Bio251a: Chapter 13 Microbe-Human Interactions Infection, Disease, and Epidemiolog [part one]

What is Normal Resident microbiota?

microbes that engage in mutual or commensal associations with humans

What is an example of Normal Resident microbiota?

commensals

What is Infection?

microbe that has penetrated the host defenses, invaded sterile tissue, and multiplied

What is Disease?

damage to host, any deviation from health

What is Pathogen?

disease-causing microbe

In pregnancy, how sterile is the uterus?

Uterus and contents are normally sterile and remain so until just before birth

What occurs during birth?

Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora

What is flora?

the community of microorganisms (bacteria, fungi, viruses) that live in and on a host body

What are factors that weaken hosts defenses and increase susceptibility to infection?

- old age/extreme youth,

- genetic/acquired defects in immunity,

- surgery and organ transplant,

- organic disease (cancer, liver malfunction, diabetes)

- chemotherapy/immunosuppressive drugs

- physical/mental stress

- other infection

What are the Major Factors in the Development of an Infection? (7)

1.) portal of entry

2.) adhesion

3.) invasion

4.) multiplication

5.) infection of target

6.) disease

7.) portal of exit

What is portals of entry?

characteristic route a microbe follows to enter the tissues of the body

What are the two agents?

Exogenous agents and Endogenous agents

What are Exogenous agents?

originate from source

outside the body

What are Endogenous agents

already exist on or in the body (normal microbiota)

What are the different portals of entry?

Skin, Gastrointestinal tract, Respiratory tract, Urogenital tract, Transplacental

What are examples of skin portals of entry?

nicks, abrasions,

punctures, incisions

What are examples of Gastrointestinal tract portals of entry?

food, drink, and otheringested materials

What are examples of Respiratory tract portals of entry?

oral and nasal cavities

What are examples of Urogenital tract portals of entry?

sexual, displaced organisms

What are examples of transplacental portals of entry?

Mother's Bloodstream to Fetus

What acronym can be used to describe Pathogens That Infect during Pregnancy?

STORCH; Syphilis, Toxoplasmosis, Other diseases (hepatitis B, AIDS and chlamydia), Rubella,

Cytomegalovirus and Herpes simplex virus

What is Infectious Dose?

Minimum number of microbes required for infection to proceed

Is a microbe more powerful if it has a smaller IDs or a greater IDs?

small IDs have greater virulence

What is a microbe has a lack of ID?

will not result in infection

What is adhesion?

allows microbes gain a stable foothold at the portal of entry; dependent on binding between specific molecules on

host and pathogen

What components of bacteria assist in adhesion?

- Fimbrae

- Flagella

- Glycocalyx

- Cilia

- Suckers

- Hooks

- Barbs

- Viral spikes

What are Virulence factors?

traits used to invade and

establish themselves in the host; determine the

degree of tissue damage that occurs and severity of disease

What are components of virulence factors?

▪ Blocking phagocytosis

▪ Invasion factors

▪ Exoenzymes

▪ Toxins

What are components of Blocking Phagocytosis?

Antiphagocytic factors, Leukocidins, Slime layer or capsule

What is the function of blocking phagocytosis?

Increasing ability to survive intracellular phagocytosis

What is the function of Antiphagocytic factors?

used to avoid phagocytosis

What is the function of Leukocidins? How is it produced?

toxic to white blood cells; produced by species of Staphylococcus and

Streptococcus

What is the function of Slime layer or capsule?

makes phagocytosis difficult

What are invasion factors? Give an example.

pathogens produce a secretion system to

insert specialized virulence proteins directly into the host cells,

- ex. Salmonella

What are exoenzymes?

extracellular

enzymes; secreted

by a cell and functions outside that cell

What is significant about the exoenzymes produced by Staphylococcus and Streptococcus spp.?

can produce exoenzymes that dissolve extracellular barriers and penetrate through or between cells

What are examples of exoenzymes?

Mucinase, keratinase, collagenase,

hyaluronidase, coagulase,

strepto/sphaylokinase

What are bacterial toxins?

Potent Source of Cellular Damage

What is toxigenicity?

capacity to produce toxins at the site

of multiplication

What are the two types of bacterial toxins?

Endotoxin and Exotoxin

What is an endotoxin?

toxin that is not secreted but is released after the cell is damaged

What is an example of an endotoxin?

Components of lipopolysaccharide (LPS), part of the outer membrane of gram-negative cell walls

What is a exotoxin?

toxin molecule secreted by a living bacterial cell into the infected tissue; Strong specificity for a target cell

What are examples of exotoxins?

Hemolysins, A-B toxins (A-active, B-binding)

What occurs as a result of exotoxins?

Target organs are damaged; heart, muscles, blood cells, intestinal tract show dysfunctions.

What occurs as a result of endotoxins?

General physiological effects- fever , malaise, aches, shock

How do A-B Exotoxins work?

1.) The A (active) component is attached to the B (binding) component

2.) The A component inhibits a cellular protein to cause the damage

Capsules and slime layers can help pathogensevade the immune system by___.

Prevent phagocytic activity