

In Europe, the evaluation of processing flexible endoscopes in washer-disinfectors (WDs) is performed in accordance with prEN ISO 15883-1, which includes determination of cleaning efficacy. Recent data suggest that large differences are found between cleaning processes when the prEN ISO 15883-1 German test model is applied. Therefore, we analysed 12 separate cleaning processes, and each was assessed by determining the means of three experiments. Transparent test tubes used as test pieces (length 2m, lumen 2mm) were contaminated with a mixture of blood and Enterococcus faecium. The WD used was set to perform the cleaning process alone, which consists of three stages (pre-rinse, cleaning, intermediate rinse). Instead of a cleaning agent, demineralized water was used in all three stages of the cleaning process. The mean bacterial load was 10(11.3)cfu/mL (N=12) in the suspensions of test organism, 10(9.1)cfu/mL (N=12) in the test soils and 10(5.8)cfu/mL (N=12) in the controls (recovery). Mean log(10) reduction factors (RF) for each process, i.e. the difference in microbial loads between the control and the processed tubes, were calculated. The 12 cleaning processes with demineralized water led to a mean RF of 2.2 (range: 1.6-3.2) and excellent visible cleanliness of the test pieces. We found that the prEN ISO 15883-1 German test method leads to reproducible and valid results, and is suitable for determining the cleaning efficacy in WDs.

Surface fixation of dried blood by glutaraldehyde and peracetic acid.

The difficulties of successful prion inactivation by chemical agents has led to changes in recommendations regarding the reprocessing of instruments including flexible endoscopes. One of the changes is the preference for peracetic acid instead of glutaraldehyde in order to avoid fixation of organic material, but the surface fixation by various active agents has not been fully investigated. We used a standardized amount of dried blood soil on metal carriers (on average 22 mg). One part of the carriers was exposed to different disinfectants (four based on peracetic acid, three based on glutaraldehyde, two based on quaternary ammonium compounds (QAC), one based on QAC and amines, one based on phenols and one cleaning agent) and air dried. The difference compared with the non-exposed soiled carrier was taken as the measure of blood removal by exposure to the disinfectants. In addition the other part of the carriers was exposed to a cleaning agent and air dried. The cleaning agent itself was capable of removing more than 99% of the dried blood and served as a control for non-fixation. The rate of fixation of dried blood was calculated as the ratio of the weight of residual soil on 'soiled, disinfected and cleaned' carriers and on 'soiled and disinfected' carriers. All experiments were repeated eight times. Blood removal varied between 90.3% +/- 1.5% (phenol-based disinfectant) and < 10% (glutaraldehyde-based preparations). Fixation of the remainder was between 76.9 +/- 8.4% and 102.5 +/- 1.1% with glutaraldehyde and between 19.2% +/- 3.3% and 78.1% +/- 2.4% with peracetic acid. No other preparations showed a potential for blood fixation (< 1.3%). Our findings underline the potential for blood fixation, not only by glutaraldehyde, but also by peracetic acid, and support the evidence that effective cleaning should precede the chemical disinfection.

Efficacy of 10 different cleaning processes in a washer-disinfector for flexible endoscopes.

Successful cleaning of medical devices, such as flexible endocopes, has been recognized to be of major importance for effective processing. Washer-disinfectors (WD) are considered to be an important step in this direction. The cleaning process in WD, however, has only been partially assessed regarding its effectiveness, and therefore to study this in more detail, tests were carried out, according prEN ISO 15883, using transparent teflon tubes as test pieces (length 2 m). For each experiment three test pieces were contaminated with the 'German test soil' containing Enterococcus faecium in blood, two for the test and one as a control (no automatic cleaning). Automatic cleaning was performed with a Wassenburg WD 440. Ten cleaning agents were used. In addition the process was carried out with water alone. After automated cleaning, test pieces were assessed visually (four categories, range: very poor to excellent visible cleanliness) and microbiologically [log(10) reduction factor (RF)]. Each experiment was repeated three times. Using the WD water gave excellent visible cleanliness with a mean RF of 1.1+/-0.6. The same excellent visible cleanliness was obtained with seven cleaning processes: deconex 23 Neutrazym, Helimatic Cleaner enzymatic, Korsolex-Endo-Cleaner, Labomat E, neodisher mediclean, Thermosept ER, and Thermoton NR. Worse visible cleanliness was found with three cleaning processes: Olympus ETD Cleaner and neodisher FE led to adequate visible cleanliness, and the cleaning process with neodisher medizym led to poor visible cleanliness. Six cleaning processes reduced the test organism by RF>or=3, i.e. the reduction was significantly higher than after cleaning with water alone. No significant difference between use of water alone and the cleaning process was found with three cleaning processes: Olympus ETD Cleaner, neodisher mediclean, and Thermosept ER (range RF: 0.8-1.8; P > 0.05). The cleaning process with neodisher medizym yielded a significantly lower mean RF (P = 0.039) in comparison with water treatment alone. Both visible cleanliness and mean RF, varied indicating that the choice of cleaning process had a major impact on the overall result.

The importance of cleaning for the overall results of processing endoscopes.

Reprocessing comprises three steps: cleaning, disinfection and-if required-sterilisation. While the extents of disinfection and of sterilisation are quantitatively defined, there are only imprecise (qualitative) definitions of cleaning. There are two main reasons for accurate cleaning. First organic and inorganic materials that remain on inner and outer surfaces will interfere with the efficacy of the disinfectants. In case of endoscopes this will lead to channel blockages; they remain undisinfected. Second the bioburden found on endoscopes after use can be very high. Data available demonstrate that a bacterial burden of up to 10(9)cfu/endoscope channel can be expected. Therefore it is necessary to perform a thorough cleaning. Studies using endoscopes showed a reduction in microbial counts by a factor of approximately 10(4) by cleaning (manual and mechanical). Therefore in 2001 the German Society of Hospital Hygiene (DGKH) specified its requirements and recommendations for determining cleaning efficacy separately from those for disinfection. Cleaning and disinfecting can be done manually or mechanically, but it seems impossible to validate manual processes. However our studies in two different washer-disinfectors (WD) showed differences in cleaning efficacy. The tested cleaning processes showed different efficacies. Not all cleaning processes showed better results than water alone with regard to visible cleanliness and to a microbiological reduction E. faecium. Our results show that the evaluation of cleanliness exclusively by visible inspection is not sufficient, particular for the lumens of endoscopes. The results also show that a cleaning process may be very effective also in reducing micro-organisms present.

Gastroscope processing in washer-disinfectors at three different temperatures.

Endoscopes are processed chemo-thermally at approximately 56 degrees C in washer-disinfectors in Germany. In this study we investigated the processing of gastroscopes by an endoscope washer-disinfector at different temperatures. A total of 87 gastroscopes were tested hygienically and microbiologically before manual cleaning (after patient use), as well as after manual cleaning and after endoscope washer-disinfector processing at running temperatures of 43, 51 and 56 degrees C. In all tests the suction/biopsy channels of the gastroscopes were flushed with 50 mL sterile solution throughout their full length, from the proximal to the distal ends. The rinse solutions were plated on to various culture media. Also, in order to detect low bacterial counts, 3x10 mL rinse solution was membrane filtrated. The German guideline level for total bacterial counts, applicable since 2002, was exceeded at all temperatures tested (159 cfu/mL at 43 degrees C, <60 cfu/mL at 51 degrees C, and 8 cfu/mL at 56 degrees C). A temperature increase from 43 to 51 degrees C resulted in a highly significant reduction of the residual contamination by aerobic bacteria (P<0.001, Mann-Whitney U Test), Gram-negative bacilli (P<0.001), and pseudomonads (P=0.002). A further temperature increase from 51 to 56 degrees C resulted in a further highly significant drop in residual contamination by aerobic bacteria (P=0.021) and pseudomonads (P=0.036). The aim of the user-minimizing material damage to endoscopes or prolonging their product life-cannot be achieved through lowering the processing temperature without putting patients at risk. In order to ensure adequate processing, endoscope washer-disinfectors should meet the requirements of current draft standards.

Cleaning efficacy of nine different cleaners in a washer-disinfector designed for flexible endoscopes.

Studies on processing endoscopes usually involve the combined cleaning and disinfecting activity. We compared nine cleaning agents designed for automatic processing for cleaning efficacy alone using soft and hard water as controls in 12 different processes in a washer-disinfector. Experiments were performed according to the German Endoscopy Working Group recommendations using transparent Teflon tubes (internal diameter 2mm, length 2m) as test pieces. For each test three pieces contaminated with a blood/test soil containing Enterococcus faecium were used; two for the test and one as a control; each test was repeated three times. Tests were run according to the manufacturer's instructions. Test pieces were assessed visually and microbiologically [log(10) reduction factors (RF) vs. untreated controls]. Soft water alone gave poor visible cleanliness and an RF of 0.3 (SD 0.2), while hard water produced adequate visible cleanliness and an RF of 1.2 (SD 1.0). Five processes gave better visible cleanliness than soft water, but only three were better than hard water. Six processes were worse than soft water and five worse than hard water. Nine processes gave a better microbiological reduction factor than soft water, but the difference was only statistically significant in three. Only one process yielded a significantly higher RF than hard water; three were significantly worse. None of the cleaning processes reached the RF of 4 specified in the US regulations. This study confirms the variability of cleaning processes to dissolve blood residues and reduce the bioburden. We do not recommend abandoning cleaning agents, but suggest that further research is needed to clarify the relationships between washer-disinfectors, cleaning agents, and cleaning performance.

Survival of MRSA on sterile goods packaging.

For many years, MRSA (methicillin-resistant Staphylococcus aureus) has been a world-wide problem. Stringent infection control regimens need to be followed to prevent spread. One such measure is the disposal of unused, MRSA-contaminated single-use items, which is quite expensive. An alternative, less costly measure is to store these items temporarily, re-using them once the organism is non-viable. To establish survival times of MRSA on sterile goods packaging, paper and foil samples were contaminated with MRSA (approximately 10(8)-10(9) cfu/sample). The number of pathogens recoverable from the samples was measured at defined times. MRSA was demonstrated to survive on sterile goods packaging for more than 38 weeks. No MRSA was recoverable after 50 weeks. Temporary storage of MRSA-contaminated single-use items for such a long period of time is not an appropriate or reliable means of decontamination, but many be considered for items that would be costly to replace.

Freely accessible endoscope channels improve efficacy of cleaning.

BACKGROUND AND STUDY AIMS: Inadequate cleaning and disinfection of medical devices, including flexible endoscopes, can result in the transmission of micro-organisms to patients. The aim of this study was to investigate the influence of the design of medical devices on the efficacy of manual cleaning of endoscope channels. MATERIALS AND METHODS: The investigation was carried out using four endoscopes (two duodenoscopes and two gastroscopes). The air/water channels of one duodenoscope and one gastroscope were freely accessible and could be brushed. The instrumentation and the air/water channels were contaminated with blood containing Enterococcus faecium as a test organism. After manual cleaning of the channels by flushing and, where possible, brushing, the recovery rates for the test organism were studied. RESULTS: The comparable rates for recovery of the test organism after cleaning of the instrumentation channels proved that the method used was reproducible. With regard to the air/water channels, the rate of micro-organisms in the cleaning solution recovered after flushing alone was a maximum of 3 % relative to the rate detected after brushing and flushing. CONCLUSIONS: The data collected in the study show that only flushing channels that are not freely accessible resulted in significantly lower (P<0.001) recovery rates for the test organism. In practice, this means that contamination may remain in the channels, and it shows that the design of a medical device has an important influence on the reprocessing of reusable instruments such as flexible endoscopes.

Determination of glutaraldehyde residues on flexible endoscopes after chemothermal treatment in an endoscope washer-disinfector.

BACKGROUND AND STUDY AIMS: Although there are several cases of glutaraldehyde-induced colitis following colonoscopy there is only one study on residues after disinfecting. Our report describes the determination of water-soluble glutaraldehyde residues after processing endoscopes with a glutaraldehyde-containing disinfectant. MATERIALS AND METHODS: A gastroscope and a colonoscope were processed in a washer-disinfector and then immersed in 201 of NaCl solution. Glutaraldehyde was determined by high performance liquid chromatography in 84 samples. Samples were taken after immersing the endoscopes for 5 h and 24 h with and without rinsing the channels. RESULTS: After 5 h and with the channels having been rinsed, the median for colonoscopes was only 0.409 mg/l. The highest level of glutaraldehyde was 0.846 mg/l. CONCLUSIONS: After endoscopes have been processed in the washer-disinfector there is no risk of a glutaraldehyde-induced colitis, proctitis or diarrhoea.

Residuals on medical devices following reprocessing.

Micro-organisms may be transmitted by medical devices. A large variety of infectious agents may be involved in infections transmitted by endoscopic procedures. We review a series of examples that demonstrate to what extent micro-organisms can be detected on medical devices and how transmission on to subsequently examined persons due to inadequate reprocessing can occur. Hardly any data are available regarding residuals of process chemicals, although numerous published cases of glutaraldehyde-related colitis demonstrate that this issue requires urgent clarification. A risk of endoscope contamination exists, interalia, if washer-disinfectors are technically defective or are incorrectly operated. In particular, a final rinse water of poor microbiological quality can lead to recontamination of endoscopes.

Microbicidal activity of a new silver-containing polymer, SPI-ARGENT II.

The survival of three bacterial species and Candida albicans was studied on SPI-ARGENT II. The immediate recovery from silver-impregnated polymer and control polymer (1 cm2) was approximately 10(6) to 10(7) microorganisms. After incubation (37 degreesC) and neutralization of silver with horse serum (5%), surviving organisms were recovered. The survival of the microorganisms on the polymer was not found to be influenced by the silver implantation.

[Fungi and bacteria on air filters from heating, ventilation and air-conditioning systems: a method for determination of fungi and bacteria on air filters]. / Pilze und Bakterien auf Luftfiltern aus Raumlufttechnischen Anlagen: Eine Methode zum Nachweis von Pilzen und Bakterien auf Luftfiltern.

A method was developed for the determination of microorganism concentrations on air filters of HVAC systems, and the influence of different test parameters on the microbiological results was examined by considering various used air filters from several such systems. Microorganisms are detected by shaking air filter samples in fluid, where their concentration is then determined as surface cultures. Since varying the shaking time (30, 60, 90 min) had no influence on the quantitative microorganism determination, a shaking time of 60 minutes was chosen for detection of bacteria, yeasts and moulds. Incubation of blood agar plates either for 4 days at 20 degrees C +/- 2 degrees C or for 2 days at 36 degrees C +/- 1 degree C yielded identical concentrations of bacteria and yeasts. Since results obtained with malt extract agar and Czapek-Dox agar are comparable, one of the two culture media is sufficient for the quantitative determination of moulds on air filters. For statistical evaluation, the inoculation of three parallel agar plates per growth medium was found to be adequate, and the arithmetic mean and the median proved to be equivalent. Investigation on the detection rate showed that, on the average, the method developed demonstrated 80% of the microorganisms detectable on an air filter sample. Thus a simple method is available for quantitative determination of microorganisms on air filters.

The efficacy of low temperature plasma (LTP) sterilization, a new sterilization technique.

The efficacy of low temperature plasma (LTP) sterilization, a newly developed sterilization procedure was tested. Following experiments were carried out: Determination of the most resistant test organism, influence of 10% and 20% defibrinated sheep blood or varying salt concentrations on the efficacy of the sterilization process, influence of the carrier position in the sterilization chamber and in the sterilization pouches, influence of a loaded sterilization chamber, comparative efficacy of EO and LTP, steel carriers with a blood burden of 0%, 5% and 10%, comparative efficacy of EO and LTP, strip carriers in endoscopes, blood burden 0% and 10%, with and without adaptors, evaluation of two bioindicator models. B. pumilus was the test spore that overall seemed to be most resistant to the sterilization procedure. Supplementation of the test suspension with blood or saline crystals resulted in significantly reduced efficacy and has to be avoided in practical operation. The fully loaded sterilization chamber or the position of germ carriers on the shelves had no negative influence on the effectivity of the sterilization process. There were no significant differences between EO and LTP, the blood burden not exceeding 5%. 10% blood burden resulted in a significantly weaker action of LTP. For sterilization of long lumens adaptors containing hydrogen peroxide are necessary. An appropriate bioindicator tube model is introduced.