Exam IV Notecards

Module 10, 11, 12

Infection

presence and growth of a microbe in/on the host; may be asymptomatic

Disease

tissue damage or dysfunction that produces signs/symptoms

can be infectious or non-infectious

Resident Microbiota

Microbes living on/in body

includes: bac., fungi, protozoa & viruses

places thought to be sterile, now known to harbor microbes

healthy ppl often carry potential opportunists at low abundance

Microbiota Diversity

10,000 known species

1/3 common among humans

2/3 unqiue to humans

Microbiome

all genomes & genes of microbes in your body

What does Microbiota do for you?

digest certain foods

produces some vitamins (B and K)

stimulates development of certain tissues

combats opportunistic pathogens

Microbial antagonism

“good” microbes keep intrudes pathogenic microorgs. from establishing

prevents overgrowth of harmful microorgs.

Microbiomes & Health

intestinal biota profoundly influences health

Dysbiosis

imbalance of body’s microbial community

low diversity = low good bac adn high pathogenic bac.

What is dysbiosis linked to?

obesity

allergies / immune disorders

cancer

inflammatory disease

anxiety

autism

Parkinson’s disease

Where do bac come from?

Fetuses are seeded w/ normal microbiota upon birth

important for healthy fully-term pregnancies & healthy newborns

C-section births

Result in early dysbiosis

vaginal seeding

seeds C-section newborn w/bac from mother’s vagina

Continued Colonization

Breast milk: contains human milk oligosaccharides (HMOs) not digestible by rabies

used by healthy gut bac.

Critical for maintaining gut microbiome

Pathogen

microbe whose relationship with host results in infection & disease

severity of infection depends on pathogenicity

Pathogenicity

Organism’s potential to cause infection or disease

Qualitivative measureT

True pathogens

cause disease in healthy

Opportunistic pathogens

cause disease in: host w/ compromised immune defenses

non-normal body part

Virulence

relative severity of the disease

Quantitative measure

Virulence factors

structures, products, or capabilities allowing pathogen to cause infection

infectious dose (ID)

number of microbes for infections; fewer bac. → NO infection

ID varies between microbes

low ID → high virulence

Portal of entry

route taken by microbe to start infection

Exogenous infection

originate outside the body

environment, another person, animal

Endogenous infection

Caused by resident biota

microorg in a non-normal site

Entry Portals

broken skin

GI tract

respiratory tract

urogenital system (inc. STD)

pregnancy & birth

Adhesion

Microbes gain foothold in host tissues

binding of specific host & pathogen molecules

then invades body compartments

Phagocytes

white blood cells (wbc): engulf & destroy pathogens (phagocytosis)A

Antiphagocytic factors

Virulence factors used by pathogens. to avoid wbc.

Antiphagocytic factors examples

leukocidins

slime layer/capsule

SOME pathogens can survive in wbc.

Leukocidins

kill phagocytes

Slime layer / capsule

hinders wbc.

What causes disease

virulence factors

directly

indirectly

Directly

toxins or enzymes

Exoenzymes

secreted by pathogenic organisms

Extracellular Enzymes

Exoenzymes

break down & damage tissues

dissolve defense barriers: spread to deeper tissues

Indirect Virulence

host’s excessive or inappropriate immune response

causes many cases of microbial disease

What is the result of interplay?

Pathogenicity & disease between microbe & host

How to vacate the host?

normal body processes

vectors

Normal body processes

Respiration & saliva

skin scales

feces

urigenital tract

bloodVe

Vectors

Blood feeding animals:

Ticks

Fleas

Mosquitoes