Pressure cooker autoclave

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Posted by gerryshown00 from the Computers category at 20 Aug 2022 05:15:34 pm.
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Laboratory science requires careful maintenance of sterile reagents and tools as well as the sterilization of waste prior to disposal. However, steam autoclaves typically used for this purpose may not be readily accessible to everyone in the scientific community, such as K-12 teachers, researchers in the field, students in under-funded laboratories, or persons in the developing world who lack funding and resources. This work examines the use of commercial electric pressure cookers as an alternative method for the sterilization of media, instruments, and waste. Four commonly available brands of pressure cooker were tested for their ability to sterilize microbiological media, a variety of metal instruments, and high-titer microbial cultures. All four pressure cookers were able to sterilize these starting materials as well as a range of microbial types, including Gram-positive bacteria, Gram-negative bacteria, filamentous fungi, unicellular fungi, and mixed environmental samples. Only the Instant Pot, however, was able to sterilize autoclave tester ampoules of Geobacillus stearothermophilus spores. These results suggest that, depending on the nature of the work undertaken, store-bought pressure cookers can be an appropriate substitute for commercial autoclaves. Their adoption may also help increase the accessibility of science to a broader range of investigators.

Laboratory research, medical treatment, industrial production of pharmaceuticals, and a wide variety of other scientific applications all rely on sterilization procedures to protect workers and consumers from pathogenic contaminants. This may manifest as the maintenance of axenic strains for study and storage, the preparation of surgical devices, the growth of large cultures for compound extraction and purification, among others. Even space exploration labs work to sterilize equipment that will land on other planets to prohibit the introduction of Earth microbes capable of colonization and, possibly, destruction. A strict definition of sterilization requires every organism to be inactivated following a sterilization procedure . A more realistic definition of sterility stipulates that, if sterile, no growth will be observed upon incubation in appropriate growth medium. This second definition is likely more accurate when considering the level of sterility achieved in most laboratory or medical situations because it may not be possible to verify that every contaminant is inactivated, but observing outgrowth, or lack thereof, is usually possible. To this end, the World Health Organization, U.S. Pharmacopeia, International Organization for Standardization, U.S. Food and Drug Administration, and others have set forth standards that must be met to consider a surface or item sterile for human use.

Various methods are available to sterilize equipment and surfaces, including ethylene oxide gas, compounds like phenol, glutaraldehyde, peracetic acid, and hydrogen peroxide, dry heat, UV irradiation, and steam sterilization [2]. Steam sterilization is usually conducted in an autoclave that reaches and maintains 121°C and 15 PSI for a desired duration, often at least 30 min. In other cases, however, longer sterilization times at temperatures as low as 115°C are considered appropriate to inactivate contaminants. The use of autoclaves as sterilization devices is ubiquitous across laboratories and medical facilities because of the short time required for sterilization, the ease of training and use of the equipment, the absence of harmful chemicals, and the consistent reproducibility as a means of pathogen control [3]. To verify that an autoclave is consistently reaching the desired temperature and pressure for sterilization, biological tests are regularly conducted to demonstrate that the most heat-resistant organisms are inactivated, which implies that all other more sensitive contaminants would be similarly sterilized [4]. In one of the more common tests, a suspension of especially heat-resistant Geobacillus stearothermophilus (originally deposited as Bacillus stearothermophilus Donk) endospores is autoclaved and growth is assessed either by plate-based growth or by the appearance of turbidity and color change of an indicator dye [5, 6]. Failure of the endospores to germinate and grow indicates that the autoclave is functioning properly.

Failure to achieve sterile materials, especially those that are to be re-used (such as surgical instruments, tools like bronchoscopes, and autografts in medicine and culture glassware in laboratories) may result from many user- and machine-oriented causes. A serious example of user error in sterilization was described by Dancer et al; an outbreak of surgical site infections in orthopaedic patients and endophthalmitis in ophthalmology patients occurred in sequence despite having relatively little overlap in specialty surgical instruments used by the two departments [7]. Much more common causes of equipment sterilization failure are due to flaws in the machine itself, as evidenced by reports of primary inoculation tuberculosis after contaminated acupuncture needles were used, a Pseudomonas aeruginosa outbreak after steam sterilization inadequately removed residual material from arthroscopic tools, a Mycobacterium chelonae outbreak after laparoscopic instruments were chemically disinfected but subsequently rinsed in trays containing a M. chelonae biofilm, and a similar outbreak of M. chelonae in a private plastic surgery clinic after liposuction tubing was colonized with a biofilm [8–11]. Though these published accounts highlight sterilization mishaps in medicine, equally common are those that occur in the lab, however, they are rarely published because the consequences are relatively minor. These incidents of contamination leading to pathology illustrate the need for sterilization and verification of the means of achieving it.

While steam sterilization is a common means of decontaminating instruments and surfaces, autoclaves can be prohibitively expensive for underfunded research and teaching facilities. Additionally, the cumbersome size and weight of both floor and benchtop autoclaves hinders their transportation to field sites. To provide a possible sterilization alternative to large pricey autoclaves, we assessed the viability of using electric, self-contained pressure cookers to sterilize laboratory instruments and media and inactivate high titers of various microbes. Of the four brands of 8-quart pressure cookers tested, all were able to inactivate contaminants in media, consumables, and fungal and bacterial cultures within a maximum of 60 mins of run time. In this work, run time is the time spent at the operating temperature and pressure of the pressure cooker likely resulting in sterilization. Only the Instant Pot brand pressure cooker was able to inactivate G. stearothermophilus endospores, which indicated that it would be the most appropriate choice for a laboratory pressure cooker. These results suggest that pressure cookers can sterilize laboratory components sufficiently for use in a relatively short timeframe, which may make sterilization available to many more groups worldwide.
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