Lecture 12 - Human-Microbe Interactions Flashcards Preview

BIO 425: Microbiology > Lecture 12 - Human-Microbe Interactions > Flashcards

Flashcards in Lecture 12 - Human-Microbe Interactions Deck (38)
Loading flashcards...
1

How many microbes does each human body host?

40 trillion

2

What does the following terminology mean

-Microbiota, Microbiome, ''Normal Microflora''

Microbiota = microflora

-all microbial species

Microbiome

-all microbial species+their function

''Normal'' Microflora

-microbes in a healthy human body

3

Where do normal microflora live and not live?

LIVE

-Skin, respiratory tract, digestive tract, urogenital tract

-all exposed to environment

DON'T LIVE

-Internal organs

-Blood, lymph, nervous system

-Not exposed to environment

4

Why do normal microflora live in areas exposed to the environment?  What kinds of habitat conditions factor into their choice of environment?

Diifferent body areas make for different microenvironments

 

Habitat conditions

-Oxygen levels

-Acidity, pH

-Available Nutrients

5

What kinds of effects can normal microflora have?

Benign (most)

-no positive/negative effects

-occupy human microhabitats

Beneficial (some)

-positive effects

-metabolism and defense

Pathogenic (few)

-negative effects

-cause infectious disease

6

How are normal microflora established?

Humans are born without exposure to microbes

-uterus is sterile environment so born without microflora

 

Colonization of microbes

-horizontally transmitted from environment

-enters body and grows

7

What is a pathogen?

live on/in hosts and cause disease

8

what is pathogenicity?

ability of pathogen to cause disease

9

what are opportunistic pathogens?

cause disease in the absence of normal host resistance

10

what are the surface areas of the normal microflora environments?

Skin

-medium surface area

Oral Cavity

-small surface area

Gastrointestinal tract

-very large surface area

Mucosal tissue

-large surface area

11

What kinds of microenvironments does the skin have?

Multiple with different chemical and physical conditions resulting in different populations of bacteria

Sebaceous

-upper chest

-oily areas

Moist Skin

-armpits

-high moisture

Dry Skin

-forearms

-low moisture

12

What factors affect the skin microflora?

Host Factors

-Age: higher variability and more pathogens in young vs adult

-Personal hygeine: more microbes

Environmental Factors

-Weather: affect skin temp and moisture

 

13

What disrupts the normal skin microflora?

Acne

-pore blockage by bacteria

Body Odor

-gases released by microbial metabolism

Disease

-resident microbes prevent pathogen colonization

Mosquitoes

-type of skin microbiome correlates with mosquitoes

14

What are the characteristics of the oral cavity?

Heterogeneous Habitat

Antimicrobial chemicals present in oral cavity

-saliva has lysozyme

Nutrient sources

-food particles and cell debris near teeth/gums

High diversity of microbes

Primarily anaerobic metabolism

-facultive and obligate anaerobes

Colonize tooth surfaces

-form bacterial layers, biofilms, called dental plaques

15

How are dental plaques and tooth decay related?

Dental plaques that form on teeth undergo anaerobic metabolism and produce lactic acid decaying the teeth

 

High sugar intake results in tooth decay because fermentation of sugars produce the lactic acid

16

How do you prevent dental caries?

restrict sucrose

-sucrose allows bacteria to produce substance to adhere to teeth

 

brush teeth

 

enhance enamel w/ flouride

17

What are the characteristics of the gastrointestinal tract?

Heterogeneous Habitat

-stomach

-small/large intestines

Antimicrobial conditions

-low pH

Lots of Nutrients Sources

-variety of food intake

18

What is the relationship between pH and oxygen level in the gastrointestinal tract?

Inversely correlated

-low pH = High oxygen level

-high pH  = low oxygen level

19

What are the characteristics of the stomach, small intestine and large instestine?

Stomach

-highly acidic, pH=2

-only acidophiles survive

Small intestine

-fairly acidic, pH=4.5

-similar to stomach but more microbes as pH increases

Large intestine

-neutral pH = 7

-strictly anoxic, no oxygen

-largest number of microbes

-fermentation vessel

20

What are the functions of gastrointestinal microbes?

Vitamin Synthesis

Steroid metabolism

Produce gas

21

What is microflora turnover?

10 trillion bacteria removed each day

-fecal matter is 1/3

Remaining populations double 1-2x per day

22

How is a large intestine similar to a chemostat?

Open system

Log phase growth

23

What does disrupting the normal intestinal microflora result in?

Diarrhea

-side effect of oral antibiotics

Alteration of digestive function

-impaired vitamin synthesis

Pathogen colonization

-no competition from normal microbes

24

How do we restore normal intestinal microflora?

Probiotics

Fecal Microbiota Transplant

25

What are the characteristics of mucosal tissues?

Heterogeneous habitat

-upper vs lower respiratory

-urogenital tract

 

Antimicrobial conditions

-entrapment, removal, low pH in vagina

 

Low Diversity of Microbes

26

Is the upper or lower respiratory tracts exposed to airborne microbes?

Upper yes but lower no b/c removal by ciliated epithelia cells

27

Is the urogenital tract exposed to environmental microbes?

Urethra

-facultative anaerobes

Vagina

-lactic acid bacteria that maintain low pH environment

28

What is virulence and what is pathogenesis?

Virulence

-measure of pathogenicity

Pathogenesis

-process by which microbes cause disease

29

How do we measure virulence?

LD50

-amount of pathogen that kills 50% of hosts

-low LD50 = high virulence

-high LD50 = low virulence

30

What is attenuation?

Decrease or loss of virulence

-used in vaccines

 

In nature attenuation is selected for

-pathogenic to mutualism