Sterilization and Disinfection

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).

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.

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

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 .

Reprocessing of Respiratory Apparatus and Endoscopes

Respiratory apparatus such as ventilators, humidifiers, nebulizers, pulmonary screening devices, anesthetic equipment, laryngoscope and its blade, and suction equipment are most important in the ICU setup because of its association with the risk of transmission of infection. Proper cleaning and infection preventive measures should be followed while handling these instruments as they are highly associated with the transmission of infection from one patient to other. They come in contact with the mucous membrane of the body, are included in the semicritical item category, and are sterilized or disinfected with the HLD.