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Flashcards in Infection Control Deck (71)
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1

Pathogenicity :

the ability to cause disease

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Virulence

the degree of pathogenicity

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Nonspecific Defense Mechanisms:

defense that protect us from any pathogen

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Specific Defense Mechanism (immune response) :

defense that the body offers against a particular pathogen

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Flora

Microorganisms that occur in specific environments such as: the intestine, skin , vagina and oral cavity

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Two types of flora

Resident or normal Flora-always present
Transient flora- occur in periods of limited duration-e.g. Staph aureus

7

Six Links in the chain of infection

Infectious or causative agent
Reservoir
Portal of exit
Mode of transmission
Portal of entry
Susceptible host

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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

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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

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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.

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Asymptomatic or passive or healthy carriers:

Human reservoir
never experience symptoms despite being infected.

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Incubatory carriers:

Human reservoir
can transmit the agent during the incubation period before clinical illness begins.

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Convalescent carriers :

Human reservoir
those who have recovered from their illness but remain capable of transmitting to others.

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Chronic carriers

Human reservoir
are those who continue to harbor a pathogen such as hepatitis B virus

15

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)

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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 organism Legionella pneumophila

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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 and Mycobacterium 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).

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Modes of Transmission

An infectious agent may be transmitted from its natural reservoir to a susceptible host in different ways

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Direct transmission-

Direct contact
Droplet spread

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Indirect transmission-

Airborne
Vehicleborne
Vectorborne (mechanical or biologic)

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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

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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

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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

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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

25

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)

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Portal of Entry

Blood (hepatitis B, human immunodeficiency virus)

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Respiratory tract-

Portal of Entry
mucus droplets

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Transplacental

Portal of Entry
from mother to foetus via the placenta or umbilical cord

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Circulatory system

Portal of Entry
through insect or rodent bites

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GI tract(orifices)-

Portal of Entry
ingestion of contaminated food or water

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Genitourinary tract-

Portal of Entry
through contact with vaginal secretion or semen

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Circulatory system

Portal of Entry
through insect or rodent bites

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Integumentary system-

Portal of Entry
break in skin or mucus membrane

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Susceptible host:

a person who lacks resistance and is vulnerable to disease

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Compromised host

a person whose normal defence mechanisms are impaired and is more susceptible to infection

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Staphylococci

Common Bacteria
wound, respiratory and gastro-intestinal infections

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Eshericia coli

Common Bacteria
wound and urinary tract infections

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Salmonella

Common Bacteria
food poisoning

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Streptococci

Common Bacteria
wound, throat and urinary tract infections

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Proteus

Common Bacteria
wound and urinary tract infections

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Hepatitis A

Common Viruses
infectious hepatitis

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Hepatitis B

Common Viruses
serum hepatitis

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Hepatitis C

Common Viruses
blood exposure

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Human immunodeficiency virus [HIV] -

Common Viruses
acquired immunodeficiency syndrome [AIDS]

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Influenza

Common Viruses
the flu

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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

47

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

48

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

49

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

50

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

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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.

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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

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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

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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

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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

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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

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Cytotoxic T cells

Looks for cells with a specific foreign antigen.
Protecting the body against viruses and cancer cells

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Helper T cells

Increase antibody formation, memory cell formation, B-cell formation, and neutrophils and macrophages to clean up

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Memory T cells

“Remember” the pathogen that activated the original T cell… response is faster and stronger

60

humoral immunity

T Cells -stimulate the production of B- lymphocytes which differentiate into plasma cells producing antibody specific to the antigen

61

acquired immunity

B-cell activation forms memory cells
Memory cells remember the antigen and prepare the host for future antigen invasion

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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

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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

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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

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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

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Immunization-

increase ones resistance to an infection. Substance injected stimulates production of antibodies e.g. flu shot

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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

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Activation phase of Immune Response

2nd phase
Antigen selects a specific pre-existing clone of lymphocyte and activates it.

69

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

70

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

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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