Sterilization and disinfection

Table of Contents
Unit 7. 4
Sterilization and Disinfection. 4
Learning objectives: 5
Personal hygiene. 5
Activity 5
Examples of practiced personal hygiene. 5
General 5
Hands 6
Hand washing. 7
Activity. 7
Learn proper hand washing techniques. 7
Occupational Hygiene. 9
Chemical hazards. 9
Physical hazards. 9
Biological hazards. 9
Pathogens. 9
Bacteria. 9
Viruses. 10
Fungi 10
Parasites. 11
Transmission of pathogens. 11
Chain of infection. 12
Activity 13
Nosocomial infections. 14
Activity 14
Main routes of transmission of infections. 14
Predisposition to infection. 15
Prevention. 15
Isolation 15
Hand washing and gloving. 17
Aprons 17
Universal or Standard Precautions for Control of Infection. 18
Isolation precautions in hospitals. 18
Source. 18
Host 19
Transmission. 19
Fundamentals of isolation precautions. 19
Hand washing and gloving. 19
Patient placement 19
Transport of Infected Patients. 20
Masks, respiratory protection, eye protection, face shields. 20
Gowns and protective apparel 20
Patient-care equipment and articles. 21
Linen and laundry. 21
Dishes, glasses, cups, and eating utensils. 21
Routine and terminal cleaning. 21
Asepsis. 23
Activity 23
Activity 24
Sterilisation. 25
Physical sterilisation. 25
Heat 25
Autoclaving/Steam under Pressure. 26
Filtration. 29
Chemical sterilisation. 29
Safe disposal of sharp instruments. 37
Activity. 37
Class room evaluation. 39


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Unit 7
Sterilization and Disinfection
Learning objectives:
After completing unit 7 dispenser students will be able to:
describe and demonstrate personal hygiene and hygiene of their work environment
list rules of general safety
explain the chain of infection
explain the differences between medical asepsis, surgical asepsis, disinfection and sterilization
explain general or universal precaution techniques and isolation precaution techniques
describe nosocomial infections and their risk to clients
describe risk of contracting infection to healthcare professionals
demonstrate proper hand washing
prepare and sterilize instruments
carry out safe disposal of instruments (syringes, needles, disposable medical/surgical) equipment.
Personal hygiene
Activity
Discuss with your class their understanding of personal hygiene.
Ask students to give examples of good personal hygiene prompting them about general, hand and other types of personal hygiene.
Personal hygiene is the basic concept of cleaning, grooming and caring for our bodies. While it is an important part of people’s daily lives at home, personal hygiene is also important for workers’ health and safety in the workplace. Workers who pay attention to personal hygiene can prevent the spread of germs and disease. They can also reduce their exposures to chemicals and contaminants, and avoid developing skin allergies, other skin conditions, and chemical sensitivities.
Examples of practiced personal hygiene
General
Washing the body and hair frequently
Cutting / cleaning nails
Cutting hair
Washing clothes and cleaning home
Changing bed sheets frequently.
Hands
Some germs can stay alive on hands for up to three hours and in that time they can spread to all the things touched – including food and other people. Hands should be washed regularly throughout the day and especially at these times:
Before:
· Preparing and eating food
· Caring for patients, changing dressings, giving medicines
· Looking after babies or the elderly
· Putting in contact lenses in the eyes
Between:
· Handling raw foods (meat, fish, eggs and poultry) and touching any other food or kitchen utensils (knives, spoons etc)
After:
· Touching bare human body parts other than clean hands and clean, exposed portions of arms
· Food preparation
· Handling raw foods, particularly meat, fish, eggs and poultry
· Eating or drinking
· Going to the toilet
· Touching rubbish/waste bins
· Handling soiled equipment or utensils
· Changing nappies
· Caring for the sick, especially those with gastro-intestinal disorders (e.g. diarrhoea)
· Coughing or sneezing, using a handkerchief or disposable tissue
· Handling and stroking pets or farm animals

Others
· As mouth is the area most prone to collecting harmful bacteria and generating infections, a person’s mouth hygiene should be good. Mouth hygiene means taking care of the teeth and gums, and treating or preventing bad breath by:
o brushing teeth with toothpaste at least two times per day, if not after every meal, to minimize the amount of bacteria in the mouth which leads to tooth decay and gum disease. This also helps treat and prevent bad breath
o flossing teeth at least once a day, usually before going to bed at night. This reduces plaque in the more difficult to reach places—between teeth and at the back of the molars
o rinsing mouth with antibacterial mouthwashes (such as Listerine)
o visiting dentist at least every six months
· Avoid contact with bodily fluids, such as blood, stools, urine, and vomit
· Avoid handling foods for others if one is ill, especially with any gastrointestinal problems
· Do not sneeze or cough near foods
· Cover all cuts, burns and sores and change dressings regularly – pay extra attention to any open wounds on hands and arms
· Wear clean undergarments and clothing.
Hand washing
Since person-to-person spread can play a significant role in the spread of some gastrointestinal tract pathogens, hand hygiene is a critical element of any disease outbreak prevention and control strategy.
Activity
Learn proper hand washing techniques
Step 1
Wash hands using soap and warm, running water. Rub hands vigorously during washing for at least 20 seconds with special attention paid to the backs of the hands, wrists, between the fingers and around and under the fingernails.
Step 2
Rinse hands well while leaving the water running.
Step 3
With the water running, dry hands with a single-use towel.
Step 4
Turn off the water using a paper towel, covering washed hands to prevent re-contamination.


Adapted from the US Department of Health and Human Services, Centers for Disease Control and Prevention, Atlanta, Georgia.
Occupational Hygiene
"Occupational Hygiene is the discipline of anticipating, recognizing, evaluating and controlling health hazards in the working environment with the objective of protecting worker health and well-being and safeguarding the community at large.
(International Occupational Hygiene Association definition)
Occupational Hygiene deals with the assessment and control of chemical, physical or biological hazards in the workplace that could cause disease or discomfort. It manages people and programs for the preservation of health and well-being of those who enter the workplace.
Chemical hazards
Chemical hazard arises from contamination with harmful or potentially harmful chemicals. When chemicals are not properly managed, they can have harmful consequences, such as toxic fumes, fires, and explosions. This may result in death and injury to people, damage to physical property, and severe effects on the environment.
Physical hazards
Physical hazards are those substances which threaten a person’s physical safety. They may include noise (elevated sound levels), temperature extremes (too hot or too cold), illumination extremes, ionizing or non-ionizing radiation, indoor air quality and safety.
Biological hazards
A biological hazard is an organism, or substance derived from an organism, that poses a threat to human health. This can include medical waste, samples of a microorganism, virus or toxin (from a biological source) that can impact human health. It can also include substances harmful to animals. E.g. exposure to viruses causing chicken pox, hepatitis A, B and C, SARS, and dengue fever.
Pathogens
A pathogen is a living organism that causes disease. Following are different types of common pathogens that cause diseases:
Bacteria
Bacteria are one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains. They reproduce independently. Although the vast majority of bacteria are harmless or beneficial to humans, and usually exist on the skin, gut, or in the nose without causing any disease at all, a few bacteria cause infectious diseases. E.g. Mycobacterium tuberculosis (which cause tuberculosis), Streptococcus pneumoniae (which cause pneumonia and skin infections), and Shigella, Campylobacter and Salmonella (which cause food borne illnesses). Pathogenic bacteria also cause infections such as tetanus, diphtheria, syphilis and leprosy. Bacterial infections may be treated with antibiotics which are of many different types.
A small number of bacteria produce spores. Spores are dormant, tough, and non-reproductive structures. The primary function of spores is to ensure the survival of a bacterium through periods of environmental stress. They are, therefore, resistant to most sterilizing techniques such as extreme heat and radiation. Spores can, however, be destroyed by burning or autoclaving. Exposure to extreme heat for a long enough period will generally have some effect, though many spores can survive hours of boiling or cooking. Prolonged exposure to high energy radiation, such as x-rays and gamma rays, will also kill most spores.
Spores are commonly found in soil and water, where they may survive for long periods of time. Examples of bacteria having spores include Clostridium tetani, the pathogen which causes the disease tetanus (See Unit 5, Basic concepts of management of EPI-related diseases).
Viruses
Viruses are the smallest of all infectious agents, averaging about 100 billionths of a meter in length. Viruses are much smaller than bacteria. They cause familiar infectious diseases such as the common cold, chicken pox, measles, mumps, and influenza. They also cause severe illnesses such as AIDS, smallpox, hepatitis B and C, and HIV.
They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. This eventually kills the cells, which can make the person sick.
Viral infections are hard to treat because viruses live inside body's cells and are "protected" from medicines, which usually move through the bloodstream. Antibiotics do not work for viral infections. There are a few antiviral medicines available. Vaccines can help prevent getting many viral diseases.
Fungi
Fungi are a type of plant that can infect people. Yeasts, molds, and mushrooms are all examples of fungi. Fungi live in air, in soil, on plants and in water. Some live in the human body. Only about half of all types of fungi are harmful.
Some fungi reproduce by spreading microscopic spores. These spores are often present in the air, where they can be inhaled or come into contact with the surfaces of a person's body. Consequently, fungal infections usually begin in the lungs or on the skin. Of the wide variety of fungal spores that land on the skin or are inhaled into the lungs, most do not cause infection. A person is more likely to get a fungal infection if they have a weakened immune system (e.g. if a person has AIDS), take steroids, take antibiotics for a bacterial infection, or have diabetes. Certain types of fungi (such as Candida) are normally present on body surfaces or in the intestines. Although normally harmless, these fungi sometimes cause local infections of the skin and nails.
Some common fungal infections are athlete's foot (scaling and sogginess of the skin, commonly of the web spaces between the toes), ringworm of the nails (malformed, thickened and crumbly nails), and ringworm of the scalp (hair loss with inflammation in the affected area).
Fungi can be difficult to kill; for skin and nail infections, medicine can be applied directly to the infected area. Oral antifungal medicines are also available for serious infections.
Parasites
Parasites are organisms that grow, feed, and are sheltered on or within a human body (or other organisms) without providing any benefit to their host. Many parasites do not cause disease per se. Parasitic diseases can affect practically all living organisms, from plants to mammals. Parasites could be single-cell or multi-cellular. Single-cell parasites tend to be at least 10 times larger than bacteria, or about 0.01 millimeter long. Multi cellular parasites are so large they can usually be seen with the naked eye. Tapeworms, for instance, can reach a length of 6 meters (20 feet).
Food and water are the most common sources of parasite transmission. Since we eat and drink water frequently throughout the day, our exposure to parasites is constant. Examples of parasites causing human disease are Plasmodium malariae (which causes malaria), beef tapeworm, hookworm, roundworm, and liver fluke.
Transmission of pathogens
One of the primary pathways by which food or water become contaminated is from the release of untreated sewage into a drinking water supply or onto cropland, with the result that people who eat or drink contaminated sources become infected. This is the typical mode of transmission for the infectious agents of (at least) cholera, hepatitis A, polio.
Chain of infection
Chain of infection means how infections are spread. It is a circle of six links which is used to understand the infection process. For an infection to occur and spread each of the six links of the cycle or chain must take place. Removing any link in the chain will bring about a cessation of the infectious cycle; therefore, knowing and identifying the links in the chain and performing the appropriate course of action to break a link will halt the continuous spread of the infection. In simple terms breaking a link stops the spread of the infection.
The links are: infectious agent, reservoir, portal of exit from the reservoir, mode of transmission, and portal of entry into a susceptible host as described below:
i. Infectious agent
A microbial organism (germ) with the ability to cause disease. Infectious agents are bacteria, viruses, fungi, and parasites. The greater the organism's virulence (ability to grow and multiply), invasiveness (ability to enter tissue) and pathogenicity (ability to cause disease), the greater the possibility that the organism will cause an infection.
ii. Reservoir
A place within which infectious agents can live and reproduce. For example, infectious agents live in human beings, animals, and inanimate objects such as water, table tops, and doorknobs.
iii. Portal of exit
A place of exit providing a way for an infectious agent to leave the reservoir. For example, the infectious agent may leave the reservoir through the nose or mouth when someone sneezes or coughs, or through the stools of an infected intestine.
iv. Mode of transmission
Method of transfer by which the infectious agent moves or is carried from one place to another. E.g. the hands of the health care worker may carry bacteria from one person to another.
v. Portal of entry
An opening allowing the infectious agent to enter the host. Portals include body openings (nose, mouth, anus, vagina etc.) or breaks in the skin etc. Portals also result from tubes placed in body cavities, such as urinary catheters, or from punctures produced by invasive procedures such as intravenous fluid replacement.
vi. Susceptible host
A person who cannot resist an infectious agent invading the body, multiplying, and resulting in infection. The host is susceptible to the disease, lacking immunity or physical resistance to overcome the invasion by the pathogenic microorganism.

Figure1: Model of chain of infection


Activity
This activity will be done with six students who will represent a ‘chain of infection’. Each student is to assume the role of one of the six links. All students form a circle holding each other’s hands. Each link of the circle is to explain who they are and how they help in spreading the infection.
Nosocomial infections
Nosocomial infections (or hospital-acquired infections) are infections which are a result of treatment in a hospital or other healthcare facility, but secondary to the patient's original condition. Infections are considered nosocomial if they first appear 48 hours or more after hospital admission or within 30 days after discharge. The most common nosocomial infections are of the urinary tract, and various pneumonias.
Activity
Discuss with your class why infection spreads so easily in hospital wards.
Discuss with your class how infection spreads in hospital wards.
Discuss how the spread of infection could be prevented.
Reasons why nosocomial infections are so common include:
· Hospitals house large numbers of people who are sick and whose immune systems (system with the ability to fight off infections) are often in a weakened state;
· People who are hospitalized are generally very sick people;
· Medical staff move from patient to patient, providing a way for germs to spread;
· Many medical procedures bypass the body's natural protective barriers;
· Routine use of antibiotics in hospitals leads to the emergence of bacteria which are resistant to the usual antibiotics.
Thorough hand washing and/or use of alcohol rubs by all medical staff before each patient contact is one of the most effective ways to combat nosocomial infections. More careful use of antibiotics is also considered vital.
Germs are transmitted in hospitals by several routes, and the same germs may be transmitted by more than one route.
Main routes of transmission of infections
There are five main routes of transmission of infections in hospital facilities and outside hospitals: contact, droplet, airborne, common vehicle, and vector borne.
i. Contact transmission, is the most important and frequent mode of transmission of nosocomial infections, is divided into two subgroups:
a. Direct-contact transmission involves a direct body surface-to-body surface contact and physical transfer of germs between a susceptible host and an infected person, such as occurs when a staff member turns a patient or gives a patient a bath or can occur between two patients.
b. Indirect-contact transmission involves contact of a susceptible host with a contaminated object, such as contaminated instruments, needles, or dressings, or contaminated hands that are not washed and gloves that are not changed between patients.
ii. Droplet transmission occurs when droplets are generated from the source person mainly during coughing, sneezing, and talking, and during the performance of certain procedures such as bronchoscopy. Transmission occurs when droplets containing germs from the infected person are propelled a short distance through the air and deposited on the host's body.
iii. Airborne transmission occurs by dissemination of droplets containing germs that remain suspended in the air for long periods of time or dust particles containing the germs. Germs carried in this manner can be dispersed widely by air and may become inhaled by a susceptible host within the same room or over a longer distance from the source patient, depending on environmental factors. Germs transmitted by airborne transmission include Mycobacterium tuberculosis and some viruses.
iv. Common vehicle transmission applies to germs transmitted by contaminated items such as food, water, medications, devices, and equipment.
v. Vector borne transmission occurs when vectors such as mosquitoes, flies, rats, and other vermin transmit microorganisms.
Predisposition to infection
Factors predisposing a patient to nosocomial infection are:
i. People in hospitals are usually already in a poor state of health, impairing their defense against bacteria – old age or premature birth along with immunodeficiency (due to drugs, illness, or radiation) present a general risk, while some diseases can present specific risks.
ii. Invasive devices, for instance intubation tubes, catheters, surgical drains and tracheostomy tubes all bypass the body’s natural lines of defense against germs and provide an easy route for infection.
iii. A patient’s treatment itself can leave them vulnerable to infection – immune-suppression, antacid treatment, antibiotic therapy and recurrent blood transfusions.
Prevention
Isolation
Isolation precautions are designed to prevent transmission of germs by common routes in hospitals. Because agent and host factors are more difficult to control, interruption of transfer of germs is directed primarily at transmission.

Hand washing and gloving
Hand washing is the single most important measure to reduce the risks of transmitting germs from one person to another or from one site to another on the same patient. Washing hands as promptly and thoroughly as possible between patient contacts and after contact with blood, body fluids, secretions, excretions, and equipment or articles contaminated by them is an important component of infection control and isolation precautions.
In addition to hand washing, gloves play an important role in reducing the risks of transmission of germs. Gloves are worn for three important reasons in hospitals.
· First, gloves are worn to provide a protective barrier and to prevent contamination of the hands when touching blood, body fluids, secretions, excretions, mucous membranes and non-intact skin
· Second, gloves are worn to reduce the likelihood that germs present on the hands of staff will be transmitted to patients during invasive or other patient-care procedures that involve touching a patient's mucous membranes and non-intact skin.
· Third, gloves are worn to reduce the likelihood that hands of staff contaminated with germs from a patient or a fomite can transmit these germs to another patient. In this situation, gloves must be changed between patient contacts and hands washed after gloves are removed. Wearing gloves does not replace the need for hand washing, because gloves may have small, in-apparent defects or may be torn during use, and hands can become contaminated during removal of gloves.
Aprons
Wearing an apron during patient care reduces the risk of infection. The apron should either be disposable or be used only when caring for a specific patient
Universal or Standard Precautions for Control of Infection
Universal precautions (or Standard precautions) are infection control techniques; they refer to the practice of avoiding contact with patients' bodily fluids, by means of the wearing of nonporous articles such as medical gloves, goggles, and face shields and of disposing instruments, especially scalpels and needles, in a sharps container.
Universal precautions were recommended following the AIDS outbreak in the 1980s. Every patient is treated as if they are infected and therefore precautions are taken to minimize risk. Essentially, universal precautions are good hygiene habits, such as hand washing and the use of gloves and other barriers, correct sharps handling, and aseptic techniques.
Additional precautions are used in addition to universal precautions for patients who are known or suspected to have an infectious condition e.g. tuberculosis, mumps, rubella, whooping cough.
Universal precautions should be practiced in any environment where workers are exposed to bodily fluids, such as blood, semen, vaginal secretions, cerebrospinal fluid etc. Bodily fluids that do not require such precautions include stools, nasal secretions, urine, vomitus, sweat, sputum and saliva.
Universal precautions are recommended not only for doctors, nurses and patients, but for health care support workers. Some support workers, most notably laundry and kitchen staff, may be required to come into contact with patients or bodily fluids.
Protective clothing may include but is not limited to:
Barrier gowns
Gloves
Eyewear (goggles or glasses)
Face shields
Hair nets
Shoe coverings.
Isolation precautions in hospitals
Transmission of infection within a hospital requires three elements: a source of infecting microorganisms, a susceptible host, and a means of transmission for the microorganism.
Source
Human sources of the infecting microorganisms in hospitals may be patients, staff, or visitors. Other sources of infecting microorganisms can be the various hospital objects that have become contaminated, including equipment and medications.

Host
Resistance among persons to disease causing germs varies greatly with some persons developing clinical disease while others not. Host factors such as age, underlying diseases, treatments with antibiotics, corticosteroids, or some other drugs, irradiation, and breaks in the first line of defense mechanisms caused by such factors as surgical operations, anesthesia, and indwelling catheters may render patients more susceptible to infection.

Transmission
See the Section on nosocomial infections.

Fundamentals of isolation precautions
A variety of infection control measures are used for decreasing the risk of transmission of germs in hospitals. These are as follows:
Hand washing and gloving
See the Section on Nosocomial infections.

Patient placement
Appropriate patient placement is a significant component of isolation precautions. A private room is important to prevent direct- or indirect-contact transmission. When possible, a patient with highly transmissible germs is placed in a private room with hand washing and toilet facilities, to reduce opportunities for transmission of germs. When a private room is not available, an infected patient is placed with an appropriate roommate. Patients infected by the same microorganism usually can share a room, provided they are not infected with other potentially transmissible microorganisms and the likelihood of re-infection with the same organism is minimal.

Transport of Infected Patients
Limiting the movement and transport of patients infected with disease causing germs and ensuring that such patients leave their rooms only for essential purposes reduces opportunities for transmission of germs in hospitals. When patient transport is necessary, it is important that:
1) appropriate barriers (e.g., masks) are worn by the patient
2) staff in the area to which the patient is to be taken are notified of the patient’s arrival and of the precautions to be used to reduce the risk of transmission of infectious germs, and
3) patients are informed of ways by which they can assist in preventing the transmission of their infectious germs to others.

Masks, respiratory protection, eye protection, face shields
Various types of masks, goggles, and face shields are worn alone or in combination to provide barrier protection. A mask that covers both the nose and the mouth, and goggles or a face shield are worn by hospital personnel during procedures and patient-care activities that are likely to generate splashes or sprays of blood, body fluids, secretions, or excretions to provide protection of the mucous membranes of the eyes, nose, and mouth from contact transmission of pathogens. A surgical mask generally is worn by hospital personnel to provide protection against spread of infectious large-particle droplets that are transmitted by close contact and generally travel only short distances (up to 3 ft) from infected patients who are coughing or sneezing.

Gowns and protective apparel
Various types of gowns and protective apparel are worn to provide barrier protection and to reduce opportunities for transmission of germs in hospitals. Gowns are worn to prevent contamination of clothing and to protect the skin of staff from blood and body fluid exposures. Gowns especially treated to make them impermeable to liquids, leg coverings, boots, or shoe covers provide greater protection to the skin when splashes or large quantities of infective material are present or anticipated. Gowns are also worn by staff during the care of patients infected with certain germs to reduce the opportunity for transmission of disease causing germs from patients or items in their environment to other patients or environments; when gowns are worn for this purpose, they are removed before leaving the patient's environment and hands are washed.

Patient-care equipment and articles
Some used articles are enclosed in containers or bags to prevent inadvertent exposures to patients, staff, and visitors and to prevent contamination of the environment. Used sharps are placed in puncture-resistant containers; other articles are placed in a bag.
Contaminated, reusable critical equipment/devices or semi-critical equipment/devices are sterilized after use to reduce the risk of transmission of germs to other patients. (See the section on Sterilization)
Non-critical equipment contaminated with blood, body fluids, secretions, or excretions is cleaned and disinfected after use. Contaminated disposable (single-use) patient-care equipment is handled and transported in a manner that reduces the risk of transmission of germs and decreases environmental contamination in the hospital.

Linen and laundry
Although soiled linen may be contaminated with disease causing germs, the risk of disease transmission is negligible if it is handled, transported, and laundered in a manner that avoids transfer of germs to patients, staff, and environments.

Dishes, glasses, cups, and eating utensils
No special precautions are needed for dishes, glasses, cups, or eating utensils, disposable or reusable dishes and utensils can be used for patients on isolation precautions. The combination of hot water and detergents used in hospital dishwashers is sufficient to decontaminate dishes, glasses, cups, and eating utensils.
Routine and terminal cleaning
The room, or cubicle, and bedside equipment of patients on Transmission-Based Precautions are cleaned using the same procedures used for patients on Standard Precautions, unless the infecting germ(s) and the amount of environmental contamination indicates special cleaning. In addition to thorough cleaning, adequate disinfection of bedside equipment and environmental surfaces (e.g., bedrails, bedside tables, carts, commodes, doorknobs, faucet handles) is indicated for certain germs, which can survive for prolonged periods of time. Patients admitted to hospital rooms that previously were occupied by patients infected with such germs are at increased risk of infection from contaminated environmental surfaces and bedside equipment if they have not been cleaned and disinfected adequately.

Adapted from: Guideline for Isolation Precautions in Hospitals.
Julia S. Garner, RN, MN, and the Hospital Infection Control Practices Advisory Committee. From the Public Health Service, US Department of Health and Human Services, Centers for Disease Control and Prevention, Atlanta, Georgia. Garner JS, Hospital Infection Control Practices Advisory Committee. Guideline for isolation precautions in hospitals. Infect Control Hosp Epidemiol 1996; 17:53-80, and Am J Infect Control 1996; 24:24-52.
Asepsis
One of the methods for breaking the chain of infection is asepsis. Asepsis is defined as “a condition in which infectious agents are absent or controlled”. Aseptic practices break the chain of infection by preventing the transmission of infectious agents.
There are three levels of aseptic control:
· Antisepsis or sanitation
· Disinfection
· Sterilization
Antisepsis/sanitation method of infection control includes using soap and water to wash the hands and body as well as the use of antiseptics such as alcohol, iodine and betadine to clean the skin for medical procedures, as these inhibit the growth of infectious agents. This level of asepsis may kill or inhibit some organisms but is generally not effective against viruses and spores.
Disinfection is the process of using chemical agents or boiling water to destroy or kill disease causing germs. These chemical agents are not always effective against viruses and spores. Further, disinfectants are often harsh and may irritate or damage the skin so they are mainly used on surfaces, equipment and instruments. Common disinfectants include Clorox bleach solutions, Lysol, and pinesol products.
Sterilization is the only level of asepsis that kills all microbes both pathogenic (disease causing) and nonpathogenic (non-disease causing). It is the method used by all health care facilities and includes a number of techniques as described earlier. Sterilization is mainly used on medical instruments and equipment, surgical dressings, gowns etc. See the next section for details.
Medical asepsis
Medical asepsis (or Clean Technique) maintains cleanliness to prevent the spread of germs and ensures that the environment is as free of germs as possible. Medical asepsis helps to contain infectious organisms and to maintain an environment free from contamination.

Activity
Ask students how medical asepsis could be achieved.
The techniques used to maintain medical asepsis include hand washing, gowning and wearing facial masks when appropriate, as well as separating clean from contaminated or potentially contaminated materials and providing information to patients about basic hygienic practices. Appropriate hand washing by the nurse and the patient remains the most important factor in preventing the spread of microorganisms.
The basic principles of medical asepsis are:
i. Wash hands frequently, but especially before handling foods, before eating, after using a tissue paper, after going to the toilet, before and after each patient contact, and after removing gloves
ii. Keep soiled items and equipment from touching the clothing
iii. Do not place soiled bed linen or any other items onto the floor
iv. Avoid having patient’s cough, sneeze, or breath directly on others
v. Move equipment away from you when brushing, dusting, or scrubbing articles
vi. Avoid raising dust
vii. Clean the least soiled areas first then more soiled ones
viii. Dispose of soiled or used items directly into appropriate containers
ix. Pour liquids that are to be discarded directly into the drain so as to avoid splattering in the sink and onto you
x. Avoid leaning against sinks, supplies or equipment
xi. Avoid touching your eyes, face, nose or mouth
xii. Use practices of personal grooming that help prevent spreading germs
Surgical asepsis
Surgical asepsis (or Sterile Technique) includes procedures used to eliminate all microorganisms from an object or area. Surgical asepsis requires more stringent techniques than medical asepsis. An object or area is described as being sterile or not sterile.
Activity
Ask students how surgical asepsis could be achieved.
Ask students where surgical asepsis is practiced.
The basic principles of surgical asepsis include:
i. Only a sterile object can touch another sterile object
ii. Open sterile packages so that the first edge of the wrapper is directed away from the worker to avoid the possibility of a sterile wrapper touching unsterile clothing
iii. Avoiding spilling any solution on a cloth or paper used as a field for a sterile set-up
iv. Hold sterile objects above the level of the waist
v. Avoid talking, coughing, sneezing, or reaching over a sterile field or object
vi. Never walk away from or turn your back on a sterile field
vii. All items brought into contact with broken skin or used to penetrate the skin in order to inject substances into the body, or to enter normally sterile body cavities, should be sterile
viii. Use dry, sterile forceps when necessary
ix. Consider the edge (outer 1 inch) of a sterile field to be contaminated
x. Consider an object contaminated if you have any doubt as to its sterility
Surgical Asepsis is used in the operating room, delivery room, during surgical procedures, catheterization, and during dressing changes.
Sterilisation
Sterilization is the complete destruction of all living organisms including bacteria, viruses, spores and fungi, achieved by various methods.
There are two types of sterilization:
a) physical sterilization
i) heat (steam; dry heat)
ii) radiation
iii) filtration
b) chemical sterilization
i) ethylene oxide
ii) ozone
iii) chlorine bleach
iv) glutaraldehyde and formaldehyde
vi) hydrogen peroxide
Physical sterilisation
Heat
A widely-used method for steam sterilization is the autoclave. Autoclaves commonly use steam heated to 121 °C or 134 °C. To achieve sterility, a holding time of at least 15 minutes is required. Additional sterilizing time is usually required for liquids and instruments packed in layers of cloth, as they may take longer to reach the required temperature. After sterilization, autoclaved liquids must be cooled slowly to avoid boiling over when the pressure is released.
To ensure the autoclaving process was able to cause sterilization, most autoclaves have meters and charts that record or display information such as temperature and pressure as a function of time. Indicator tape is often placed on packages of products prior to autoclaving. A chemical in the tape will change color when the appropriate conditions have been met. Some types of packaging have built-in indicators on them.
For effective sterilization, steam needs to penetrate the autoclave load uniformly, so an autoclave must not be overcrowded, and the lids of bottles and containers must be left ajar. During the initial heating of the chamber, residual air must be removed. Indicators should be placed in the most difficult places for the steam to reach to ensure that steam actually penetrates there.
For autoclaving, as for all disinfection or sterilization methods, cleaning is critical. Cleaning can removes a large number of organisms. Proper cleaning can be achieved by physical scrubbing. This should be done with detergent and warm water to get the best results. Cleaning instruments or utensils with organic matter, cool water must be used because warm or hot water may cause organic debris to coagulate.
Autoclaving/Steam under Pressure
Most common sterilization by moist heat requires steam under pressure at temperature range of 121-1340C usually given in an autoclave.
Sterilization by steam autoclave (saturated steam under pressure of approximately 15 psi to achieve a chamber temperature of at least 250oF for a designated time) is the preferred and most convenient method to rapidly destroy all forms of microbial life. Steam autoclaves are used to sterilize glassware, instruments, gloves, liquids in bottles, biological waste, dressings, and other materials needing such treatment. However, to do this, material to be sterilized must come into contact with live steam. Bags or containers should be left open during autoclaving or water (~200ml) should be added to sealed bags to generate steam.
Principles
Moist sterilization requires that the steam used for sterilization must be both dry and saturated. Saturated in the sense that the steam in this context is at a phase where it is holding all the water that it can, in the form of transparent vapors. It does not contain water droplets and therefore it describe as being dry; if it meets an object cooler than itself it condenses.
Moist heat sterilization i.e. Autoclaving is performed in an autoclave. The most common conditions for sterilization under pressure Include:
Process
Temperature 0c
Holding Time(Min) for Sterilization
Pressure in PSI (Pounds Per Square Inch)
Moist Heat
121
126
134
15
10
3
15
20
30

Proper autoclave treatment will inactivate all fungi, bacteria, viruses and also bacterial spores.
Figure2: Autoclaves
Figure 3: Steam Autoclave
Moist Heat Sterilization: Moist heat sterilization is the most efficient bio-cidal agent. It is used for:
• Surgical dressings
• Sheets
• Surgical and diagnostic equipment
• Containers
• Closures
• Aqueous injections
• Ophthalmic preparations
• Irrigation fluids
Dry heat can be used to sterilize items, but as the heat takes much longer to be transferred to the organism, both the time and the temperature must usually be increased, unless forced ventilation of the hot air is used. The standard setting for a hot air oven is at least two hours at 160 °C (320 °F). A rapid method heats air to 190 °C (374 °F) for 6 minutes for unwrapped objects and 12 minutes for wrapped objects. Dry heat has the advantage that it can be used on powders and other heat-stable items that are adversely affected by steam (for instance, it does not cause rusting of steel objects).
Radiation
Methods exist to sterilize using radiation such as electron beams, X-rays, gamma rays, or subatomic particles.
Gamma rays are very penetrating and are commonly used for sterilization of disposable medical equipment, such as syringes, needles, cannulas and IV sets. Gamma radiation requires bulky shielding for the safety of the operators; they also require storage of a radioisotope, which continuously emits gamma rays (it cannot be turned off, and therefore always presents a hazard in the area of the facility).
Electron beam processing is also commonly used for medical device sterilization. Electron beams use an on-off technology and provide a much higher dosing rate than gamma or x-rays. Due to the higher dose rate, less exposure time is needed. A limitation is that electron beams are less penetrating than either gamma or x-rays.
X-rays are less penetrating than gamma rays and tend to require longer exposure times, but require less shielding, and are generated by an X-ray machine that can be turned off for servicing and when not in use.
Ultraviolet (UV) light irradiation is useful only for sterilization of surfaces and some transparent objects.
Subatomic particles may be more or less penetrating, and may be generated by a radioisotope or a device, depending upon the type of particle.
Filtration
Clear liquids that would be damaged by heat, irradiation or chemical sterilization can be sterilized by mechanical filtration. This method is commonly used for sensitive pharmaceuticals. A filter with pore size 0.2 µm will effectively remove bacteria. If viruses must also be removed, a much smaller pore size is needed. Solutions filter slowly through membranes.
Chemical sterilisation
Chemicals are also used for sterilization. Although heating provides the most reliable way to rid objects of all transmissible agents, it is not always appropriate, because it will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics.
Ethylene oxide (EO or EtO) gas is the most common sterilization method, used for over 70% of total sterilizations, and for 50% of all disposable medical devices; it is commonly used to sterilize objects sensitive to temperatures greater than 60 °C such as plastics, optics and electrics. Ethylene oxide treatment is generally carried out between 30 °C and 60 °C for at least three hours. It is used to process sensitive instruments which cannot be adequately sterilized by other methods. It can kill all known viruses, bacteria and fungi, including bacterial spores and is satisfactory for most medical materials, even with repeated use. However it is highly flammable, and requires a longer time to sterilize than any heat treatment.
Ozone is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. It has the benefit of being able to oxidize most organic matter. On the other hand, it is a toxic and unstable gas that must be produced on-site, so it is not practical to use in many settings.
Chlorine bleach is another accepted liquid sterilizing agent. Household bleach consists of 5.25% sodium hypochlorite. It is usually diluted to 1/10 immediately before use; however to kill Mycobacterium tuberculosis (organism that causes tuberculosis) it should be diluted only 1/5. Bleach will kill many organisms immediately, but for full sterilization it should be allowed to react for 20 minutes. It is highly corrosive and may corrode even stainless steel surgical instruments.
Glutaraldehyde and formaldehyde solutions (also used as fixatives) are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long. To kill all organisms can take up to 12 hours with glutaraldehyde and even longer with formaldehyde.
Hydrogen peroxide is another chemical sterilizing agent. It is relatively non-toxic once diluted to low concentrations and leaves no residue.
The following table gives the 4 levels of Processing/Reprocessing for already used medical equipment/devices for re-use. This is called the reprocessing of used medical equipment/devices.

The four levels are:
· Cleaning
· Low level disinfection
· High level disinfection
· Sterilization

Activity
Brainstorm what types of equipment/devices would need which of the four levels of Processing/Reprocessing.
Table: Reprocessing Decision Chart
Level of
Processing/Reprocessing

Classification of
Equipment/ Device

Examples of Equipment/Devices

Products to Use**

1. Cleaning
Physical removal of soil, dust or foreign material. Chemical, thermal or mechanical aids may be used.
Cleaning usually involves soap and water, detergents or enzymatic cleaners. Thorough cleaning is required before disinfection or sterilization may take place.
All reusable
equipment/devices

· Oxygen tanks and cylinders

• Quarternary ammonium
compounds (QUATs)
• Enzymatic cleaners
• Soap and water
• Detergents
• 0.5% Accelerated
hydrogen peroxide

2. Low level disinfection
Level of disinfection required when processing non-critical
Equipment/devices or some environmental surfaces.
Low level disinfectants kill most bacteria and some fungi as well as viruses. Low level disinfectants do not kill mycobacteria or bacterial spores.

Non-critical equipment/devices

(Medical equipment/device that either touches only intact skin but not mucous membranes [inner lining of the eyes, nose, and mouth] or does not directly touch the patient. Reprocessing of non-critical equipment/devices involves cleaning and may also require low level disinfection)

• Environmental surfaces touched by staff during procedures (e.g. dialysis machines)
• Bedpans, urinals, commodes
• Stethoscopes
• Blood pressure cuffs
• Glucose meters
• Electronic thermometers
• ECG machines/leads/
• Ultrasound
equipment/probes that come into contact with intact skin only
• Bladder scanners
• Baby scales
• Environmental surfaces (e.g. IV poles, wheelchairs, beds, call bells)
• 3% Hydrogen peroxide
(10 minutes)
• 60-95% Alcohol (10
minutes)
• Hypochlorite (1000 ppm)
• 0.5% Accelerated
hydrogen peroxide (5
minutes)
• Quarternary ammonium
compounds
• Iodophors
• Phenolics ** (should not be used in nurseries)

3. High level disinfection
The level of disinfection required when processing semi-critical equipment/devices.
High level disinfection processes destroy bacteria, mycobacteria,
Fungi and viruses, but not necessarily bacterial spores.

Semi-critical equipment/devices

(Medical equipment/device that comes in contact with non-intact skin or mucous membranes but ordinarily does not penetrate them.)


• Flexible endoscopes that do not enter sterile cavities or tissues
• Laryngoscopes
• Bronchoscopes (sterilization is
preferred)
• Respiratory therapy equipment
• Nebulizer cups
• Anesthesia equipment
• Endotrachial tubes
• Specula (nasal, anal, vaginal – disposable equipment is strongly
recommended)
• Ear syringe nozzles
• Ultrasound
equipment/probes that come into
contact with mucous membranes
or non-intact skin (e.g. transrectal
probes)
• Pessary and diaphragm fitting
rings
• Cervical caps
• Breast pump accessories
• Glass thermometers
• Ear cleaning equipment
• 2% Glutaraldehyde (20 minutes at 20°C)
• 6% Hydrogen peroxide (30 minutes)
• 0.55% Orthophthalaldehyde
(OPA) (10 minutes at 20°C)
• Pasteurization (30
minutes at 75°C)
• 7% Accelerated hydrogen peroxide (20 minutes)
• 0.2% Peracetic acid (30 - 45 minutes)


4. Sterilization
The level of reprocessing required when processing critical equipment/devices. Sterilization results in the destruction of all forms of microbial life including bacteria, viruses, spores and fungi.

Critical equipment/devices

(Medical equipment/devices that enter sterile tissues, including the vascular system. Critical medical equipment/devices present a high risk of infection if the equipment/device is contaminated with any microorganisms.)


• Surgical instruments
• Implantable equipment/devices
• Endoscopes that enter sterile
cavities and spaces (e.g. arthroscopes, laparoscopes,
cystoscopes)
• Bronchoscopes
• Colposcopy equipment
• Endocervical curettes
• Fish hook cutters
• Biopsy forceps, brushes and
biopsy equipment associated
with endoscopy (disposable
equipment is strongly
recommended)
• Eye equipment including soft
contact lenses
• Dental equipment including high speed dental hand pieces
• Dry heat
• 100% Ethylene oxide
• Formaldehyde
• 2.5-3.5% Glutaraldehyde
(10 hours at 20°C)
• Hydrogen peroxide gas plasma (75 minutes at 50°C)
• 6-25% Hydrogen peroxide liquid (6 hours)
• 7% Accelerated hydrogen peroxide (6 hours at 20°C)
• 0.2% Peracetic acid (30-45 minutes)
• Steam
• Ozone


** concentration and contact time are dependent on manufacturer’s instructions

Safe disposal of sharp instruments
Activity
Brainstorm the need for safe disposal of sharp instruments.
Healthcare workers often report injuries by sharp instruments. It is, therefore, essential to prevent these avoidable and potentially serious injuries. It is the responsibility of the staff using sharp instruments to dispose them safely in designated containers to prevent accidentally inoculating oneself with blood/body fluids.
Figure 4: Sharp disposal unit
Figure 5: Sharp disposal unit
All healthcare workers must observe the following:
Items to be discarded in a sharps container
· Needles, lancets, scalpel blades
· Syringes
· Glass vials, broken glass, slides
· Biopsy needles
· Disposable razors
· IV sets, cannulae
· Other disposable sharps
Location of sharps containers
The provision of sharps containers is essential for safe practice. Sharps containers should be available in the following areas:
· Treatment rooms
· Nursing bases
· Any area where sharps are used: small portable boxes must be available to take to patient’s bedside.
Disposal of needles/syringes
· Always dispose of sharps immediately after use
· Do not re-sheathe needles
· Needles and syringes must be discarded entire into sharps containers. They must not be disassembled by hand. Do not break or bend needles.
Removal of sharps containers
Many sharp injuries occur because of overfilling of disposal containers.
· Sharps containers should be of adequate capacity for the area where they are used
· The sharps containers should be discarded when they are ¾ full or weekly. They should be labeled with ward/department of origin and dated
· Do not overfill sharps containers
· Always ensure that containers are securely closed for removal
· Wards/departments must formalize arrangements for the removal of sharps containers
· Designated staff should be responsible for removing the containers and providing replacements
· Staff who remove sharps containers must wear suitable protective gloves
Adapted from Dudley Primary Care Trust, National Health Service, United Kingdom
Class room evaluation

Student: _________________________ ID: __________________________

Teacher: _________________________ Unit 7: Sterilization

Date: ________________________


Select the best response for each test item.

How would you describe personal hygiene?
________________________________________________________________________________________________________________________________________________________________________________________________________________________


What are the three times when hands should be washed?
a. ______________________________________________________________________
b. ______________________________________________________________________
c_______________________________________________________________________


What are the four steps of proper hand washing?
a. _______________________________
b. _______________________________
c. _______________________________
d. _______________________________

What are the three different kinds of hazards in the workplace?
a. _______________________________
b. _______________________________
c. _______________________________

What are the different types of common pathogens that cause diseases? Give two examples of each.
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________The chain of infection is a circle of ____________ links.

Nosocomial infections are infections which are a result of treatment in a _______________ or other __________________ facility.

The five main routes of transmission of infections are:
a. ________________________________________
b. ________________________________________
c. ________________________________________
d. ________________________________________
e. ________________________________________


Describe Universal precautions.
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


The three levels of aseptic control are:
a. _______________________________
b. _______________________________
c. _______________________________


Sterilization is described as:
____________________________________________________________________________________________________________________________________________________________


There are__________ types of sterilization (choose one from the following)
a. two
b. three
c. four
Give 10 examples of items which should be discarded in a sharps container.
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Notes

Notes