Low-temperature Sterilization Technologies Research Articles

Does Blood on “Dirty” Instruments Interfere With the Effectiveness of Sterilization Technologies?

Background: Surgical instruments that enter sterile tissue should be sterile because microbial contamination could result in disease transmission. Despite careful surgical instrument reprocessing, surgeons and other healthcare personnel (HCP) describe cases in which surgical instruments have been contaminated with organic material (eg, blood). Although most of these cases are observed before the instrument reaches the patient, in some cases the contaminated instrument contaminates the sterile field, or rarely, the patient. In this study, we evaluated the robustness of sterilization technologies when spores and bacteria mixed with blood were placed on dirty (uncleaned) instruments. Methods: Dirty surgical instruments were inoculated with 1.5105 to 4.1107 spores or vegetative bacteria (MRSA, VRE or Mycobacterium terrae) in the presence or absence of blood. The spores used were most resistant to the sterilization process tested (eg, Geobacillus stearothermophilus for steam and HPGP and Bacillus atrophaeus for ETO). Once the inoculum dried, the instruments were placed in a peel pouch and sterilized by steam sterilization, ethylene oxide (ETO), or hydrogen peroxide gas plasma (HPGP). These experiments are not representative of practice or manufacturer’s recommendations because cleaning must always precede sterilization. Results: Steam sterilization killed all the G. stearothermophilus spores and M. terrae when inoculated onto dirty instruments in the presence or absence of blood (Table 1). ETO failed to inactivate all test spores (B. atrophaeus) when inoculated onto dirty instruments (60% failure) and dirty instruments with blood (90% failure). ETO did kill the vegetative bacteria (MRSA, VRE) under the same 2 test conditions (ie, dirty instruments with and without blood). The failure rates for HPGP for G. stearothermophilus spores and MRSA were 60% and 40%, respectively, when mixed with blood on a dirty instrument. Conclusions:This investigation demonstrated that steam sterilization is the most robust sterilization process and is effective even when instruments were not cleaned and the test organisms (G. stearothermophilus spores and MRSA) were mixed with blood. The low-temperature sterilization technologies tested (ie, ETO, HPGP) failed to inactivate the test spores but ETO did kill the test bacteria (ie, MRSA, VRE). These findings should assist HCP to assess the risk of infection to patients when potentially contaminated surgical instruments enter the sterile field or are unintentionally used on patients during surgery. Our data also demonstrate the importance of thorough cleaning prior to sterilization.Funding: NoneDisclosures: Dr. Rutala was a consultant to ASP (Advanced Sterilization Products)

Comparative Evaluation of the Microbicidal Activity of Low-Temperature Sterilization Technologies to Steam Sterilization

Background: Most medical and surgical devices used in healthcare facilities are made of materials that are sterilized by heat (ie, heat stable), primarily steam sterilization. Low-temperature sterilization methods developed for heat and moisture sensitive devices include ethylene oxide gas (ETO), hydrogen peroxide gas plasma (HPGP), vaporized hydrogen peroxide (VHP), and hydrogen peroxide plus ozone. This study is the first to evaluate the microbicidal activity of the FDA-cleared VHP sterilizer and other methods (Table 1) in the presence of salt and serum (10% FCS). Methods: Brushed stainless steel discs (test carriers) were inoculated with test microbes (Table 1) and subjected to 4 sterilization methods: steam, ETO, VHP and HPGP. Results: Steam sterilization killed all 5 vegetative and 3 spore-forming test organisms in the presence of salt and serum (Table 1). Similarly, the ETO and the HPGP sterilizers inactivated the test organisms with a failure rate of 1.9% for each (ie, 6 of 310 for ETO and 5 of 270 for HPGP). Although steam had no failures compared to both ETO and HPGP, which demonstrated some failures for vegetative bacteria, there was no significant difference comparing the failure rate of steam to either ETO (P > .05) or HPGP (P > .05). However, the VHP system tested failed to inactivate all the test organisms in 76.3% of the tests (206 of 270; P < .00001) (Table 1). Conclusions: This investigation demonstrated that steam sterilization was the most effective method, followed by ETO and HPGP and, lastly, VHP.Funding: NoneDisclosures: Dr. Rutala was a consultant to ASP (Advanced Sterilization Products)

Reply to Randal W. Eveland regarding comparative evaluation of the microbicidal activity of low-temperature sterilization technologies to steam sterilization

Reply to Randal W. Eveland regarding comparative evaluation of the microbicidal activity of low-temperature sterilization technologies to steam sterilization

New developments in disinfection and sterilization.

A review of regulatory clearances for selected new sterilization and disinfection products for the period January 2012-June 2015 indicates continued leverage of established technologies for steam and low-temperature sterilization, and high-level disinfection. New products in these areas were typically modified and improved versions of existing products, with the exception of a new combination hydrogen peroxide/ozone sterilizer. Development of new low-temperature sterilization technologies to address continued evolution of complex medical devices is expected to continue.

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.

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.

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.

Clinical effectiveness of low-temperature sterilization technologies.

The elimination of chlorofluorocarbons by the Clean Air Act has led to the development of alternative technologies for low-temperature sterilization in the healthcare setting, including 100% ethylene oxide, ethylene oxide with other stabilizing gases, immersion in peracetic acid, and gas plasmas. The ideal sterilant does not exist, and infection control professionals should understand the advantages and disadvantages of these processes. However, when combined with adherence to standard cleaning protocols, the available data suggest that the currently available Food and Drug Administration-cleared low-temperature sterilization technologies can inactivate a clinically relevant inoculum of highly resistant organisms.

Clinical Effectiveness of Low-Temperature Sterilization Technologies

The elimination of chlorofluorocarbons by the Clean Air Act has led to the development of alternative technologies for low-temperature sterilization in the healthcare setting, including 100% ethylene oxide, ethylene oxide with other stabilizing gases, immersion in peracetic acid, and gas plasmas. The ideal sterilant does not exist, and infection control professionals should understand the advantages and disadvantages of these processes. However, when combined with adherence to standard cleaning protocols, the available data suggest that the currently available Food and Drug Administration-cleared low-temperature sterilization technologies can inactivate a clinically relevant inoculum of highly resistant organisms.

Comparative evaluation of the sporicidal activity of new low-temperature sterilization technologies: Ethylene oxide, 2 plasma sterilization systems, and liquid peracetic acid

Objective: This study was undertaken to evaluate the efficacy of 4 new low-temperature sterilization technologies: ethylene oxide with hydrochlorofluorocarbons, a liquid peracetic acid immersion system (Steris System 1 Processor), and 2 plasma sterilization processes that use vaporized hydrogen peroxide (Sterrad 100 and the Sterrad 100S). The Sterrad 100S system potentially improves sterilizer efficacy by using 2 cycles of a diffusion stage and a plasma stage per sterilization cycle. Methods: Flat stainless steel carriers were inoculated with approximately 10 6 Bacillus stearothermophilus spores. These carriers were aseptically placed in the middle of 40 cm long stainless steel lumens (hollow tubes). Two types of lumen were used: (1) a lumen test unit with a removable 5 cm center piece (1.2 cm diameter) of stainless steel sealed to the narrower steel tubing by hard rubber septums and (2) a straight lumen. Three different diameters of the lumen test unit (1, 2, and 3 mm) and a single diameter of the straight lumen (3 mm) were studied. At least 40 replicates were performed for each type of lumen and sterilization method. After inoculation, the test unit was evaluated in 1 of the low-temperature sterilization technologies. After sterilization, the carriers were cultured in trypticase soy broth for 14 days at 55°C and assessed for growth of B stearothermophilus spores. Results: Our results demonstrated that ethylene oxide with hydrochlorofluorocarbons, the Sterrad 100S, and the Sterrad 100S half cycle were highly effective in killing approximately 10 6 B stearothermophilus spores present in the center of narrow-lumen stainless steel tubes. As the lumen diameter decreased with the lumen test unit, the Sterrad 100 demonstrated reduced ability to kill B stearothermophilus spores present on the carrier. At the smallest diameter tested (1 mm), the Sterrad 100 system failed 74% of the time. The Steris System 1 was not effective in completely eliminating the 10 6 inoculum under test conditions. Conclusion: The Sterrad 100S was significantly superior to the Sterrad 100 system and equivalent to ethylene oxide with hydrochlorofluorocarbons. Introduction of this new Sterrad 100S system should improve the margin of safety and reduce processing costs by its use of a shorter cycle time. The Steris System 1 is limited by diffusion of the chemical sterilant into the interior of the lumen test unit. (AJIC Am J Infect Control 1998;26: 393-8)

Levels of microbial contamination on surgical instruments

To ascertain the microbial load and type of organisms on used surgical instruments following standard cleaning, which consisted of the use of a washer sterilizer followed by sonic cleaning. In this prospective experimental study, used surgical instruments were immersed in Peptamin Tween broth, the broth agitated, and then filtered through a 0.45 microm filter. Quantitative cultures were performed, and all microbes were identified by using standard techniques. This study was conducted at a 660-bed university hospital. The microbial load remaining on used surgical instruments after cleaning was as follows: 36 (72%) instruments 0 to 10 colony-forming units (CFU), 7 (14%) instruments 11 to 100 CFU, and 7 (14%) instruments > 100 CFU. Organisms contaminating the instruments included coagulase-negative staphylococcus (56%) followed by Bacillus (22%) and diphtheroids (14%). No other microbes were isolated from more than 4% of the instruments. Most used nonlumen surgical instruments contain less than 100 CFU of relatively nonpathogenic microorganisms after cleaning. This suggests that new low-temperature sterilization technologies are likely to be highly effective in preventing cross-transmission of infection via nonlumen medical instruments.

Disinfection and sterilization of patient-care items.

This article 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, dry heat, and the new low-temperature sterilization technologies. 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.

Disinfection and Sterilization of Patient-Care Items

This article 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, dry heat, and the new low-temperature sterilization technologies. 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.