infection control

Why is infection control important?

~ Hospitals are gathering places for the sick (potential to be centers for disease transmission).

~ Those with health problems are more susceptible to infections.

~ Health care workers have a professional duty to follow infection prevention policies 

Microorganisms

Microorganisms - Microscopic living organisms that live on or inside the body or other surface

• Can be acted on by gravity (can fall and accumulate on surfaces like the ground)

• Can grow in or on a host organism

• Normal Flora – microorganism that live on/in the body without causing harm

Microorganisms can be classified into five groups:

• Bacteria – single-celled organisms with a cell wall and an atypical nucleus that lacks a membrane (often treated with antibiotics)

  • Can grow independently and replicate without a host

  • Common bacterial infections: tuberculosis, strep throat, food poisoning

• Viruses – among smallest of known disease-causing organisms

  • Cannot survive independently or outside of a living cell

  • Common viral infections: HIV, hepatitis B, rhinovirus (common cold), varicella (chicken pox)

  • Fungi – can occur in two distinct forms: as single-celled yeasts or as long, branched, filament-like structures called molds that are composed of many cells

    • Cab be good – used to produce penicillin

    • Common fungal infections: athletes foot, ring worm, respiratory infections

  • Prions – smallest and least understood of all pathogens; believed to be infectious proteins

    • Resistant to the body’s natural defenses

    • Can continuously multiply if left unchecked, causing irreversible neurologic damage

    • Common prion infections: Mad cow disease

  • Protozoa – complex single-celled organisms that exist as free-living organisms; a few are parasitic and live within the human body

    • May be classified as motile or nonmotile

Pathogens

Pathogens are any microorganisms capable of causing disease.

They possess certain properties (virulence factors) that distinguish them from nonpathogenic organisms or normal flora:

• They can multiply in large numbers and cause an obstruction

• They can cause tissue damage -

  • Excrete protein substances called toxins that can kill or injury the host cell

    • Causes side effects such as fever, nausea, vomiting, shock

  • They can destroy red and white blood cells 

Cycle of Infection

There are 6 steps in the establishment of an infectious disease: (not in text)

1. Encounter – an infectious organism coming in contact with the host 

2. Entry – environment conducive to pathogen survival

3. Spread – pathogen must overcome the host’s immune defenses & then may be spread (ex. Viruses that cause common cold are easily spread through coughing and sneezing)

4. Multiplication – most pathogens must multiply for their impact to be recognized – this is called the incubation period

5. Damage – Damage can be either direct or indirect.

   • Direct damage - destruction of the host cell (toxins/poisons secreted by the infectious agents)

   • Indirect damage - infectious microbe altering the metabolism of the host

6. Outcome – An encounter with a pathogen can result in 1 of 3 outcomes

   • The host gains control of the infectious agent and eliminates it

   • The pathogen overcomes the host’s immunities to cause damage

   • The host and the infectious agent compromise and live in a state of mutual benefit

There are 5 factors involved in the spread of disease. For infections to be transmitted there must be:

1. Infectious Organism – there must be some sort of pathogen 

2. Reservoir of Infection – any place where pathogens can thrive in sufficient numbers to pose a threat (reservoirs may be humans, animals, soil, foods, or water)

3. Portal of Exit - route through with the pathogen can exit the reservoir 

   • Respiratory tract, GI tract, urinary tract, blood, body fluids, infected wounds

4. Susceptible Host – Often those patients with reduced natural resistance to infection

5. Portal of Entry – route by which pathogen can gain access into the susceptible host

   • Respiratory tract, upper GI tract, urinary tract, open wounds, mucous membranes (eyes, nose, mouth), bloodstream

Transmission of Diseases

Communicable Diseases – illnesses that can spread from person to person OR animal to a person 

There are 6 main routes of transmission:

1. Direct - host directly touches/comes in contact with the source infection or pathogen (ex. Kissing, touching, sexual intercourse)

Indirect

2. Fomites – an object that has been in contact with a pathogen and now harbors the pathogen (ex. Dirty linen, unwashed cassette, contaminated gloves)

3. Vectors – an insect or animal transfers the infection to another host (ex. ticks)

4. Vehicles – any medium that transports microorganisms (ex. Food, water, drugs, blood)

5. Droplet – contact of the mucous membranes of eyes, nose, or mouth with large droplets containing microorganisms (such as from someone coughing, sneezing, or speaking)

   • these are considered “large” droplets (over 5 microns) that do NOT remain suspended in the air & only travel short distances

6. Airborne – contact of the mucous membranes of eyes, nose, or mouth with large droplets containing microorganisms (such as from someone coughing, sneezing, or speaking); these droplets may also be inhaled by others

   • these are considered “small” droplets (under 5 microns) that remain suspended in the air for long periods of time & may be dispersed by air currents

Four Stages of Infectious Diseases (not in text)

We should always treat disease as if they are always highly infectious.

1. Latent Period – Stage when pathogenic microorganisms enter the body and lie dormant (no symptoms); some diseases are still contagious during this period (ex. Chicken pox)

2. Incubation Period – During this stage the microbe reproduces and the disease process begins

3. Active or Full Stage - All characteristic signs and symptoms are at their peak; disease is the most communicable

4. Convalescence Phase – Symptoms begin to diminish and eventually disappear, or, with some chronic infections, go into remission; some diseases may still be communicable

Body’s Defense Against Infection

There are 3 ways in which the body is protected from the invasion of microorganisms:

1. Natural Resistance – mechanical barriers such as intact skin and mucous membranes

   • Mucous membranes of secrete mucous to trap foreign particles

   • Respiratory tract is lined with cilia to transport contaminated mucous out

   • Chemicals in body fluids such as tears, stomach acids, vagina, and skin help destroy invading microorganisms

   • If microorganisms enter the body the second line of defense in an inflammatory process which increases blood flow to site and permits the passage of fluids and white blood cells to destroy the invading pathogens (process is phagocytosis)

2. Acquired Immunity – the state of being resistant to specific infections

   • Immunity after becoming infected with a specific microorganism or being injected with dead or weakened strains of microorganisms

   • Your body creates antibodies in response to specific antigens resulting in long term resistance

3. Passive Immunity – occurs after an injection of performed antibodies to a particular infection (ex. Receiving antibody treatments, babies receive antibodies from mothers and mother’s milk) 

   • Because the body does not produce these antibodies, passive immunity is short

Health Care -Associated Infections (HAIs)

Also called nosocomial infections or hospital-acquired infections are infections that occur more than 48 hours after being admitted to the hospital. These are infections acquired while receiving care in a health care setting for another condition.

• HAIs are one of the 10 leading causes of death in the U.S.

• Multidrug-Resistant Organisms (MDROs) - infections that are untreatable or difficult to treat because they are resistant to the more than one antibiotics

  • Methicillin-resistant Staphylococcus Aureus (MRSA)

  • Vancomycin-resistant enterococci (VRE)

  • Clostridium Difficile (C-Diff)

  • Overuse of antibiotics has allowed organisms to adapt - at first antibiotics kill most bacteria, but the longer antibiotics are used, the more likely the bacteria will become resistant

Iatrogenic Infections – those that result from an intervention with a physician only (ex. patient develops PNA after having a lung biopsy by a physician but what never admitted to hosptial)

Sources of Cross Infection – 

1. Medical Personnel 

   • Poor hand hygiene, direct contact, inhalation, ingestion (food handlers)

2. Patient Flora

   • Potentially harmful bacteria are harbored in the nasopharynx of almost every healthy person – flora does not cause harm if healthy, but if a patient is compromised it may cause harm

3. Contaminated Healthcare Environments 

   • Contaminated instruments

4. Bloodborne pathogens

   • Disease-causing microorganisms that may be present in the human blood

   • Transmitted through exposure to blood items contaminated with blood 

   • Examples – HIV, Hepatitis B, C, & D; syphilis

5. Invasive Procedures

   • allow microbes to gain easy entrance into the body

   • examples – urinary catheters, ventilators, central lines, surgical sites

Preventing Disease Transmission

Health care workers can protect themselves and others through the use of:

• Immunizations

• Boosters

• Post-exposure protocols

  • If an accidental needle stick occurs or skin is broken by contaminated object, allow the wound to bleed under cold water and wash with soap and water; inform charge tech and complete incident report

  • If your eyes, nose, or mouth are splashed with contaminated fluids or with body fluids, rinse these mucous membranes with copious amounts of water; inform charge tech and complete incident report

Centers for Disease Control and Prevention (CDC):

CDC is a US federal agency & leading national public health institute

• Main goal is to protect public health/safety by controlling/preventing disease, injury, & disability

• Improves health by developing control/prevention guidelines for infectious diseases, food borne pathogens, environmental health, occupational health/safety, & injury prevention

• Provides education & recommendations for safe practices

Standard Precautions– a system recommended by the CDC to reduce to risk of transmission of infections from unrecognized sources of bloodborne disease and from other pathogens in health care institutions (improves upon previous methods of universal and body substance precautions)

• Applies to blood, ANY body fluids, secretions/excretions, nonintact skin, mucous membranes or ANY items contaminated by these

• Also includes transmission-based precautions

Gloves – most common protection used in the imaging–worn for any contact with body fluids

Personal Protective Equipment (PPE)

• Provide a barrier between the patient and the health care worker

• Includes wearing gloves, fluid-repellent gowns, facemasks, protective eyewear, and utilizing resuscitation masks and bags when necessary

• Must wear when in contact with body fluids or ANY contaminated items

Medical Asepsis – Reduces the probability of infectious organisms being transmitted to a susceptible individual

Microbial dilution – process of reducing the number of organisms

• Hand hygiene (Review steps pg. 170-171)

• Disinfection – destruction of pathogens by using chemical materials

• Sterilization (Surgical Asepsis) – treating items to make them germ-free

Disinfection – the destruction of pathogens by using a chemical material

• When applied topically, may be called an antiseptic

• Bacteriostatic agent stops the growth of bacteria

• Bactericidal agent causes cell killing

• Common chemical disinfectants used in radiology departments:

  • Chlorine/Bleach, Hydrogen peroxide wipes, Skin preps (betadine, Chloraprep)

Hand Hygiene

• Washing hands for 30-60 seconds with soap & water

  • Done before AND after patient contact

  • Use hand washing instead of gel anytime hands are visibly soiled

  • Up to 7-8 minutes washing may be required 

• Alcohol-based rubs

  • More effective at killing some HAI organisms such as C. diff

  • More convenient than accessing sinks

  • Use before AND after patient contact as long as hands are not visibly soiled, before donning AND after removing gloves, after contact with objects in immediate vicinity of patient

Cleaning Techniques

• Clean from least contaminated to most (don’t contaminate yourself or clean areas)

• Clean all equipment that comes into contact with patient after each use

  • Be sure to clean lead aprons, machines (even the parts YOU touch when performing an exam), sponges, cassettes, etc.

  • Cover cassettes with protective bags to prevent contamination

  • Cassettes should be wiped with purple or gray top wipes ONLY (no green top wipes, they break down the cassettes)

• Allow disinfectants to remain wet for the minimum amount of time

• Replace linens after each patient

  • Contaminated linens all placed in linen bags/hampers

  • Fold edges to middle without shaking or flapping

  • Do not store clean and dirty linen in the same area

• Sharps containers used for proper disposal of needles

Disposable items – Red bagged

• Any items saturated or dripping with blood, blood products, body fluids that contain visible blood and body fluids

• Tubing contaminated with visible blood, suction canisters, drainage bags with visible blood, isolation equipment (if visibly soiled with blood)

Isolation Techniques – What precautions do we use for patients with communicable diseases to prevent the spread?

Disease-specific isolation – the epidemiology of each disease was considered individually

• Each communicable disease would have its own list of precautions to take

• These variations in precautions made it easy for staff to make mistakes in applying precautions

• Caused increased staff exposures in the case of delayed or misdiagnosis

Category-specific isolation (Transmission-based isolation) – diseases are grouped into categories based on routes of transmission

Airborne Precautions

• Reduces the risk of transmitting particles containing the infectious organism or airborne droplet nuclei (5 micrograms or smaller); can remain suspended in air for long periods of time; examples TB and measles

  • Patients in negative pressure rooms

  • Must wear N95 mask/PAPR & eye protections

  • Hand Hygiene

  • Patient must wear surgical mask when transporting out of room

Droplet Precautions

• Reduces the contact of large-particle droplets (greater than 5 micrograms) with or mucous membranes of the nose and mouth; these droplets can travel 3 feet; examples – pneumonia, influenza, diphtheria

  • Patients in private rooms

  • Must wear masks & eye protection

  • Hand hygiene

  • Patients must wear mask when transporting out of room

Contact Precautions

• Reduces the risk of transmitting pathogens by direct contact indirect contact with contaminated objects

  • Gloves & Gown

  • Hand hygiene

Protective Isolation (Reverse Isolation) 

• Designed to prevent the spread of infections to compromised patients (neonates, organ transplants, burn victims, chemotherapy patients)

  • Protective measures can range from additional hand hygiene to use of gown, gloves, masks – check signs on patient room/chart 

  • Wipe down all equipment PRIOR to entering the room, leave any unnecessary equipment outside the patient room 

  • When possible, use plastic bags to cover “high-touch” items you will be using on the patient (such as cassette and lead apron)

  • Try to have a “clean” tech that only touches the patient, and a “dirty” tech to handle the x-ray machine/equipment

  • Do not participate in these exams if you yourself are feeling ill

Radiography of Isolation Patients – Review steps on pates 178-182 (procedures 10.2 & 10.3)

• Requires 2 technologists (1 tech touches patient, 1 tech touches equipment)

• Reduces contamination of equipment which is difficult to disinfect completely

• When patient is in the department, use sheets to cover tables, wheelchairs, etc.

• Wear appropriate protective apparel

• Thoroughly clean all equipment used in isolation rooms OR with isolation patients 

  • Do not "cross contaminate” items

  • Ensure you wear appropriate PPE when cleaning contaminated items

  • Abide by “wet times” on cleaning wipes

Psychological Considerations of Isolation Protocols

• Isolation can lead to increased anxiety, depression, fear, frustration, loneliness, and anger

• Isolation can lead to decreased staff interaction with patients

  • This leads to feeling of “poor care”

  • Can lead to increase of adverse events

• Masks can cause anxiety/claustrophobia & PPE can look intimidating

• Ensure patients understand WHY isolation is important & “tune in” to a patient’s coping mechanisms and needs