Bio 245 Exam 4

Why are bodies great for microorganisms to be?

They are warm, stable, lots of nutrients, constant pH, and osmotic pressures

Why are our bodies not uniform environments?

Each region or organ differs: skin, GI tract, respiratory tract all provide different conditions

How do animals possess great defense mechanisms?

Only successful colonizers are those that can deal with these defenses

Why doesn't "normal" mean non-pathogenic?

We often have pathogens in low numbers in and on us

Where does colonization and infection frequently begin?

At mucous membranes

What do mucous membranes consist of?

Single or multiple layers of epithelial cells

What are epithelial cells?

tightly packed cells in direct contact with the external environment

How does bacteria associate?

Loosely or firmly

What do breaches in the mucosal barrier result in?

Infection (pathogenesis) by opportunistic pathogens

Does a human fetus normally have resident microorganisms?

No, none at all

Where does initial colonization of microorganisms come in?

During breaking of fetal membranes, and especially birth itself

What is the initial microorganisms colonization source?

Environment: mother, father, doctor, etc.

What does initial microflora depend on?

Whether the infant is breastfed or not.

What do breastfed infants normally develop?

Bifidobacterium populations

What do bottlefed infants normally develop?

A mixture of various species of coliforms: Clostridium, staphylococcus, strptococcus, lactobacillus, etc.

What do breastfed infants have in the large intestine?

Lower pH and less buffering capacity- disfavors enterobacteria and favors bifidobacteria

What does bifidobacterium seem to compete with?

Potential pathogens like clostridium difficile and some enterobacteria

Why is skin surface a largely unfavorable habitat?

Often many transient microbes

What are the exceptions of the skin microbiota?

Moister areas: scalp, face, ears, underarms, genitourinary, palms, toes

Where do most resident skin microorganisms inhabit?

In layers of the epidermis, sweat glands, and follicles

What classifies most resident skin microorganisms?

Gram positive; especially staphylococcus and propionibacterium

What parts of the skin are normally sterile?

The dermis and subcutaneous tissue

What can form communities on the skin surface?

Bacteria and fungi

What do commensal fungi form?

Hyphae or exist as individual cells

Where do viral particles live?

Freely and within bacterial cells

Where do skin mites live?

In and near hair follicles

What are the the three glands that microorganisms are primarily associated with?

1. eccrine glands

2. apocrine glands

3. sebacious glands

What are characteristics of the eccrine glands?

-widely distributed

-main glands for perspiration

-relatively devoid of microorganisms (due to salinity and low pH)

What are characteristics of the apocrine glands?

-restricted to underarms, genitals, etc.

-don't develop before puberty

-apocrine sweat has higher pH than eccrine sweat

-population numbers can be high

What are characteristics of the sebacious glands?

-associated with hair follicles

-produce sebum, chief component of skin lipids

-lipids have antibacterial activity, esp. gram positive cocci

What is the skin microbiome highly dependent on?

The microenvironment of the sampled site

Where is a great place for microbiota to live?

The human mouth (in contrast to skin)

What are the two main negatives for bacteria in the mouth?

1. salivary enzymes (lysozyme and lactoperoxidase)

2. the constant need to re-attach

How do more bacterial types arise in babies?

Once teeth emerge, there are more anaerobes and bacteria adapt to crevices and smooth surfaces

How does the biofilm of plaque form?

1. begins as thin film of glycoproteins in saliva

2. colonized (quickly) by individual cells, grows to microcolonies

3. extensive growth results in thick biofilm

What does the microbial community of dental plaque have?

Structure

What can plaque accumulate?

Calcium salts to form tartar

What is the main cause of peptic ulcers?

Infection

What is the pH of the stomach?

Low, around 2 or less

What can the stomach act as?

A microbiological barrier

What is the bacterial count of stomach contents?

Low, but walls can be heavily colonized

What is primarily in the stomach?

Lactobacillus and streptococcus

What microorganism is the cause of stomach ulcers?

Heliobacter pylori

What do the upper portions of the small intestine resemble?

The stomach; it is acidic

How many bacterium does the lower portion of the small intestine have?

10^5-10^7 per gram

How many bacterium does the large intestine have?

Enormous amounts, \>10^13 cells per gram

What is the large intestine classified as?

A chemostat

What is the size of the intestine?

Inner surface area is estimated to be the size of a tennis court

What are characteristics of the microbiota of the urogenital tract?

-bladder usually sterile

-urethra epithelium can be colonized by facultative gram neg rods

What are the types of bacteria in urogenital tract?

E. coli and proteus that can become opportunistic urinary tract pathogens

What are the bacteria in the upper respiratory tract?

Staphylococcus, streptococcus, diphtheroid bacilli, gram neg, cocci; some pathogens

What are the bacteria in the lower respiratory tract?

Few microorganisms

What is a true pathogen?

Can cause infection and disease in a healthy host

What is an opportunistic pathogen?

Only pathogenic to non-healthy individuals or when introduced into a normally sterile part of the body

What is virulence?

The degree of pathogenicity of a parasite

What are the non-specific host defenses?

normal microbiota as defense and anatomical defenses

What makes someone more susceptible to infectious disease?

-age

-stress

-diet

Why are infants more susceptible to disease?

Underdeveloped normal flora, underdeveloped immune system

Why are elderly more susceptible to disease?

Immune response declines, anatomical changes

Why does stress make one more susceptible to disease?

Fatigue, exertion, poor diet, dehydration, drastic climatic changes increase incidence and severity of infections

- hormone imbalance

Why does diet make one more susceptible to disease?

Famine and infectious disease correlated

What are the events leading to infection?

1. exposure

2. adherence

3. invasion

4. multiplication

5. toxicity or invasiveness

6. tissue or systemic damage

What are the portals of entry?

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

What are exogenous agents?

Originate from source outside the body

What are endogenous agents?

Already exist on or in the body (normal flora)

What is a serious barrier (for pathogens) to the entry of most microorganisms?

Tissue specificity

What does tissue specificity mean?

An infecting microorganism can't adhere to all cells or hosts

What are the pathogens that infect during pregnancy?

Syphillis

Toxoplasmosis

Other diseases (hepatitis B, HIV, chicken pox, and chlamydia)

Rubella

Cytomegalovirus

Herpes

What is adhesion?

Microbes gain a stable foothold at the portal of entry; dependent on binding between specific molecules on host and pathogen

How do bacteria adhere?

Through receptors

What is the infectious dose?

Minimum number of microbes required for infection to proceed

What do microbes with smaller infectious doses have?

Greater virulence

What do most cells need to cause disease?

Need to actually invade and grow in host tissues

What is colonization?

Multiplication of a microorganism after it has attached to host tissues or other surfaces