Microbiology - Infection, Infectious Diseases, and Epidemiology (Ch. 14)
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What is epidemiology?
Epidemiology is the study of the occurrence, distribution, and spread of disease in humans.
What is symbiosis?
Symbiosis is a continuum of close associations between two or more organisms that ranges from mutually beneficial to associations in which one member damages the other member.
List and explain the three different main types of symbiotic relationships.
- 1) MutualismBoth members benefit from their relationship.
- 2) CommensalismOne member benefits from the relationship without significantly affecting the other.
- 3) ParasitismThe parasite derives benefit from its host while harming it.
What is a pathogen?
A pathogen is any parasite that causes disease.
What does axenic refer to?
Axenic refers to sites that are free of an microbe.
What is normal microbiota?
What are two other names for it?
- Normal microbiota are the microbes that colonize surfaces of the body without normally causing disease.
- They are also referred to as normal flora or indigenous microbiota.
List and explain the two main types of normal microbiota.
- 1) Resident Microbiota
- These microbiota remain part of the normal microbiota throughout life. They establish themselves usually within the first months of your life.
- 2) Transient Microbiota
- Only remain on the body for a few hours, days, or months. They cannot persist because of competition for nutrients, our body's defensive cells, or chemical and physical changes that dislodge them from the body.
List three conditions that can create opportunities for normal microbiota to become opportunistic pathogens.
1) Introduction of a member of the normal microbiota into an unusual site in the body.
2) Immune suppression.
3) Changes in the normal microbiota.
What are reservoirs of infection?
Any source in which an infectious agent normally lives and multiplies.
What are zoonoses?
Zoonoses are diseases that spread naturally from their usual animal hosts to humans.
What does the term sylvatic refer to?
Occurring in or affect wild animals.
Give three examples of nonliving reservoirs of infection.
What is infection?
Infection is a successful invasion of the body by a pathogenic microorganism.
What are the three major portals of entry for a pathogen on the body?
- 1) Skin
- 2) Mucous Membranes
- 3) Placenta
What is the conjunctiva?
The conjunctiva is a thin membrane that covers the inner surface of the eyelid and the white part of the eyeball (the sclera).
What is adhesion?
The process by which microorganisms attach themselves to cells.
What are adhesion factors?
They are specialized structures or attachment proteins used to accomplish adhesion.
What are ligands?
They are surface lipoprotein and glycoprotein molecules that are used by viruses and many bacteria to adhere to cells.
What are ligands also referred to as on bacteria?
Ligands are also referred to adhesins on bacteria, or attachment proteins on viruses.
What does avirulent refer to?
What is disease?
A disease is any adverse internal condition severe enough to interfere with normal body functioning.
What does morbidity refer to?
Any change from a state of health.
Compare symptoms and signs.
Symptoms are subjective characteristics of a disease that can be felt only by the patient. Signs are objective manifestations of a disease that can be observed or measures by other.
What is a syndrome?
A syndrome is a group of symptoms and signs that collectively characterizes a particular disease or abnormal condition.
What does asymptomatic refer to?
What is another name for it?
Asymptomatic is characteristic of a disease that may go unnoticed because of the absence of symptoms, even though clinical tests may reveal signs of disease.
It is also referred to as subclinical.
What is etiology?
Etiology is the study of the cause of a disease.
List all four of Koch's Postulates.
1) The suspected agent must be present in every case of the disease.
2) That agent must be isolated and grown in pure culture.
3) The cultured agent must cause the disease when it is inoculated into a healthy, susceptible experimental host.
4) The same agent must be reisolated from the diseased experimental host.
Compare pathogenicity and virulence.
Pathogenicity is the ability of a microbe to cause disease. Virulence is degree of pathogenicity (the relative ability of a pathogen to infect a host and cause disease).
*NOTE: Neither refers to the severity of a disease.
What are virulence factors?
Factors that affect the relative ability of a pathogen to infect and cause disease.
Give 5 examples of virulence factors.
- 1) Adhesion factors
- 2) Biofilm formation
- 3) Extracellular enzymes
- 4) Toxins
- 5) Antiphagocytic factors
What is toxemia?
Blood poisoning resulting from the presence of toxins in the blood.
What is a toxin?
A poisonous substance produced by an organism that can cause disease when introduced into the body.
List and explain the three principal types of exotoxins.
- 1) CytotoxinsKill host cells in general or affect their function.
- 2) Neurotoxins
- Specifically interfere with nerve cell function.
- 3) Enterotoxins
- Affect the cells lining the gastrointestinal tract.
What are antitoxins?
Antibodies that that bind to specific toxins and neutralize them.
What are toxoids?
They are toxins that have been treated with heat or chemicals to make them non-toxic but still capable of stimulating the production of antibodies.
Although both classes can produce exotoxins, what class of bacteria also produces endotoxins?
What is the endotoxin called?
Gram-negative bacteria produce endotoxins. The endotoxin is called Lipid A.
What are two examples of antiphagocytic factors?
- 1) Capsules
- 2) Antiphagocytic chemicals
What is disease process?
A definite series of events following contamination and infection.
In sequential order, what are the five stages that occur following an infection?
- 1) Incubation Period
- 2) Prodromal Period
- 3) Illness
- 4) Decline
- 5) Convalescence
What are portals of exit?
The exit site of a pathogen through which it leaves the body.
What are the three categories of transmission for a pathogen?
- 1) Contact transmission
- 2) Vehicle transmission
- 3) Vector transmission
What are the three types of contact transmission?
- 1) Direct contact transmission
- 2) Indirect contact transmission
- 3) Droplet transmission
What is the difference between droplet transmission and airborne transmission?
If pathogens travel more than 1 meter in respiratory droplets, it is considered to be airborne transmission. Otherwise it is droplet transmission.
What are fomites?
Inanimate objects that are inadvertently used to transfer pathogens to new hosts.
What are the three types of vehicle transmission?
- 1) Airborne transmission
- 2) Waterborne transmission
- 3) Foodborne transmission
What are the two types of vector transmission?
Briefly explain each one.
- 1) Biological vectors
- These are living organisms and they not only transmit pathogens but also serve as hosts for the multiplication of the pathogen during some part of the pathogen's life cycle (i.e. mosquitos, ticks, fleas, etc.).
- 2) Mechanical vectors
- Vectors that passively carry pathogens to new hosts on their body parts, but are not required to as hosts to the pathogens that the transmit (i.e. houseflies, cockroaches, etc.).
Compare acute, chronic, subacute diseases, and latent diseases.
- 1) Acute
- Disease develops rapidly but lasts a short time (i.e. cold).
- 2) Chronic
- Develop slowly (usually with less severe symptoms) and are continual or recurrent (i.e. Hepatitis C, leprosy).
- 3) Subacute
- Fall somewhere in between acute and chronic (i.e. a disease of heart valves).
- 4) LatentDisease where pathogen remains inactive for a long time before becoming active (i.e. herpes).
Compare communicable, noncommunicable,
- 1) Communicable
- Disease comes from another infected host, either directly or indirectly.
- 2) Noncommunicable
- Disease arises outside of host or from normal microbiota. They are not spread from one host to another. (i.e. tooth decay, acne, tetanus)
- 3) Contagious
- Communicable disease that is easily transmitted.
Epidemiologists keep track of the occurrence of diseases using two measures: incidence and prevalence. Compare the two.
- 1) IncidenceThe number of new cases of a disease in a given area or population during a given period of time.
- 2) PrevalenceThe total number of cases, both new and already existing, in a given area or population during a given period of time.
Compare endemic, sporadic, epidemic, and pandemic.
- 1) EndemicA disease is occurring at a relatively stable incidence within a given population or area.
- 2) SporadicA disease only has a few scattered cases occurring within a given population or area.
- 3) EpidemicA disease occurs at a greater than normal frequency than is usual for an area or population.
- 4) PandemicAn epidemic that occurs simultaneously on more than one continent.
What are the three different approaches to epidemiology?
Briefly explain them.
- 1) Descriptive epidemiology
- Involves careful tabulation of data concerning the disease.
- 2) Analytical epidemiology
- Investigates a disease in detail (including looking at descriptive epidemiology) to determine probable cause, transmission, and prevention of disease.
- 3) Experimental epidemiology
- Involves testing a hypothesis concerning the cause of a disease.
- (14, 424-426)
What are nosocomial infections/diseases?
Infections and diseases acquired by patients or health care worker while they are in health care facilities.
The CDC estimates that what % of American patients acquire a nosocomial infection each year?
Compare exogenous and endogenous nosocomial infections.
- 1) Exogenous nosocomial infectionsCaused by pathogens acquired from the health care environment.
- 2) Endogenous nosocomial infectionsArise from normal microbiota within a patient that become pathogenic because of factors within the health care setting.
What is a toxoid?
A toxoid is an inactivated toxin used in a vaccine.
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