BIO 220 Chapter 13: Microbe-Human Interactions

What is the normal resident microbiota?

Microorganisms that engage in mutual or commensal associations with humans and normally reside on or in the body.

What is a pathogen?

A microbe whose relationship with its host is parasitic and results in infection and disease.

What is colonization?

The growth and establishment of microorganisms on body surfaces.

What are the three major functions of the normal microbiota?

Provide protection and stabilization of body surfaces, aid development of the immune system, and potentially cause disease if they enter sterile tissues.

What is microbial antagonism?

The ability of normal microbiota to prevent overgrowth of harmful microorganisms.

What is a transient microbe?

A microbe that occupies the body for only a short period.

What is a resident microbe?

A microbe that becomes established as part of the normal microbiota.

How does initial colonization of a newborn occur?

Through the birth canal, feeding, breathing, and natural succession.

What factors can influence the composition of normal microbiota?

Health, age, diet, hygiene, hormones, and drug therapy.

What is an endogenous infection?

An infection that occurs when normal flora enters a previously sterile site.

What is an example of an endogenous infection?

E. coli entering the bladder and causing a urinary tract infection.

What is a probiotic?

The introduction of known beneficial microbes back into the body.

What factors can disrupt the normal microbiota?

Antibiotics, dietary changes, and disease.

Which body sites commonly harbor normal resident microbes?

Skin, mucous membranes, upper respiratory tract, gastrointestinal tract, external urethra, external genitalia, vagina, external ear canal, and external eye structures.

Why are some body sites kept sterile?

To prevent infection and damage to tissues and organs.

Which internal organs and tissues are normally sterile?

Heart, circulatory system, liver, kidneys, bladder, lungs, brain, spinal cord, muscles, bones, ovaries/testes, glands, sinuses, middle and inner ear, and internal eye.

Which body fluids are normally sterile?

Blood, urine in kidneys/ureters/bladder, cerebrospinal fluid, saliva before entering the mouth, and semen before entering the urethra.

Are normal resident microbes found in the lungs?

No; lungs are normally sterile.

What are the five main stages in the development of an infection?

Portal of entry, adhesion, invasion, infection/growth, and portal of exit.

What are the major portals of entry?

Skin, gastrointestinal tract, respiratory tract, urogenital tract, and transplacental route.

What is an exogenous agent?

A microorganism that originates outside the body.

What is an endogenous agent?

A microorganism already present on or in the body as part of the normal flora.

What is adhesion?

The process by which microbes gain a stable foothold at the portal of entry.

What structures help microbes adhere to hosts?

Fimbriae, flagella, glycocalyx, cilia, suckers, hooks, barbs, capsules, and viral spikes.

How do bacteria invade tissues during infection?

By producing exoenzymes that dissolve barriers and penetrate tissues.

What are exoenzymes?

Extracellular enzymes that help microbes invade tissues.

What is coagulase?

An enzyme that promotes blood clotting.

What are kinases?

Enzymes that dissolve blood clots.

What is a toxin?

A poisonous substance produced by a microorganism that damages host tissues.

How can bacteria avoid phagocytosis?

By using a slime layer or capsule.

What are portals of exit?

Routes by which pathogens leave a host.

What are the major portals of exit?

Respiratory tract, salivary glands, skin cells, fecal matter, urogenital tract, and blood.

What factors increase susceptibility to infection?

Extreme age, immune defects, surgery, transplants, disease, chemotherapy, immunosuppressive drugs, stress, and other infections.

What is pathogenicity?

The ability or potential of a microorganism to cause disease.

What is a virulence factor?

A characteristic that helps a microbe establish itself in a host and cause disease.

What is an infectious dose (ID)?

The minimum number of microbes required for infection to occur.

How does infectious dose relate to virulence?

Microbes with smaller infectious doses generally have greater virulence.

What is the relationship between infectious dose and virulence?

Microbes with smaller infectious doses generally have greater virulence.

Will infection occur if the infectious dose is not reached?

No.

When does disease occur after infection?

When the pathogen alters normal body functions.

What are the major pathogenic groups associated with skin entry?

Staphylococcus, Streptococcus, HIV, and hepatitis viruses.

What are the major pathogenic groups associated with gastrointestinal entry?

E. coli, Salmonella, and Shigella.

What are the major pathogenic groups associated with respiratory entry?

Streptococcus pneumoniae, Klebsiella, Mycoplasma, and Cryptococcus.

What are the major pathogenic groups associated with urogenital entry?

HPV, herpes viruses, STD bacteria, and Candida.

What does STORCH stand for?

Syphilis, toxoplasmosis, other infections, rubella, cytomegalovirus, and herpes simplex.

What is the prodromal period?

A short period of vague, mild symptoms before characteristic disease symptoms appear.

What is the period of invasion?

The stage when a pathogen multiplies rapidly and characteristic signs and symptoms are most severe.

Why is the period of invasion easily recognized?

Because characteristic signs and symptoms of the disease are present.

What is the period of decline?

The stage in which pathogen numbers decrease and symptoms subside.

What is the period of convalescence?

The recovery period during which the body returns to normal.

What is a local infection?

An infection confined to one area of the body.

What is a systemic infection?

An infection that spreads throughout the body.

What is a focal infection?

A local infection that spreads to another site.

What is a mixed infection?

An infection caused by more than one microorganism.

What is an acute infection?

An infection that develops rapidly and lasts a short time.

What is a chronic infection?

An infection that develops more slowly and persists for a long period.

What is a latent infection?

An infection in which the pathogen remains dormant and may reactivate later.

What is inflammation?

A protective response to tissue injury or infection.

What are the cardinal signs of inflammation?

Redness, heat, swelling, pain, and loss of function.

Give examples of signs.

Fever, rash, swelling, redness, and elevated blood pressure.

Give examples of symptoms.

Pain, nausea, fatigue, dizziness, and headache.

What is bacteremia?

The presence of bacteria in the bloodstream.

What is a subclinical infection?

An infection that produces no noticeable signs or symptoms.

How can infections go unnoticed?

They may be subclinical and produce no obvious symptoms.

What is latency?

A dormant state in which a pathogen remains inactive but can reactivate later.

What is a chronic carrier?

A person with a latent infection who sheds the infectious agent.

What is a sequela?

Long-term or permanent damage to tissues or organs following infection.

What is epidemiology?

The study of the frequency and distribution of disease and health-related factors in populations.

What two major concerns of epidemiology involve disease transmission?

Determining where pathogens originate and how they are transmitted.

What is a reservoir?

The primary habitat of a pathogen in nature from which it originates.

What is a source?

The individual or object from which an infection is actually acquired.

What is a biological vector?

A vector in which the pathogen undergoes part of its life cycle before transmission.

What is a mechanical vector?

A vector that passively carries pathogens without supporting their growth.

What is a noncommunicable disease?

A disease that is not transmitted from one host to another.

What is direct transmission?

Transfer of a pathogen through direct contact between hosts.

What is indirect transmission?

Transfer of a pathogen through an intermediate object, vehicle, or vector.

What is a fomite?

An inanimate object that can transmit pathogens.

What is a healthcare-associated infection (HAI)?

An infection acquired during the course of receiving healthcare.

Why are HAIs important?

They increase illness, death, healthcare costs, and patient complications.

How are Standard Precautions implemented?

Through hand hygiene, use of personal protective equipment, proper handling of contaminated materials, and safe infection-control practices.