Discussion

Sterilization technologies are essential for instrument reprocessing in healthcare facilities. Cleaning, or the removal of visible soil (eg, organic and inorganic material) and microbial contaminants from objects and surfaces, precedes sterilization. Cleaning should consistently and reliably remove and/or reduce the organic and inorganic materials before sterilization to not interfere with the effectiveness of sterilization and to ensure a sterility assurance level of 10^{−Reference Alfred, Catchpole, Huffer, Fredendall and Taaffe6} . ^{Reference Rutala and Weber1} The criticality of cleaning was reconfirmed by Alfa et al ^{Reference Alfa, DeGagne, Olson and Puchalski2} in a classic study that evaluated various low-temperature sterilization technologies and showed sterilization failure in the presence of salt, serum, and lumen test units. Given that organic material and salts are known to influence the sterilization capacity of low-temperature sterilization technologies, ^{Reference Rutala and Weber1–Reference Diab-Elschahawi, Blacky, Bachhofner and Koller5} we evaluated the impact of inadequate cleaning and blood on the efficacy of the sterilization technologies used in the United States.

The frequency of instrument contamination in the operating room is poorly described in the literature. When instruments are contaminated with organic material from a prior procedure, healthcare personnel refer to that as “bioburden.” One study found contamination problems in the operating room in ˜1% of surgical instruments, and ˜50% of the contamination type reported by the operating room staff was bioburden (ie, organic material such as blood or tissue), which was categorized differently than foreign bodies in the tray (eg, hair or object). ^{Reference Alfred, Catchpole, Huffer, Fredendall and Taaffe6} Rarely do these instruments with bioburden touch the patient; however, there is a potential for contaminating the surgical field. In this study, we assessed this instrument contamination issue and the cliché, “If it’s not clean, it’s not sterile.”

Our results showed that steam sterilization is the most robust (ie, has the greatest ability to withstand and overcome adverse conditions or rigorous testing) sterilization process. It was effective even when instruments were not cleaned (“dirty” instruments) and the test organisms (G. stearothermophilus spores, M. terrae) were mixed or overlaid with blood. Low-temperature sterilization technologies tested failed to inactivate the test spores (ie, B. atrophaeus for ETO and G. stearothermophilus for HPGP) on “dirty” instruments with or without blood. ETO did kill the vegetative test bacteria (ie, MRSA and VRE), but HPGP did not kill P. aeruginosa, MRSA, or VRE on “dirty” instruments with or without blood.

These results demonstrated that some sterilization technologies were more “forgiving” or safe when cleaning is incomplete. The robustness of some sterilization technology, such as steam sterilization, makes it exceedingly unlikely that a steam-sterilized instrument will be the source of infection. These findings should assist healthcare personnel in assessing the risk of infection to patients when potentially contaminated surgical instruments enter the sterile field or are unintentionally used on patients during surgery.

The findings regarding the robustness of steam sterilization should not be used to suggest that cleaning is unimportant for steam sterilization. In contrast, the data demonstrate how important cleaning is prior to sterilization because salt and organic matter left on instruments can interfere with low-temperature sterilization. These results, and those of other investigations, ^{Reference Alfa, DeGagne, Olson and Puchalski2–Reference Diab-Elschahawi, Blacky, Bachhofner and Koller5} highlight the importance of real-time monitoring methods prior to sterilization that are reliable, validated, and assess the effectiveness of cleaning that is predictive of microbial contamination, infection risks, and/or a sterility assurance level of 10^{−Reference Alfred, Catchpole, Huffer, Fredendall and Taaffe6} . ^{Reference Rutala, Kanamori, Sickbert-Bennett and Weber7} Current assessment tools (eg, visual and adenosine triphosphate [ATP]) are not predictive of microbial contamination or infection risks. Investigators have demonstrated that visual assessment and ATP lack the sensitivity required to ensure effective decontamination. ^{Reference Alfa, Fatima and Olson8}

Our research was limited by the fact that we did not assess other factors than might affect sterilization, such as microbial contamination in lumened instruments, or transfer and storage conditions, which could enhance microbial growth or biofilm formation.

These results illustrate that steam sterilization is the most effective with the largest margin of safety, followed by ETO and HPGP. The data demonstrate how important cleaning is prior to sterilization because salt, blood, oils, and organic matter left on instruments can interfere with low-temperature sterilization. ^{Reference Rutala and Weber1–Reference Diab-Elschahawi, Blacky, Bachhofner and Koller5} The issue of “how clean is clean enough” remains unresolved but various cleaning markers (eg, protein ≤6.4 µg/cm²) of when to consider a device clean can be used by manufacturers when preparing reprocessing instructions for users. ^{9,Reference Richter10} However, these cleaning markers must be available in real-time to instrument reprocessing technicians.