Infectious Disease Flashcards
What is a communicable disease?
An infectious disease that can be transmitted from one person to another
What are the public health principles of infectious and communicable disease? (4)
Epidemiology
Identification and investigation
- Index case
Prediction
Prevention
Who is Health Canada?
They are a federal department responsible for helping Canadian’s maintain and improve their health, while respecting individual choices and circumstances
What is body substance isolation? (2)
BSI supercedes universal precautions
It is based on the premise that all exposures to body fluids, under any circumstance, are potentially infectious
The development and/or manifestations of clinical disease depends on several factors. What are these factors? (4)
Virulence (degree of pathogenicity)
Number of infectious agents (dose)
Resistance (immune status) of the host
Correct mode of entry
What are the chain of elements for an infectious disease? (6)
The pathogenic agent
A reservoir
A port of exit from the reservoir
An environment conducive to transmission of the pathogenic agent
A portal of entry into the new host
Susceptibility of the new host to the infectious disease
What is a pathogenic agent?
A pathogen is a microorganism that can create pathological processes in the human host.
How are pathogenic agents classified? (4)
Morphology
Chemical composition
Growth requirements
Viability
What is normal flora? (2)
Organisms that live inside the body
They compete with invading pathogens
What are opportunistic pathogens?
Ordinarily non-harmful bacteria that cause disease under unusual conditions
What are spores?
The reproductive elements of the microorganism
What is germination?
The process where a spore begins to develop
What is the germination time?
The time from release of a pathogen until it infects another cell and causes the release of a new generation of particles
What is colonization?
A group of identical (clone) organisms derived from a single parent
What is contamination?
The soiling of an item by the introduction of organisms
What is a convalescent carrier?
An individual who is clinically recovered from an infectious disease but is still capable of transmitting the infectious agent to others
What is a chronic carrier?
An individual who does not display the symptoms of a disease, but harbours the pathogen which causes it, or has the gene (or genes) for it, and can transmit the disease to others either through interacting with other individuals, or by passing the disease-causing gene (or genes) to offspring
What is a nosocomial infection?
A hospital acquired infection
What is leukocytosis?
It is an abnormal elevation of WBC count
What is purulent exudate?
Pus filled discharge
What is epidemiology? (2)
The study of distribution and determinants of health related states and events in populations and the control of health problems.
It is the study of epidemic disease
What are the types of pathogenic agents? (6)
Bacteria Viruses Prions Fungi Protozoa Helminths
What is bacteria? (6)
Single cell organism
Require a host to supply food and a supportive environment
Self-reproducing without a host
Has no nucleic material
Produce toxins which are usually more toxic than the bacteria itself (endo or exotoxins)
Can cause local or systemic infection
What is an endotoxin?
Waste products released by living bacteria
What is an exotoxin?
Toxic products released when bacteria die or decompose
What is a gram positive test?
The cell wall is composed of a thick layer of peptidologlycan
What is a gram negative test?
The cell wall is composed of a thin layer of perptidologlycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxins
What are bactericidal antibiotics?
They are capable of killing bacteria
What are bacteriostatic antibiotics?
They inhibit bacterial growth and reproduction
What happens if a bacteria can alter cell membrane structure?
They develop resistance
What happens if antibiotics alter normal flora?
May lead to other complications
What is the lag phase in bacteria growth? (2)
Metabolism is adjusted to allow for a new cycle of growth
No increase in number, just an increase in size
What is the exponential phase or log phase of bacterial growth? (3)
Growing and dividing at maximum rate dependant on conditions
One cell gives two cells, and so on
Determinants of growth rate: different nutrients allow for different growth rates, temperature, pH, oxygen and other physical parameters and genetic determinants
What is the stationary stage of bacterial growth? (3)
It is a closed system - cells can’t grow indefinitely
No further net increase in cell number
Cells stop growing because: their energy is exhausted, toxic metabolites accumulate, pH changes, a necessary nutrient is depleted or a physical condition changes
What is the death phase of bacterial growth? (2)
Exponential decline in viable cell numbers
Can reverse this phase if modified the environmental parameters
What is a virus? (4)
It is anucleated living organisms that has genetic material (DNA/RNA) and they cannot reproduce by themselves
They may contain other microorganisms
Obligate intracellular parasites: they take over cell protein synthesis mechanism, they kill the host cell, they are difficult to distinguish as foreign
Infection is always pathological
How does a virus replicate? (4)
The virus attaches to the cell
RNA/DNA supplies the codes for building the protein coat and for producing certain enzymes needed to replicate more viruses
Also provides enzymes to lyse the cell which in turn totally ruptures the cells outer membrane, thus totally destroying the cell
This releases more of the virus into the system
Is the growth and reproduction of a virus affected by antibiotics?
No
What drug is required to disrupt the reproductive cycle of a virus?
Anti-viral
What is prion? (2)
The proteins are folded so that protease can’t act on them
They are incurable diseases
What is a fungi? (2)
Plant like
They are the common cause of vaginal infections
What is a protozoa? (2)
It is a single celled parasite with the ability to move
Malaria and gastroenteritis are examples
What are parasites? (2)
Organism that lives in or on another
Common cause of disease where sanitation is poor
What is a pinworm?
Tiny worms that live in the distal colon
What are hookworms?
They are passed in the stool of infected animals
What is trichinosis?
It is contracted by eating raw or inadequately cooked meat
What are the factors that affect a pathogens ability to create pathological processes? (4)
Its ability to invade and reproduce within a host and the mode in which it does so
Its speed of reproduction, ability to produce a toxin, and the extent of tissue damage that it causes
Its potency
Its ability to induce an immune response in the host
What is a reservoir?
It is the environment in which a pathogen lives and reproduces
What does the life cycle of an infectious agent depend on? (3)
The demographics of the host
Genetic factors
The efficacy of therapeutic interventions once infection has been established
What is the portal of exit?
The mechanism or method by which a pathogenic agent leaves one host to invade another involves a portal of exit?
What are some examples of a portal of exit? (6)
GU tract Intestinal tract Oral cavity Respiratory tract An open lesion Or any wound through which blood escapes
What is the portal of entry?
It refers to the means by which the pathogenic agent enters a new host
What is direct disease transmission?
It occurs when there is a physical contact between the source and the victim
What is an indirect disease transmission?
The organism survives on animate or inanimate objects for a period without a human host
What is host susceptibility?
It is influenced by a person’s immune response and by several other factors
What are some factors that effect host susceptibility? (6)
Human characteristics General health status Immune status Geographical and environmental conditions Cultural behaviours Sexual behaviours
What are some external barriers to the human response to infection? (5)
Flora: enhances the effectiveness of the surface barrier by competing for nutrients with the pathogen, maintains a pH suitable for itself an not the pathogen, if it is displaced to another area may act as a pathogen
Skin
GI system
Upper respiratory tract
Genitourinary tract
What are some internal barriers to the human response to infection?
They protect against pathogenic agents when the external lines of defence are breached. They include inflammatory and immune response
What is an inflammatory response?
It is the local reaction to a cellular injury
Why is an inflammatory response generally protective and beneficial?
It may initiate destruction of the body’s own tissue if the response is sustained or directed toward the host’s own antigens
What are the three separate stages inflammatory response may be divided into?
Cellular response to injury
Vascular response to injury
Phagocytosis
What is the backbone of the immune response?
White blood cells
What is the humoral immunity component? (2)
It is a time-consuming response
Specialized white blood cells (B-cells) eventually differentiate into antibodies
What is a cell-mediated immunity component? (2)
Time-consuming response
T-cells coordinate the activity of other components of the immune system to deal with foreign materal
What is the complement system of immune response? (2)
Part of the immune system that can recognize and kill invaders on first sight
Doesn’t take time to mobilize specialized responses like the humoral and cell-mediated components of white blood cells
What is the reticuloendothelial system (RES)?
It works in conjunction with the lymphatic system to dispose of the ‘garbage’ material that results from immune system attack of intruders
What is the reticuloendothelial system composed of? (6)
Composed of immune cells of the following: Spleen Lymph nodes Liver Bone marrow Lungs Intestines
What do reticuloendothelial system (RES) structures serve as?
They serve as sites where mature B and T-cells are stored until the immune system is activated by the presence of intruders
What are the stages of infectious disease? (4)
Latent period
Incubation period
Communicability period
Disease period
What is the latent period stage of infectious disease? (2)
A seemingly inactive period between the instant of exposure to the point the agent can be shed
It is considered non-contagious
What is the incubation period stage of infectious disease? (2)
The time from the moment of inoculation (exposure) to the development of the clinical manifestations of a particular infectious disease
First appearance of symptoms
What is the communicability period stage of infectious disease?
Begins at the end of the latent period and continues as long as the agent is present and can spread
What is the disease period stage of infectious disease? (3)
It follows the incubation period
Is variable depending on the disease
Process may resolve or if agent incorporates in a cell and becomes dormant or inactive it is considered to be in the latent stage
What is a low level of decontamination?
The use of disinfectants
What is an intermediate level of decontamination? (2)
Water and chlorine beach
Germicides
What is a high level of decontamination? (2)
Required for reusable devices
Chemical sterilizing solution
What is a sterilization level of decontamination? (2)
Destroys all microorganisms
Autoclave or chemical sterilizing solution
What is infectious disease?
It refers to any illness caused by a specific microorganism
