Sterilization and Disinfection




Abstract


Sterilization and disinfection are the basic components of hospital infection control activities. Every day, a number of hospitals are performing various surgical procedures. Even more number of invasive procedures are being performed in different health care facilities. The medical device or the surgical instrument that comes in contact with the sterile tissue or the mucus membrane of the patient during the various processes is associated with increased risk of introduction of pathogens into the patient’s body. Moreover, there is chance of transmission of infection from patient to patient; from patient or to health care personnel, and vice versa; or from the environment to the patient through the improper sterilized or disinfected devices. Hence, medical personnel, laboratory people and the health care providers should have better knowledge regarding these techniques to prevent the spread of these pathogens.




Keywords

Bundle approach, Disinfection techniques, Health care–associated infections, Medical equipment, Sterilization techniques

 






  • Outline



  • Background 930




    • Classification of Medical Devices and/or Equipment 930




  • Recommendation of Preferred Methods for Various Medical Devices 931




    • Sterilization, Disinfection, and Cleaning in the Health Care Facilities 931




  • Recommendation for the Cleaning and Decontamination of Environmental Surfaces 931



  • Recommendation for Blood Spill on the Surface 932



  • Cleaning and Disinfection of Medical Instruments 933



  • Cleaning and Reprocessing of Patient Care Equipment 933




    • Reprocessing of the Critical Items 935



    • Reprocessing of Semicritical Items 935



    • Reprocessing of Noncritical Items 935




  • Reprocessing of Respiratory Apparatus and Endoscopes 935




    • Ventilators 935



    • Routine Ventilator Care 935



    • Humidifiers 936



    • Nebulizer 936



    • Anesthetic Equipment 936



    • Pulmonary Screening Device 936




  • Reprocessing of Endoscopes 936




    • Cleaning 937



    • Disinfection 937



    • Rinse and Dry 937



    • Store 937



    • Risk of Nonendoscopic Transmission of Infection 937



    • Processing of Other Scopes 938




  • Specific Issues 938




    • Cleaning and Disinfecting Surface and Floors 938



    • Inactivation of Emerging/Resistant Bacteria 938



    • Disinfection of Human Immunodeficiency Virus, Hepatitis B Virus, Hepatitis C Virus, and Tuberculosis-Contaminated Devices 938




  • Special Precaution for Inactivation of Creutzfeldt–Jakob Disease 939



  • Health Care–Associated Infections 940




    • Definition 940



    • Common Health Care–Associated Infections 940




  • Infections in Operating Rooms and Intensive Care Units 940




    • Source 940



    • Measures to Reduce Health Care–Associated Infection 940



    • Design of Operating Room 941



    • Ventilation and Cleaning of the Operating Rooms 941



    • Microbiological Sampling 941



    • Health Care–Associated Infections in the Intensive Care Units and Its Prevention 942



    • Bundle Approach for Reducing Infection 942




  • Conclusion 943



  • References 943




Background


Sterilization and disinfection are the basic components of hospital infection control activities. Every day, a number of hospitals are performing various surgical procedures. Even more number of invasive procedures are being performed in different health care facilities. The medical device or the surgical instrument that comes in contact with the sterile tissue or the mucus membrane of the patient during the various processes is associated with increased risk of introduction of pathogens into the patient’s body. Moreover, there is chance of transmission of infection from patient to patient; from patient or to health care personnel, and vice versa [e.g., hepatitis B virus (HBV)]; or from the environment to the patient (e.g., Pseudomonas aeruginosa , Acinetobacter spp.) through the improper sterilized or disinfected devices. A number of outbreaks and infections were reported in the hospital setup because of improperly sterilized devices. Many infections were reported throughout the world due to use of contaminated endoscopes. Hence, adequate decontamination techniques for medical and surgical devices are needed in all the health care facilities. The health care providers are equally responsible for the reduction and elimination of such infections. Every hospital should have its own guidelines of sterilizing and disinfecting items on the basis of their intended use of medical devices and associated infections. Currently, there is an increase in frequency of newly emerging and multidrug-resistant pathogens in all health care centers for which only few/if any treatments are available. Hence, the medical personnel, laboratory people, and health care providers should have better knowledge regarding these techniques to prevent the spread of these pathogens.


There is no uniform definition or standards for sterilization, disinfection, and cleaning. However, the Clinical and Laboratory Standards Institute has defined some minimum inhibitory concentration testing–based recommendations, which are currently standardized by the International Organization of Standardization. The norms were first established in 2004, and later in 2010, new guidelines were published.


Sterilization : Sterilization is defined as a process of complete elimination or destruction of all forms of microbial life (i.e., both vegetative and spore forms), which is carried out by various physical and chemical methods. Technically, there is reduction ≥10 6 log colony forming units (CFU) of the most resistant spores achieved at the half-time of a regular cycle.


Chemical sterilant : These are chemicals used for a longer duration (3–12 h) to destroy all forms of microbes, e.g., peracetic acid (PAA) (0.2%), glutaraldehyde (≥2.4%), ortho -phthalaldehyde (OPA) (0.55%), and hydrogen peroxide (7.5%).


Disinfection : Disinfection is defined as a process of complete elimination of vegetative forms of microorganisms except the bacterial spores from inanimate objects. Technically, there is reduction of ≥10 3 log CFU of microorganisms by this method without spores.


High-level disinfectant (HLD) : Used for shorter duration and able to kill 10 6 log microorganisms except spores, e.g., glutaraldehyde (≥2.0%), OPA (0.55%), hydrogen peroxide (7.5%), hypochlorite (650–675 ppm), and hypochlorous acid (400–450 ppm).


Intermediate level disinfectant (ILD) : These disinfectants act against Mycobacterium tuberculosis and are mainly used for noncritical items contaminated with blood/body fluids.


Low-level disinfectant (LLD) : LLDs are used to remove the vegetative form of bacteria, few fungi, and some enveloped viruses from the noncritical items, e.g., 3% hydrogen peroxide, quaternary ammonium compound, diluted glutaraldehyde, phenolics, etc.


Decontamination and cleaning : Decontamination is the process of removal of pathogenic microorganisms from objects so that they are safe to handle. Cleaning is defined as removal of visible soil (e.g., organic and inorganic materials) from the surfaces and objects. Technically, it achieves minimum reduction of ≥1 log CFU of microorganisms.


Antisepsis : Antisepsis is a process of removal of germs from the skin. When it is related to the patient’s skin, it means disinfection of living tissue or skin. When it is related to the health care worker, it means reduction or removal of transient microbe from the skin.


Germicide : It is the agent that destroys germs. It includes both antiseptics and disinfectants. The type of microorganism is identified from the prefix (e.g., virucide, fungicide, bactericide, sporicide, and tuberculocide).


Classification of Medical Devices and/or Equipment


The principal goal of cleaning, disinfection, and sterilization is to reduce the number of microorganisms on the device to such a level that the probability of transmission of infection will be nil. The risk of transmission of infection depends on the type of device. For example, in case of blood pressure–measuring cuff, the device that comes in contact with the skin carries least risk of transmission of disease. On the other hand, devices that come in contact with the neural tissue of a patient suffering from Creutzfeldt–Jakob disease (CJD) have high risk of transmission of infection. To reduce the potential risks of transmission of infection through different devices, Earle H. Spaulding in 1968 proposed a classification to define the desired level of antimicrobial killing for different devices. He categorized the devices into three categories depending on the potential risk of transmission of infectious agents: critical, semicritical, and noncritical ( Table 59.1 ).



Table 59.1

Spaulding’s Classification of Devices




























Device/Item Definition Risk of Infection Example Reprocessing Procedure
Critical Medical device that is intended to enter a normally sterile environment, sterile tissue, or the vasculature High Surgical instrument, cardiac catheter, implants, needle, ultrasound probes used in sterile body cavity Sterilization by steam, plasma, or ethylene oxide
Semicritical Devices that are intended to come in contact with the mucous membrane or nonintact skin High/intermediate Flexible endoscope, respiratory therapy equipment, manometry probes, diaphragm-fitting rings, laryngoscope blades Sterilization desirable, high-level disinfectants
Noncritical Devices come in contact with intact skin Low Blood pressure cuff, stethoscope Intermediate or low-level disinfectant


This simple classification of Spaulding’s needs to be revised, as it did not address the devices that come in contact with the mucous membrane (e.g., endoscope), biopsy forceps touching the breach sterile tissue, heat-sensitive items, and prions. The Centers for Disease Control and Prevention (CDC) in 1991 proposed an additional category to Spaulding’s classification as “environmental surfaces” to represent the surfaces that usually do not come in contact with patient. Environmental surfaces can be further subgrouped as clinical contact surfaces (medical equipment or high-touch surfaces) and housekeeping surfaces. CDC defines clinical contact surfaces as the areas that act like reservoirs of microorganisms, e.g., hands of health care workers. High-touch surfaces such as telephone, light switch board, bedrails, computer, door handle, and medical equipment like ventilator, X-ray machines, and hemodialysis machines are the contacting equipment that subsequently contact the patient. CDC had issued guidelines for hand washing and hospital environmental control. Different LLDs and ILDs that can be used to disinfect the clinical contact surfaces were approved by the Environmental Protection Agency (EPA). The housekeeping surfaces such as walls, floor, and sinks carry very low risk of transmission of infection. So, disinfection of such surfaces is less frequent in comparison to the previous one.




Recommendation of Preferred Methods for Various Medical Devices


The antimicrobial spectra of different methods are different from each other ( Fig. 59.1 ). Hence, health care personnel should have adequate knowledge for the selection and recommendation of different sterilization and disinfection methods ( Tables 59.2 and 59.3 ). A brief knowledge about the compatibility, toxicity, odor, and irritability due to various agents/methods is essential and useful for achieving adequate decontamination.




Figure 59.1


Increasing order of resistance of microorganisms to sterilization and different levels of disinfectants.


Table 59.2

Different Methods of Sterilization With Examples





























Methods of Sterilization Example Target Application
High temperature Steam, dry heat All forms of microbes (vegetative and spore)


  • Heat-tolerant surgical instruments



  • Semicritical patient care items

Low temperature Ethylene oxide gas, hydrogen peroxide, ozone, gas plasma, gaseous chlorine dioxide, ionizing radiation, pulsed light Gram-positive bacteria, gram-negative bacteria, mycobacteria, lipid-enveloped viruses, large nonenveloped viruses, spores, cyst, trophozoite, coccidia


  • Heat-sensitive critical



  • Semicritical patient care items

Liquid chemicals Chemical sterilants Prions (resistant to any form of sterilization)


  • Heat-sensitive critical items



  • Semicritical patient care items ( that can be immersed )

Others Filtration


  • Serum



  • Vaccines



  • Antibiotics



Table 59.3

Different Methods of Disinfection With Examples



































Methods of Disinfection Example Target Application
HLD
Heat Pasteurization (∼50 min) All vegetative forms of microorganisms


  • Heat-tolerant semicritical patient care items (respiratory therapy equipment)

Chemicals Chemical sterilants Gram-positive bacteria, gram-negative bacteria, mycobacteria, lipid-enveloped viruses, large nonenveloped viruses, spores, cyst, trophozoite, coccidian


  • Heat-sensitive semicritical patient care items (e.g., GI endoscopes, bronchoscopes)

ILD
Chemicals EPA-registered with tuberculocidal activity (e.g., chlorine-based products, phenolics) Gram-positive bacteria, gram-negative bacteria, enveloped and nonenveloped viruses, mycobacteria


  • Soiled noncritical items



  • Surfaces contaminated with blood



  • Devices contaminated with body fluid/feces/sputum/ Mycobacterium

LLD
Chemicals EPA registered but without tuberculocidal activity (e.g., chlorine-based products, phenolics, quaternary ammonium compounds, 70–90% alcohol) Vegetative forms of bacteria, lipophilic viruses and some fungi


  • Noncritical patient care items


EPA , Environmental Protection Agency; GI , gastrointestinal; HLD , high-level disinfectant; ILD , intermediate-level disinfectant; LLD , low-level disinfectant.


The various chemicals used for the process of antisepsis or skin disinfection are chloroxylenols, anilides, hexachloraphene, polymeric biguanides, alexidine, diamidines, and triclosan.


Sterilization, Disinfection, and Cleaning in the Health Care Facilities


Sterilization, disinfection, and cleaning in health care facilities include disinfection and cleaning of environmental surfaces with/without cleaning and reprocessing the medical equipment. The former includes mainly the noncritical items such as surfaces, floors, and high-contact surfaces (sinks, telephones, switches board, bed railings, trolleys etc.). It is observed that regular cleaning of all these housekeeping surfaces dramatically reduces the transmission of the infection.




Recommendation for the Cleaning and Decontamination of Environmental Surfaces





  • The space for cleaning and other work should be clearly demarcated and separated by walls.



  • The hospital staffs should be properly trained regarding the cleaning and decontamination practices of hospital surfaces.



  • The staffs should wear personal prophylactic equipment (PPE), i.e., gowns, gloves, masks, and boots. There must be separate area for removing PPE.



  • Fresh preparation of detergents or disinfectants should be made every day and used with the appropriate dilution as per the manufacturer instruction.



  • Wet mopping of floors should be encouraged as dry mopping generates dust aerosols.



  • Avoid using HLD for environmental surfaces of the hospital and offices. Mopping of the hospital surfaces should be done using detergent. Table tops and counters should also be cleaned regularly by detergent only.



  • Mopping of high-risk areas such as the intensive care units (ICUs), burn wards, transplant units, isolation wards, operation theaters (OTs), and dialysis machines should be done using HLD instead of detergent. Cleaning by vacuum pump and use of high-efficiency particulate air (HEPA) filters for the exhaust are preferred in these places.





Recommendation for Blood Spill on the Surface





  • Cleaning and decontamination of the hospital surfaces having spilled blood is done as per the recommendation of Occupational Safety and Health Administration/World Health Organization/CDC.



  • ILD or disinfectants with tuberculocidal activity should be used for blood spill in the hospital surfaces.



  • For decontamination of small amount of blood spills (<10 mL), sodium hypochlorite solution is used with a dilution of 1:100. For spill >10 mL, sodium hypochlorite with 1:10 dilution is used for the first application. The organic matter should be cleaned with absorbent material, and final disinfection may be done using sodium hypochlorite solution with 1:100 dilution.





Cleaning and Disinfection of Medical Instruments


The cleaning and disinfection of medical equipment depends on their physical nature, character of the material it is made up of, lumen size, etc. Thorough cleaning is preferred before the use of the disinfectants as cleaning effectively removes majority of the microbes from the equipment.




  • Staffs should be properly educated and trained regarding the cleaning procedure, physical and chemical nature of the instruments, nature of disinfectants, etc. All the staffs during the process should use PPE.



  • Dry organic materials are difficult to remove from the instrument. Hence, drying should be avoided by immersing the equipment in the detergent or disinfectant solution prior to cleaning. The soaked matter can be cleaned by manual scrubbing and rubbing with brush or automated scrubber and thoroughly washed with water under pressure. Avoid prolonged or overnight soaking of the devices.



  • The time of exposure, and concentration of the detergent or disinfectant, should be properly maintained as mentioned in the literature. Too low concentration may not work effectively to remove the organic materials or microorganisms.



  • The pH of the disinfectant should be properly obtained as per the manufacturer’s instruction. Delicate articles should be processed in neutral pH.



  • Enzymes like proteases may be added to the solution to fasten the cleaning action. Enzymatic cleaners with neutral pH are preferred to avoid the damage of the articles. For example, in case of flexible endoscope, neutral pH detergent with enzymatic action is preferred. A new nonenzyme product [hydrogen peroxide based, US Food and Drug Administration (FDA) cleared] has been found to be very effective as cleaning agent.





Cleaning and Reprocessing of Patient Care Equipment


Patients care equipment are divided into three categories (critical, semicritical, and noncritical) depending on the intended use and risk of transmission of infection. The cleaning and reprocessing protocol for each category are detailed in Tables 59.4–59.6 .



Table 59.4

Cleaning and Reprocessing of Critical Patient Care Items





































Objects Mode of Reprocessing
Catheters (cardiac, arterial, urine) Sterile, single use
Needles Disposable, single use
Implantable devices Sterile, single use
Intravascular devices Sterile, single use
Surgical instruments Heat sterilization in autoclaves
Arterial pressure transducers Sterilize by heat/low-temperature (H 2 O 2 )/ethylene oxide
Diagnostic ultrasound Sterilization/HLD as per manufacturer’s instruction
Heart–lung oxygenator surfaces Heat/low-temperature sterilization
Hemodialysis and plasmapheresis Heat/low-temperature sterilization
Neurological test needles Disposable, if using reusable: Sterilize with heat/steam/sterilize by EtO

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Sep 5, 2019 | Posted by in ANESTHESIA | Comments Off on Sterilization and Disinfection
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