Infection Control Flashcards
Pathogenicity :
the ability to cause disease
Virulence
the degree of pathogenicity
Nonspecific Defense Mechanisms:
defense that protect us from any pathogen
Specific Defense Mechanism (immune response) :
defense that the body offers against a particular pathogen
Flora
Microorganisms that occur in specific environments such as: the intestine, skin , vagina and oral cavity
Two types of flora
Resident or normal Flora-always present
Transient flora- occur in periods of limited duration-e.g. Staph aureus
Six Links in the chain of infection
Infectious or causative agent Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host
Infectious /Causitive Agent:
1st link in chain of infection
An pathogen or disease producing micro-organism that invades the host and causes disease
Biological agent- living organism invade the host
Other agents
Chemical agent-substance that interact with the body e.g. pesticides, food additives, medications and industrial chemicals
Physical agent- environmental factors such as heat, light, noise and radiation
The Reservoir
2nd link in chain of infection
Place where the agent can survive , grow and multiply e.g. humans , animals and environmental surfaces
The reservoir must contain oxygen and organic matter in order for the host to grow
Must have proper temperature, Ph level, light and moisture for growth
Most common reservoirs are human, animals, the environment
Fomites - objects such as surgical instrument and laboratory instruments
Humans can be carriers or infectious agents
Human reservoirs.
Many common infectious diseases have human reservoirs.
Diseases that are transmitted from person to person without intermediaries include the sexually transmitted diseases, measles, mumps, streptococcal infection, and many respiratory pathogens.
Asymptomatic or passive or healthy carriers:
Human reservoir
never experience symptoms despite being infected.
Incubatory carriers:
Human reservoir
can transmit the agent during the incubation period before clinical illness begins.
Convalescent carriers :
Human reservoir
those who have recovered from their illness but remain capable of transmitting to others.
Chronic carriers
Human reservoir
are those who continue to harbor a pathogen such as hepatitis B virus
Animal reservoirs.
Humans are also subject to diseases that have animal reservoirs.
Diseases are transmitted from animal to animal, with humans as incidental hosts.
Example : brucellosis (cows and pigs), anthrax (sheep), plague (rodents), trichinellosis/trichinosis (swine), tularemia (rabbits), and rabies (bats, raccoons, dogs, and other mammals),West Nile encephalitis (birds)
Environmental reservoirs
Plants, soil, and water in the environment are also reservoirs for some infectious agents.
Many fungal agents, such as those that cause histoplasmosis, live and multiply in the soil.
Outbreaks of Legionnaires disease are often traced to water supplies in cooling towers and evaporative condensers, reservoirs for the causative organismLegionella pneumophila
Port of Exit
The path by which a pathogen leaves its host.
The portal of exit usually corresponds to the site where the pathogen is localized. For example:
Influenza viruses andMycobacterium tuberculosis: exit the respiratory tract, schistosomes through urine, cholera vibrios in feces
Blood borne agents: can exit by crossing the placenta from mother to fetus (rubella, syphilis, toxoplasmosis)
Blood borne Pathogens: others exit through cuts or needles in the skin (hepatitis B) or blood-sucking arthropods (malaria).
Modes of Transmission
An infectious agent may be transmitted from its natural reservoir to a susceptible host in different ways
Direct transmission-
Direct contact
Droplet spread
Indirect transmission-
Airborne
Vehicleborne
Vectorborne (mechanical or biologic)
Contact transmission-
Mode of Transmission- Direct
transfer of an agent from an infected person to a non infected person e.g. colds, Std’st
Occurs through skin-to-skin contact, kissing, and sexual intercourse.
Most frequent source of health care associated infections e.g. phlebotomist not changing gloves and washing hands before taking blood from the next patient
Droplet Transmission
Mode of Transmission- Direct
Form of contact but method of transfer is different (droplets propelled up to 3 feet- not suspended in the air)
Enters susceptible host trough the nasal mucosa, the mouth or conjunctiva of the eye
Example : Pertussis , influenza and meningococcal infection
Technician handling blood or body fluid
Airborne Transmission-
Mode of Transmission-Indirect
When a susceptible person contacts contaminated droplets or dust particles in the air e.g measles and anthrax spores(Particles distributed by air current)
Aerosols- created when removing
caps from tubes of blood, urine or other body fluid
Vehicle Transmission-
Mode of Transmission-Indirect
agent transferred by inanimate objects e.g. water , food , drugs and equipment
The inanimate object becomes a vehicle when it is touched or injected by a susceptible host
Technician: soiled lab coats must be disposed of properly
Soiled lab equipment must be disinfected
Vectorborne transmission-
Mode of Transmission-Indirect
Occurs when a living host e.g. mosquitoes, fleas, ticks, lice and other animals comes in contact with contaminated items, food, linen–
The animal or insect becomes the vector that transmits disease to the susceptible host. e.g Lyme disease (bite of deer ticks)
Portal of Entry
Blood (hepatitis B, human immunodeficiency virus)
Respiratory tract-
Portal of Entry
mucus droplets
Transplacental
Portal of Entry
from mother to foetus via the placenta or umbilical cord
Circulatory system
Portal of Entry
through insect or rodent bites
GI tract(orifices)-
Portal of Entry
ingestion of contaminated food or water
Genitourinary tract-
Portal of Entry
through contact with vaginal secretion or semen
Circulatory system
Portal of Entry
through insect or rodent bites
Integumentary system-
Portal of Entry
break in skin or mucus membrane
Susceptible host:
a person who lacks resistance and is vulnerable to disease
Compromised host
a person whose normal defence mechanisms are impaired and is more susceptible to infection
Staphylococci
Common Bacteria
wound, respiratory and gastro-intestinal infections
Eshericia coli
Common Bacteria
wound and urinary tract infections
Salmonella
Common Bacteria
food poisoning
Streptococci
Common Bacteria
wound, throat and urinary tract infections
Proteus
Common Bacteria
wound and urinary tract infections
Hepatitis A
Common Viruses
infectious hepatitis
Hepatitis B
Common Viruses
serum hepatitis
Hepatitis C
Common Viruses
blood exposure
Human immunodeficiency virus [HIV] -
Common Viruses
acquired immunodeficiency syndrome [AIDS]
Influenza
Common Viruses
the flu
Breaking the Chain of Infection
Lab technicians and health care workers must focus on breaking the chain of infection by applying proper infection control practices
Wear gloves when handling and obtaining specimens
Hand Washing- Frequently and after changing gloves
Disinfection and sterilization
Cover all cuts and abrasions
Cough Etiquette
No recapping of needles
Proper disposal of contamination items
Follow isolation precaution when required
Hand washing
Standard Precautions
Wash hand immediately after removing gloves and between patient contact
Wash hands after touching blood and body fluid , regardless if gloves are worn
Use soap and wash for minimum 10-15 seconds
Can use alcohol based hand rubs when no visible dirt
Gloves
Standard Precautions/PPE Does not replace handwashing Clean, sterile or non sterile Resistant to tear and puncture proof Non-latex, vinyl, or nitril Wear gloves when handling blood and body fluids Remove gloves after use and wash hands
Mask
Standard Precaution/PPE
Example: NIOSH certified N95 respirators/masks are designed to help provide respiratory protection for the wearer.
The N95 respirator/mask has a filter efficiency level of 95% or more against particulate aerosols free of oil when tested against a 0.3 micron particle.
It is fluid resistant, disposable and may be worn in surgery.
The “N” means “Not resistant to oil”. The “95” refers to a 95% filter efficiency.
N95 respirator/mask with an exhalation valve may be used by the Health Care Worker.
Fully cover nose and mouth
Needle Safety
Needlestick and other sharps injuries are a serious hazard in any healthcare setting.
Contact with contaminated needles, broken glass, and other sharps may expose healthcare workers to contaminated blood
One hand needle covering device- safety-engineered needle
Never break off, recap or re-use needles
Dispose needles in a puncture resistant container
Needlestick or sharps injury
Immediately follow these steps: Wash needlesticks and cuts with soap and water. Cover with sterile tape Report the incident to your supervisor Immediately seek medical treatment.
Normal Defence MechanismsNon-specific
The immune system serves as our normal defence against transmission of infectious agents Non-specific immune defence-protective response does not dependent on prior exposure Fights pathogens in the same way every time the pathogen comes in the body Example: the skin and normal flora-physical (external) barrier Mucous membrane (external barrier) -entraps infectious agents and contain antibodies which inhibits bacterial growth
Lines of Defense
- First Line of defense: Skin, mucous membrane and secretions
- Second Line of defense: Phagocytic white blood cell Inflammation and fever
- Third Line of Defense: Specialized lymphocytes : B cells and T cells
- Antibodies form
Specific Immunity
Normal Defence Mechanisms
Specific Immune Defence respond to a specific invading antigen (antigen presenting cell)
Requires to prior exposure to a pathogen in order to work
At the first exposure – immune system recognizes the pathogen as being foreign, reacts to it and then remembers it
Specific Immunity- B Cells
Humoral response
B-cells makes antibody to attack a foreign antigen
Do not attack antigens directly
Respond to antigens (under the direction of T cells)
Clone itself to form plasma cells or memory B cells
Specific Cell Mediated Immunity-T cells
Recognize …react…remember
When phagocytes cannot completely destroy the antigen presenting cell T-lymphocytes( t-cells) are produced which binds to the antigen and destroys it
T-cells- regulates the immune response by producing cytokines called lymphokines that attract lymphocytes and phagocytes to assist in antigen destruction
T-Cells –that have a receptor for the antigen recognizes and binds to the antigen. Once bound T cells are activated and begin to divide into 3 T cell types
Cytotoxic T cells
Looks for cells with a specific foreign antigen.
Protecting the body against viruses and cancer cells
Helper T cells
Increase antibody formation, memory cell formation, B-cell formation, and neutrophils and macrophages to clean up
Memory T cells
“Remember” the pathogen that activated the original T cell… response is faster and stronger
humoral immunity
T Cells -stimulate the production of B- lymphocytes which differentiate into plasma cells producing antibody specific to the antigen
acquired immunity
B-cell activation forms memory cells
Memory cells remember the antigen and prepare the host for future antigen invasion
Natural Active Acquired Immunity-
body recognizes the specific antigen as foreign , produces antibodies or activates T –cytotoxic cells to destroys the pathogen
-Make antibodies and memory cells
-Long lasting
The body remembers the specific antigen
e.g. having had and recovered from the disease e.g. Measles
Natural Passive Acquired Immunity-
The body acquire specific immunity through natural means from someone
Short-lived
e.g Antibody pass from mother to baby through the placenta or breast milk
Artificial acquired Active Immunity-
the body acquires a pathogen in an artificial way then develops its own humoral or cellular immunity
Make antibodies and memory cells
Long lasting
e.g weakened antigen( vaccination ) introduced into the body to form antibody. e.g. Smallpox virus and MMR
Artificial acquired Passive
Immunity-when an individual receives an injection of serum containing antibodies from another person or animal.
- No antibody and memory cell production
- The effect is temporary
e.g RhoGAM to prevent Rh hemolytic disease of newborns
Immunization-
increase ones resistance to an infection. Substance injected stimulates production of antibodies e.g. flu shot
Recognition phase of Immune Response
1st phase
Antibodies or Immunoglobulins (Proteins) that are made in response to an antigen and can recognize and bind to that antigen
Activation phase of Immune Response
2nd phase
Antigen selects a specific pre-existing clone of lymphocyte and activates it.
Effector phase of Immune Response
3rd phase
B lymphocytes differentiate in long memory cells and plasma cells-inactivated antigen by binding to it.
Helper T lymphocytes-stimulate other T and B cells of the immune system to fight intruders
Killer(cyto-toxic)T cells -destroys viruses and cancer cells on contact
Nosocomial (Hospital Acquired) Infections
Infection that is acquired in the hospital
Health care workers can pass along infection
Failure to follow proper hand washing techniques
Nosocomial pathogens include bacteria, viruses and fungal parasites.
Most common infections involve the urinary tract (catheter ) , upper and lower respiratory tract (ventilators) , surgical site and central lines associated bloodstream infections
Nosocomial (Hospital Acquired) Infections- PREVENTION
Nosocomial infections are often caused by breaches of infection control practices and procedures, unclean and non-sterile environmental surfaces, and/or ill hospital staff.
Prevention of nosocomial infections includes infection control programs, proper personal hygiene and hand washing on the part of the hospital staff, complete sterilization of medical equipment, and providing a clean, sanitary environment in the health care facilities
