Microbiology - Infection, Infectious Diseases, and Epidemiology (Ch. 14)

Epidemiology  is the study of the occurrence, distribution, and spread of disease in humans.

(14, 402)

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.

(14, 402)

• 1) Mutualism
• Both members benefit from their relationship.
• 2) Commensalism
• One member benefits from the relationship without significantly affecting the other.
• 3) Parasitism
• The parasite derives benefit from its host while harming it. 

(14, 402-403)

A pathogen is any parasite that causes disease.

(14, 403)

Axenic refers to sites that are free of an microbe.

(14, 403)

• 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.

(14, 403)

• 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.

(14, 404)

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. 

(14, 404)

Any source in which an infectious agent normally lives and multiplies.

(14, 406)

Zoonoses are diseases that spread naturally from their usual animal hosts to humans.

(14, 406)

Occurring in or affect wild animals.

(14, 406)

• 1) Soil
• 2) Water
• 3) Food

(14, 407)

Infection is a successful invasion of the body by a pathogenic microorganism.

(14, 407)

• 1) Skin
• 2) Mucous Membranes
• 3) Placenta

(14, 407)

The conjunctiva is a thin membrane that covers the inner surface of the eyelid and the white part of the eyeball (the sclera).

(14, 408)

The process by which microorganisms attach themselves to cells.

(14, 409)

They are specialized structures or attachment proteins used to accomplish adhesion.

(14, 409)

They are surface lipoprotein and glycoprotein molecules that are used by viruses and many bacteria to adhere to cells.

(14, 409)

Ligands are also referred to adhesins on bacteria, or attachment proteins on viruses.

(14, 409)

Not virulent.

(14, 409)

A disease is any adverse internal condition severe enough to interfere with normal body functioning.

(14, 410)

Any change from a state of health.

(14, 410)

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. 

(14, 410)

A syndrome is a group of symptoms and signs that collectively characterizes a particular disease or abnormal condition.

(14, 410)

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.

(14, 410)

Etiology is the study of the cause of a disease.

(14, 410)

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.

(14, 411)

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.

(14, 413)

Factors that affect the relative ability of a pathogen to infect and cause disease.

(14, 413)

• 1) Adhesion factors
• 2) Biofilm formation
• 3) Extracellular enzymes
• 4) Toxins
• 5) Antiphagocytic factors

(14, 413-416)

Blood poisoning resulting from the presence of toxins in the blood.

(14, 414)

A poisonous substance produced by an organism that can cause disease when introduced into the body.

(14, 414)

• 1) Cytotoxins
• Kill 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.

(14, 414)

Antibodies that that bind to specific toxins and neutralize them.

(14, 414)

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.

(14, 414)

Gram-negative bacteria produce endotoxins. The endotoxin is called Lipid A.

(14, 415-416)

• 1) Capsules
• 2) Antiphagocytic chemicals

(14, 416)

A definite series of events following contamination and infection.

(14, 416)

• 1) Incubation Period
• 2) Prodromal Period
• 3) Illness
• 4) Decline
• 5) Convalescence

(14, 416-417)

The exit site of a pathogen through which it leaves the body.

(14, 417)

• 1) Contact transmission
• 2) Vehicle transmission
• 3) Vector transmission

(14, 418-420)

• 1) Direct contact transmission
• 2) Indirect contact transmission
• 3) Droplet transmission

(14, 418)

If pathogens travel more than 1 meter in respiratory droplets, it is considered to be airborne transmission. Otherwise it is droplet transmission.

(14, 418)

Inanimate objects that are inadvertently used to transfer pathogens to new hosts.

(14, 418)

• 1) Airborne transmission
• 2) Waterborne transmission
• 3) Foodborne transmission

(14, 418-419)

• 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.).

(14, 420)

• 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) Latent
• Disease where pathogen remains inactive for a long time before becoming active (i.e. herpes).

(14, 420)

• 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.

(14, 421)

• 1) Incidence
• The number of new cases of a disease in a given area or population during a given period of time.
• 2) Prevalence
• The total number of cases, both new and already existing, in a given area or population during a given period of time.

(14, 421)

• 1) Endemic
• A disease is occurring at a relatively stable incidence within a given population or area.
• 2) Sporadic
• A disease only has a few scattered cases occurring within a given population or area.
• 3) Epidemic
• A disease occurs at a greater than normal frequency than is usual for an area or population.
• 4) Pandemic
• An epidemic that occurs simultaneously on more than one continent.

(14, 422)

• 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)

Infections and diseases acquired by patients or health care worker while they are in health care facilities.

(14, 426)

10%

(14, 426)

• 1) Exogenous nosocomial infections
• Caused by pathogens acquired from the health care environment.
• 2) Endogenous nosocomial infections
• Arise from normal microbiota within a patient that become pathogenic because of factors within the health care setting.

(14, 428)

A toxoid is an inactivated toxin used in a vaccine.

(14, 414)