Low-temperature Sterilization Research Articles

Teamwork Achieves High-Quality Medical Devices

Teamwork Achieves High-Quality Medical Devices

過酸化水素/低温プラズマ滅菌法,EOG滅菌法,湿熱処理による蛋白質の構造変化の比較

過酸化水素/低温プラズマ滅菌法,EOG滅菌法,湿熱処理による蛋白質の構造変化の比較

Low-temperature sterilization of wrapped materials using flexible sheet-type dielectric barrier discharge

A flexible sheet-type dielectric barrier discharge (DBD) was studied for the low-temperature sterilization of medical instruments wrapped with Tyvek packaging. Sterilization experiments using Geobacillus stearothermophilus spores with a population of 106 were carried out with various mixtures of nitrogen and oxygen. We confirmed the inactivation of spores after 4.5 min of DBD irradiation at a temperature of 28.4 °C and relative humidity of 64.4%. The main sterilizing factors of this method are the ozone and UV emissions generated by DBD in dry air and synergistic OH radicals generated by DBD in moist air.

Relationship between lumen diameter and length sterilized in the 125L ozone sterilizer

A safe alternative to ethylene oxide for reprocessing heat-sensitive lumen medical devices, such as endoscopes, is needed. The effectiveness of a new, safe, low-cost, and environmentally friendly low-temperature sterilization process using ozone was assessed. Rigid lumen devices were used to assess the maximum length of lumens of different internal diameters that can be sterilized in the TSO(3) model 125L ozone sterilizer. Two inoculation techniques were used. An inoculated wire was placed inside lumens with internal diameters of 0.8 mm and larger, whereas lumens with an internal diameter of 0.5 mm were inoculated directly. Lumens with internal diameters of 0.5 mm, 1 mm, 2 mm, 3 mm, and 4 mm with lengths varying between 45 and 70 cm can be sterilized with ozone. Calculation of the log reduction value for each size demonstrated the achievement of a sterility assurance level of 10(-6). Experimental results demonstrated a linear relationship (with r(2) = 0.990) between the length of lumen that can be sterilized in the 125L ozone sterilizer and its internal diameter. Effective sterilization of an ACMI ureteroscope that is more challenging in terms of sterilant penetration in a small lumen (0.8 mm) compared with the stated lumen claims confirms that the relationship can conservatively be used to predict the length of a lumen device that can be sterilized in the 125L ozone sterilizer for a given diameter. Intermediate sizes of lumen devices that can be sterilized in the 125L ozone sterilizer can be interpolated from the linear relationship between diameter and length found in the present study.

Plasma Sterilisation within Long and Narrow Bore Dielectric Tubes Contaminated with Stacked Bacterial Spores

AbstractCatheters, which comprise small diameter (≤4 mm), long (typically more than a meter), thermosensitive polymer tubings, are generally used only once. This is because conventional low temperature sterilisation techniques are considered inadequate for used catheters. The plasma sterilisation method proposed in the current paper should allow for the achievement of re‐sterilisation of catheters according to accepted regulations. The plasma process described enables one to sterilise, in less than 10 min, the inner part of a long 4 mm i.d. Teflon tube contaminated initially with 106 Bacillus atrophaeus spores. This result was obtained by achieving an argon discharge at reduced pressure (750 mTorr) within the hollow (dielectric) tube itself. The discharge was sustained using a microwave field‐applicator called a stripline, fully enclosing the tube to be treated. This linear field‐applicator yields a uniform plasma all along the tube, hence the uniform biocide action. The biocide agents are the vacuum ultra‐violet (VUV) photons, which include oxygen and nitrogen atomic lines, the N2 Lyman‐Birge‐Hopfield (LBH) bands, the UV photons emitted by the NOβ and NOγ molecular systems resulting from the contamination, even though at a very low‐level, of the argon gas (high purity argon is used) by air. Scanning electron microscopy (SEM) revealed no apparent damage to the external structure of the spores and to polystyrene microspheres exposed to plasma during the time required for reaching sterility.To check for sterility in such narrow bore tubes without having to cut them into two pieces, a procedure was developed to introduce and afterwards collect the bacterial spores used as bio‐indicators. This diagnostic procedure allowed, at the same time, the imaging of the microorganisms relatively efficiently with SEM, showing the eventual stacking of bacterial spores, a possible source of sterilisation failure.magnified image

Prion inactivation using a new gaseous hydrogen peroxide sterilisation process

Prions pose a challenge to decontamination, particularly before the re-use of surgical instruments. They have relatively high resistance to standard decontamination methods and require extreme chemical and/or heat-based treatments for devices used in known or suspected cases of disease. This study investigated the effectiveness of a new gaseous hydrogen peroxide sterilisation process for prions as an alternative low-temperature method. Gaseous peroxide, in addition to known antimicrobial efficacy, was shown to inactivate prions both in in-vitro and in-vivo assays. In contrast to the gas form, liquid peroxide was not effective. The mechanism of action of gaseous peroxide suggested protein unfolding, some protein fragmentation and higher sensitivity to proteolytic digestion. Hydrogen peroxide liquid showed a degree of protein clumping and full resistance to protease degradation. The use of gaseous peroxide in a standard low-temperature sterilisation process may present a useful method for prion inactivation.

Low-temperature sterilization and new technologies

The new low-temperature sterilization technologies are presented as an alternative to the use of ethylene oxide. This review was performed in order to identify evidences of the antimicrobial activity, toxicity, adverse events and the applicability of these technologies. The research was carried through the electronic databases MEDLINE and LILACS up to 2005. The authors analyzed 10 articles in this survey. The studies about the efficacy of these sterilization methods constitute experimental and comparative research that showed the influence of the extension and diameter of the lumen, besides the presence of crystal salts. Thus, choosing the correct equipment is essential, as well as the assurance of the cleansing of the devices, which interfere with the effectiveness of the low-temperature sterilization. These technologies present limitations regarding the sterilization of graft bone and affect the materials properties.

Characteristics of surface-wave plasma with air-simulated N2–O2 gas mixture for low-temperature sterilization

Sterilization experiments using low-pressure air discharge plasma sustained by the 2.45 GHz surface-wave have been carried out. Geobacillus stearothermoplilus spores having a population of 3.0 × 106 were sterilized for only 3 min using air-simulated N2–O2 mixture gas discharge plasma, faster than the cases of pure O2 or pure N2 discharge plasmas. From the SEM analysis of plasma-irradiated spores and optical emission spectroscopy measurements of the plasmas, it has been found that the possible sterilization mechanisms of air-simulated plasma are the chemical etching effect due to the oxygen radicals and UV emission from the N2 molecules and NO radicals in the wavelength range 200–400 nm. Experiment suggested that UV emission in the wavelength range less than 200 nm might not be significant in the sterilization. The UV intensity at 237.0 nm originated from the NO γ system (A 2Σ+ → X 2Π) in N2–O2 plasma as a function of the O2 percentage added to N2–O2 mixture gas has been investigated. It achieved its maximum value when the O2 percentage was roughly 10–20%. This result suggests that air can be used as a discharge gas for sterilization, and indeed we have confirmed a rapid sterilization with the actual air discharge at a sample temperature of less than 65 °C.

Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization

The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 × 106 and 3.0 × 106 were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 °C below that of CW SWPs under the same average microwave power.

Atmospheric pressure resistive barrier cold plasma for biological decontamination

Steady-state atmospheric pressure nonthermal plasmas can splendidly debilitate bacteria in liquids, gases, and on surfaces, as well as can disintegrate hazardous chemicals. The nonthermal resistive barrier gas discharge at atmospheric pressure is currently investigated for low-temperature sterilization purposes. We have carried out electrical, chemical, optical, and biological studies of the discharge, with the intent of identifying the chemically and biologically active species produced. In this paper, we have demonstrated that effective decontamination can be achieved without causing any damage to the active media.

Microscopical Examination: The Impact of Different Ionising Radiation Doses over Protective Clothing Used in the Operating Theatre

The goals to be pursued by this paper are to highlight the effect of different ionising radiation methods, considered low temperature sterilisation, over protective clothing (surgical gowns) used in the operating theatre through microscopical examination. In order to investigate the influence of the radiation on the properties of nonwoven-based surgical gowns, two types of radiation (gamma and electron beam radiation) were considered in this study. The Scanning Electron Microscope (SEM) is widely used in studies of polymers, although for this kind of nonwoven based structures, that goes through sterilisation treatments it isn't commonly used. So, this paper also intends to relate the results of the evaluation of comfort and barrier properties after irradiated at several doses in a range from 0 to 160 kGy.

In vitro cytotoxicity testing of AB‐polymer networks based on oligo(ϵ‐caprolactone) segments after different sterilization techniques

Recently developed versatile biodegradable polymeric biomaterial offer new therapeutic options in numerous medical fields. Biocompatibility is a crucial requirement for the biomedical application of biomaterials, including the sterilization of these materials with the use of accepted protocols. Ethylene-oxide (EO) and low-temperature plasma (LTP) sterilization are frequently used low-temperature sterilization technologies for heat-sensitive materials. The agarose diffusion assay is a recommended cell-screening test to assess the cytotoxicity of biomaterials in vitro. The sensitivity of the agarose assay can be increased by using a modified computer-based image-analysis system. The influence of EO and LTP sterilization on the cytotoxicity of a versatile polymer system of shape-memory polymer networks based on oligo (epsilon-caprolactone) dimethacrylate and n-butyl acrylate was investigated. Statistically significant differences in the rate of cell lysis after EO and LTP sterilization of the polymer samples were detected by using this modified quantification system. The influence of the different sterilization techniques on the cytotoxicity of the polymeric material, as well as the clinical relevance of the described differences, are discussed.

不活性ガスを用いたプラズマソースイオン注入（ＰＳＩＩ）法による滅菌プロセス

Plasma source ion implantation (PSII) with high negative pulsed voltage applied to the workpiece is demonstrated as an effective low-temperature sterilization technique for three-dimensional work pieces. Using an N2 or Ar gas plasma and a pulsed voltage of -5 to -16 kV (10 μs pulse width, 900 pps), the method is shown to reduce the number of active Bacillus Pumilus spores by 3-5 log colony forming units after 15 min exposure.

느타리버섯 봉지재배시 배지 살균 조건에 따른 균사생장 및 자실체 생육 비교

느타리버섯 봉지재배시 살균 온도 및 시간에 따른 배지의 pH와 수분함량 변화, 균사생장 및 자실체 생육 등을 비교한 결과를 보고하고자 한다. 본 시험의 품종은 춘추 느타리 2호와 수한느타리 1호이고 시험배지는 미루나무톱밥 + 폐면 + 비트펄프(40 : 40 : 20%, v/v)와 미루나무톱밥 + 면실피 + 비트펄프(40 : 40 : 20%, v/v)를 사용하였다. 살균 후 배지의 수분함량은 폐면 혼합배지는 저온 살균에서는 1.8% 증가한 반면 면실피 혼합배지는 저온 살균에서 4.1% 감소하였고, 상압 살균과 고압 살균처리는 거의 변화가 없었다. pH는 살균온도가 높을수록 감소량이 많아 저온 살균(<TEX>$60^{\circ}C$</TEX>, 12시간)에서는 거의 변화가 없었으나 상압 살균 (<TEX>$100^{\circ}C$</TEX>, 6시간) 보다 고압 살균 (<TEX>$121^{\circ}C$</TEX>, 90분)에서 감소량이 많았다. 균사배양 및 자실체 생육일수는 저온 살균에서 균사밀도는 가장 낮았으며 배양일수도 가장 길었다. 2주기까지의 수량은 춘추느타리 2호는 폐면 혼합배지의 저온 살균처리에서 가장 낮았으며 그 밖의 처리는 통계적 유의성은 없었고, 생물학적 효율은 면실피 혼합배지를 고압 살균했을 때 96.6%로 가장 높았다. 수한느타리 1호는 면실피 혼합배지의 상압 살균 처리에서 각각 수량 259.1g/pot, 생물학적 효율 94.9%로 가장 높았다. 또한 춘추느타리 2호는 균사 배양 완료 후 배지 경도와 수량과는 고도의 정의 상관관계이며 수한느타리 1호는 배지경도가 지나치게 낮거나 높으면 수량이 감소하는 경향이었다. The suitable sterilization conditions in pot cultivation of varieties of Chunchunutari-2-ho and Suhannutari-1-ho Pleurotus ostreatus were investigated. The substrate formulations for the cultivation consisted of 40% poplar sawdust, 40% waste cotton and 20% beet pulp (PWB), and 40% poplar sawdust, 40% cotton seed hull and 20% beet pulp (PCB). The increase in the sterilization temperature caused decrease in the pH of the substrate. The moisture content of PWB substrate increased by 1.8%, but that of PCB substrate decreased by 4.1 % after low temperature sterilization (<TEX>$12hr\;at\;60^{\circ}C$</TEX>). However, a little change in the sterilization at higher temperature (<TEX>$6hr\;at\;100^{\circ}C\;and\;90min\;at\;121^{\circ}C$</TEX>) did not alter the moisture content of both substrate appreciably. The duration of mycelial growth was longest and its density was lowest in low temperature sterilization (<TEX>$12hr\;at\;60^{\circ}C$</TEX>). The high pressure sterilization (<TEX>$90min\;at\;121^{\circ}C$</TEX>) of PCB substrate produced high yield (236.6 g/pot) and the highest biological efficiency (96.6%) for Chunchunutari-2-ho. On the contrary the high temperatures sterilization (<TEX>$6hr\;at\;100^{\circ}C$</TEX>) of PCB substrate resulted in the yield of 259.1 g/pot with the biological efficiency 94.9% for Suhannutari-2-ho.

Inhibition of Bacillus stearothermophilus Spores in a Liquid Medium by Free Fatty Acids with and without Heat: Possible Mechanisms for the Microbiological Stability of Canned Fat‐Duck Liver

ABSTRACT: :The mechanisms involved in the low‐temperature sterilization of fat‐duck liver (foie gras) are unclear. We have studied the antimicrobial action of its free fatty acids (FFA) on Bacillus stearothermophilus spores in liquid medium. The fat‐liver FFA were identified and assayed, and their action on growth and heat resistance investigated. The major FFA were found to be palmitic, palmitoleic, stearic, linoleic, and oleic acids, the latter (C18:1) being the most abundant. The amount of these FFA in foie gras is much greater than their minimal inhibitory concentrations. They all increased thermal inactivation of B. stearothermophilus spores in our model system and so could contribute to the microbial stability of tinned foie gras.

Fundamentals and applications of late post-discharge processes

Fundamental studies on post-discharges deal with the understanding and the modelling of transport of active species and their interactions with surfaces. Coupling kinetic models of volume and surface processes is a major step in the numerical modelling of surface treatments. Restricted chemical reaction pathways, occurring in post-discharge, are a main advantage in understanding basic phenomena. Efforts to both model and control post-discharge processes have helped to optimise applications of current interest in industry. Nitriding, enhancement of polymer printability, adhesion and wettability properties or remote plasma enhanced chemical vapour deposition of thin films are used for material processing applications. New developments are devoted to surface cleaning and low temperature sterilisation. Versatility of late post-discharge processes may be used for duplex treatments.

A test for cleaning and disinfection processes in a washer-disinfector.

Disinfection processes such as heat, aldehydes or alcohols kill vegetative microorganisms but do not necessarily remove other organic contamination. Organic residues impair the result of low-temperature sterilisation processes. Heat-stable organic residues may give rise to clinical symptoms in the patient. Standards are available in Britain and in Sweden for the examination of cleaning processes in washer-disinfectors. The test substances are artificial soil or blood. These standards are based on visual inspection of instruments or equipment. They cannot be used for examination of tubular instruments, nor can they be quantified. For validation of cleaning procedures a simple quantifiable method, which can be performed in an infection control laboratory is needed. We have used suspensions in horse blood of Enterococcus faecalis bacteria and Bacillus subtilis spores to test disinfection and cleaning in a washer-disinfector. Instruments used for laparoscopic surgery were contaminated with a blood bacteria suspension containing 10(7) organisms/ml and then dried and processed in a washer-disinfector using a regular process. Remaining microbial contamination was cultured quantitatively. Nineteen objects were investigated in 10 experiments each. Cleaning, measured as log reduction >5-6 of B. subtilis, was achieved on surfaces that were adequately in contact with the water flow in the machine. Disinfection (and cleaning) measured as log reduction >5-6 of E. faecalis was successful at all points examined. The test method is simple and quantifiable, and can be used to evaluate and to improve cleaning and disinfection processes.

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone–iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice.

Continuous ethanol production from concentrated wood hydrolysates in an internal membrane-filtration bioreactor.

Continuous culture for the production of ethanol from wood hydrolysate was carried out in an internal membrane-filtration bioreactor. The hydrolysate medium was sterilized at a relatively low temperature of 60 degrees C with the intention of reducing the formation of inhibitory compounds during the sterilization. The maximum ethanol concentration and productivity obtained in this study were 76.9 g/L and 16.9 g/L-h, respectively, which were much higher than those (57.2-67 g/L and 0.3-1.0 g/L-h) obtained in batch cultures using hydrolysate media sterilized at 60 degrees C. The productivity was also found to be much higher than that (6.7 g/L-h) obtained in a continuous cell retention culture using a wood hydrolysate sterilized at 121 degrees C. These results show that the internal membrane-filtration bioreactor in combination with low-temperature sterilization could be very effective for ethanol production from wood hydrolysate.

Infection control: the role of disinfection and sterilization

Many articles that document infections after improper decontamination of patientcare items have emphasized the necessity for appropriate disinfection and sterilization procedures. This paper provides recommendations on the preferred method for disinfection and sterilization of patient-care items based on the intended use of the item (i.e., critical, semicritical, noncritical). The chemical disinfectants recommended for patient-care items and instruments include glutaraldehyde, hydrogen peroxide, peracetic acid, sodium hypochlorite, alcohol, iodophors, phenolics, and quaternary ammonium compounds. The choice of disinfectant, concentration, and exposure time is based on the risk of infection associated with the use of the item. The sterilization methods briefly discussed include steam sterilization, ethylene oxide, new low-temperature sterilization technologies and dry heat. When properly used, these disinfection and sterilization processes can ensure the safe use of invasive and noninvasive medical devices. However, this requires strict adherence to current cleaning, disinfection, and sterilization guidelines.