Woodhouse Laboratories

Tag: #sporetest

  • Steam vs Dry Heat vs Chemical Sterilizers – What’s the difference?

    Steam vs Dry Heat vs Chemical Sterilizers – What’s the difference?

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    Instrument sterilization is essential to the functioning of many industries. There are several accepted methods that are used to ensure that instruments are sterilized properly. Below we describe 3 of the most common types of sterilizers used in the medical field.

    Regardless of the type of sterilizer you use, the CDC recommends verifying the proper functioning of your instrument using a weekly spore test. Find out more information at www.WoodhouseLabs.com.

    Steam

    Also referred to as an autoclave, steam sterilizers are the most common popular type of sterilizer, due to their versatility and ease of use. There are two common types of autoclave, gravity displacement or pre-vacuum-type, however both rely on a combination of high temperature, high pressure, and time.

    Sterilization times range from 4-30 minutes depending on the temperature and the load type (wrapped vs unwrapped instruments, liquids vs solids, etc). Most autoclaves include a drying cycle which can last from 25-40 minutes. See your manufacturer’s instructions for exact requirements.

    Common manufacturers of steam sterilizers include: 

    • Midmark
    • Harvey (not including the Harvey Chemiclave)
    • Pelton & Crane
    • Renton
    • Validator (Plus)
    • Ultraclave
    • Statim
    • Magnaclave
    • Kavoklave
    • Tuttnauer
    • Ritter

    Dry Heat

    Dry heat sterilizers are often preferred by clinics exclusively sterilizing metal instruments, as these sterilizers do not require steam which may cause corrosion and dulling of metal equipment. Dry heat sterilizers rely on high temperatures and extended time to destroy microorganisms.

    Sterilization times range from 12-150 minutes, depending on temperature and manufacturer’s instructions.

    Common manufacturers of dry heat sterilizers include:

    • Harvey
    • Dentronix
    • Cox
    • Sterident
    • SteriSURE
    • Wayne

    Chemical/Vapor

    Chemical sterilizers are the least common form of sterilization, due to their cost and potential hazards if handled incorrectly. However, when used properly, chemical sterilizers offer the benefits of both steam sterilizers and dry heat sterilizers – resulting in the reduced wear of metal instruments while requiring a shorter sterilization time. Chemical sterilizers use either Ethylene Oxide (EtO), or a combination of alcohol, formaldehyde, ketone, acetone, and water to create a chemical vapor for sterilizing. Like steam sterilizers, they also rely on a combination of high temperature, high pressure, and time.

    Sterilization times typically range from 20-40 minutes, similar to that of steam sterilizers.

    Common manufacturers of chemical sterilizers include:

    • Harvey (Chemiclave)
    • Vapor Steril

    Need a third party lab to perform your regular spore testing? SporeAlert is a mail-in sterilizer monitoring service that makes it convenient for you to do your routine testing. All you have to do is run the strip through your sterilizer and drop it in the mail. We take care of the rest! For more information click here.

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  • What’s in your spore test? Meet our microbes!

    What’s in your spore test? Meet our microbes!

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    One of the most common questions we get is “What kind of bacteria do you use? Will it make me sick?!” Here we’ve added a brief description of the 2 strains of bacteria that we use for sterilizer monitoring, and some interesting facts on each.

    Geobacillus stearothermophilus

    Geobacillus stearothermophilus was first discovered in 1920, and was originally classified as a member of the genus Bacillus. Until the discovery of archaebacteria in hot springs, G. stearothermophilus was the most heat-resistant organism known to man. It is classified as a thermophile (heat-loving bacterium) and will grow within a temperature range of 30-75 degrees Celsius.

    It has been observed to have to survived temperatures as high as 130 degrees C, making it an ideal specimen for verifying proper sterilization temperatures in steam autoclaves.

    G. stearothermophilus is widely distributed in soil, hot springs, ocean sediment, and is a cause of spoilage in food products. It has not been observed to be pathogenic to any host – which makes it a safe option for sterilizer monitoring! We use G. stearothermophilus to test steam and chemical vapor sterilizers.

    Bacillus atrophaeus

    The majority of Bacillus atrophaeus cultures that we use today are from a lineage of B. atrophaeus that originated at a United States Army Medical Command installation located in Frederick, Maryland in the 1950s.

    The US military used B. atrophaeus as a surrogate for anthrax, as it is non-pathogenic while still being similar to the bacterium Bacillus anthracis for study. The endospores of B. atrophaeus are extremely resistant to stresses, such as chemicals (they can even survive 95% EtOH).

    We use B. atrophaeus to test dry heat and ethylene oxide sterilizers.

    References:

    1. DONK P.J.: A highly resistant thermophilic organism” Journal of Bacteriology 1920; 5, 373-374.
    2. J.E. Thwaite, H.S. Atkins, in Medical Microbiology (Eighteenth Edition), 2012
    3. Nazina, T.N.; Tourova, T.P.; Poltaraus, A.B.; Novikova, E.V.; Grigoryan, A.A.; Ivanova, A.E.; Lysenko, A.M.; Petrunyaka, V.V.; Osipov, G.A.; Belyaev, S.S.; Ivanov, M.V. Taxonomic study of aerobic thermophilic bacilli. Int. J. Syst. Evol. Microbiol. 2001, 51, 433-446.
    4. Gibbons, Henry; et al. (25 Mar 2011). “Genomic signatures of strain selection and enhancement in Bacillus atrophaeus var. globigii, a historical biowarfare simulant”. PLoS ONE. 6 (3): e17836. doi:10.1371/journal.pone.0017836. PMC 3064580 Freely accessible. PMID 21464989.

    Need a third party lab to perform your regular spore testing? SporeAlert is a mail-in sterilizer monitoring service that makes it convenient for you to do your routine testing. All you have to do is run the strip through your sterilizer and drop it in the mail. We take care of the rest! For more information click here.

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