Principles of Disease and Epidemiology Flashcards
Nosocomial Disease
can also be called a HAI a disease that is contracted in a healthcare facility.
Pathology
Study of disease
Pathogen
Pathogenic agents have special properties that allow them to invade the human body or produce toxins
Etiology
the study of the cause of a disease
Infection
invasion and growth of pathogens in the body
Disease
Abnormal state in which the body is not functioning normally.
ex. infectious agent overcomes body’s defenses
Pathogenesis
The development of disease
What is the protective role of normal microbiota?
- Prevent pathogens from attaching
- Consume available nutrients
- Produce toxic compounds that inhibit other microbes
Microbial Antagonism
- When established cultures of microorganisms prevent the intrusion of foreign strains. When introduced to an already-colonized environment, an invasive strain of bacteria tends not to thrive and may go completely extinct.
- Microbial antagonism is due to competition between microbes.
Resident flora
- Normal microbiota (acquired at passage through birth canal)
- Establish permanent colonies on/inside body without producing disease. Protect the host by
1. Occupying niches that pathogens might occupy (Competitive exclusion)
2. Producing acids
3. Producing bacteriocins
4. Stimulation of immune system
Transient Microbiota (Flora
Certain microbes are present for various periods (days, weeks, or months) – then disappears.
Probiotics
Live microbes applied to or ingested into the body, intended to exert a beneficial effect
Describe the dynamic nature of resident flora
changes due to age, type of food consumed, Hormonal state, antibiotics
Various Co-existance (symbiotic) Relationships Between Bacteria and Host
- Commensalism
- Mutualism
- Parasitism
Commensalism
One organism benefits and the other is unaffected
Mutualism
Both organisms benefit
Parasitism
one organism benefits at the expense of another
Symbiosis
relationship between 2 organisms in which at least one organism is dependent on the other
Opportunistic pathogens
cause disease under special conditions (mutualistic relationship becomes parasitic)
Healthy carriers of pathogenic organisms
An asymptomatic carrier (healthy carrier or just carrier) is a person or other organism that has contracted an infectious disease, but who displays no symptoms. Although unaffected by the disease themselves, carriers can transmit it to others.
How do microbes cooperate with each other?
One microorganism may make it possible for another to cause disease or produce more severe symptoms
Koch’s Postulates
provide proof of etiology of infectious disease
What are Koch’s 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 is inoculated into a healthy, susceptible lab animal
- The pathogen must be isolated from the inoculated animal and must be shown to be the original microbe
Key concepts of Koch’s postulates
- according to koch’s postulates, a specific infectious disease is caused by a specific microbe
- Koch’s postulates help determine the etiology of disease, the first step in treatment and prevention
- Microbiologists use these steps to identify the causes of emerging diseases
What are the exceptions to Koch’s postulates?
These exceptions made it necessary to modify Koch’s postulates:
- to establish disease etiology for viruses and certain bacteria, which cannot be grown on artificial media
- Some diseases, e.g.: pneumonia, meningitis, and nephritis, may be caused by a variety of microbes.
- Some pathogens, such as S. progenies, cause several different diseases.
- Certain pathogens, such as HIV, cause disease in humans only.
How are infectious diseases classified?
- Communicable
- Non-communicable
- Contagious
Symptom
A change in body function that is felt by a patient as a result of disease. Symptoms are subjective
Sign
A change in a body that can be measured or observed as a result of disease. Signs are objective
Syndrome
A specific group of signs and symptoms that accompany a disease
Communicable Disease
A disease that is spread from one host to another (genital herpes, TB)
Non-communicable Disease
A disease that is not transmitted from one host to another (tetanus, ulcers)
Contagious Disease
A disease that is easily spread from one host to another (common cold, chickenpox)
Incidence
Fraction of a population that contracts a disease during a specific time (new cases)
Prevalence
Fraction of a population having a specific disease at a given time
Sporadic disease
Disease that occurs occasionally in a population
Endemic disease
Disease constantly present in a population
Epidemic disease
Disease acquired by many hosts in a given area in a short time