Ch 14 Study Guide Principles of Disease and Epidemiology Flashcards
Etiology
cause of disease
Pathogenesis
manner in which disease develops
Infection
invasion or colonization of the body by a pathogenic microbe
Disease
infection results in any change from a state of health
- Part or all of the body is incapable of performing its normal functions
Communicable disease
disease that is spread from one host to another
Noncommunicable disease
a disease that is not spread from one host to
another.
Ex. Tetanus (Clostridium tetani)
Symbiosis
is the relationship between normal microbiota and the
host
Commensalism, example?
one organism benefits, and the other is unaffected
ex: bacteria on the skin
Mutualism, example?
both organisms benefit
ex” bacteria in stomatch
Parasitism, example?
one organism benefits at the expense of the other
ex: tape worm
Is this typical of subacute, chronic, or acute infection?
The patient experiences a rapid onset of malaise; symptoms last 5 days.
Acute
Is this typical of subacute, chronic, or acute infection?
The patient experiences cough and breathing difficulty for months.
chronic
Is this typical of subacute, chronic, or acute infection?
The patient has no apparent symptoms and is a known carrier.
subacute
Among hospital patients who have infections, one-third do not enter the hospital with the infection but rather acquired it in the hospital. How do they acquire these infections?
Hospital patients may be in a weakened condition and therefore predisposed to infection
What is the method of transmission of these hostpital infections?
Pathogenic microorganisms are generally transmitted to patients by contact and airborne (indirect) transmission
What is the reservoir of infection for these hospital infections?
The reservoir of infection is the hospital staff, staff and other patients.
Distinguish symptoms from signs as signals of disease.
How can a local infection become a systemic infection?
An infection that is spread through the bloodstream
Why are some organisms that constitute the normal microbiota described as commensals, whereas others are described as mutualistic?
Mutualistic microorganisms are providing a chemical or environment that is essential for the host.
Commensal organisms are not essential; another microorganism might serve the function as well.
Put the following in the correct order to describe the pattern of disease: period of convalescence, prodromal period, period of decline, incubation period, period of illness.
1) Incubation period
2) Prodromal period
3) Illness period
4) Decline period
5) Convalescence period
Normal microbiota
permanently colonize the host and do not cause disease
under normal conditions
How do people acquire normal microbes (human microbiome)
during birth and the first years of life. They’re acquired from food, people and pets.
What are three ways normal microbes are beneficial to us?
- Competing for nutrients with other microbes
- Producing substances that are harmful to invaders
- Affecting the environment, pH or available oxygen to keep invaiders away
opportunistic pathogen
do not cause disease in their normal habitat in a
healthy person but may do so in a different environment
What can allow opportunistic pathogens to cause disease?
when the pathogen is displaced in an unusual location or the host has a weakened immune system
What are Koch’s 4 postulates?
- The same pathogen must be present in every case of the disease.
- The pathogen must be isolated from the diseased host and grown in pure culture.
- The pathogen from the pure culture must cause the disease when it’s inoculated into a healthy, susceptible laboratory animal.
- The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.
What are some important exceptions to Koch’s postulates?
- Some diseases caused by a variety of microbes
- Some pathogens can cause several disease conditions
- Some pathogens cause disease only in humans (would be unethical to test in humans)
- Some microbes have never been cultured
Whats Koch’s 1st Postulates?
- The same pathogen must be present in every case of the disease.
Whats Koch’s 2nd Postulate?
- The pathogen must be isolated from the diseased host and grown in pure culture.
Whats Koch’s 1st exception?
- Some diseases are caused by a variety of microbes
Whats Koch’s 2nd exception?
- Some pathogens can cause several disease conditions
Know what theory from chapter 1 Koch’s work is related to.
Germ theory of disease
How is a symptom distinct from a sign?
- Symptoms are subjective and can be perceived only by the person affected.
- Signs are objective findings that can be seen or measured
What makes a communicable disease contagious?
From one host to another
Be able to define endemic disease.
disease constantly present in a population
How does an endemic disease become an epidemic?
disease acquired by many people in a given area in a
short time
Know the difference between acute and chronic diseases.
Acute illnesses generally develop suddenly and last a short time
Chronic conditions develop slowly and may worsen over an extended period of time—months to years
Which term is used to describe a disease that is dormant because the microorganism is inactive?
Latent disease
How would you describe a subclinical infection?
no noticeable signs or symptoms, but infection is present and person can be infectious
During which periods is the number of microorganisms increasing?
incubation period
Prodromal period
In which period does death most likely occur?
Period of illness
In which period does a secondary infection most likely set in?
Period of decline
Is a person pathogen free during any of the periods?
No
What is the difference between the reservoirs?
- HUamn reservoirs invole human carriers
- Animal reservoirs involve animals as carriers
- Non-living reservoirs involve non-living things such as soil and water
What are zoonoses?
are diseases transmitted from animals to
humans
How do we acquire zoonoses?
Direct contact: Coming into contact with the saliva, blood, urine, mucous, feces, or other body fluids of an infected animal.
Examples include petting or touching animals, and bites or scratches.
What are the three forms of contact transmission?
- Direct contact: person to person
- Indirect contact: transferred by a nonliving object. (FOMITE) ex. syringes
- Droplet: microbes spread in mucus droplets. Ex: sneeze; 20k droplets.
What are the three forms of vehicle transmission?
- Air: microbes traveling more than 1 meter attached to dust particles
- Water: untreated or poorly treated sewage
- Food: food imporoperly cooked, poorly refrigerated, unsanitary conditions
You should be able to cite many examples of fomites (Indirect contact transmission)
Stethoscopes, tissues, bedding, towels etc.
- Contaminated syringes (AIDS and hepatitis B)
What is the difference between a biological and a mechanical vector?
Mechanical transmission: passive transport (pathogens on the
insect’s feet or other body parts)
Biological transmission: active process (bug bites)
What is a nosocomial infection?
healthcare-associated infections
What 3 factors contribute to nosocomial infections?
- Microorganisms in the hospital environment
- Weakened (compromised) status of the
host - Chain of transmission in a hospital
What are some examples of microbes that cause nosocomial infections
E.coli,
S. aureus,
Klebsiella species,
Enterobacter species,
Enterococcus species,
Streptococcus species,
Coagulase-negative Staphylococcus
Know the epidemiological studies talked about in lecture
John Snow: Mapped the occurance of cholera in London
Ignaz Semmelweis: Showed that handwashing decreased the incients of sepsis
Florance Nightingale: Showed that improved sanitation decreased the incidents of epidemic typhus
Explain 3 ways bacteria damage host cells
- Direct damage (viruses lysing host cells)
- Producing toxins
- Using the hosts nutrients
The prodromal period occurs prior to..
Illness
