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

Lecture 12 - Human-Microbe Interactions Flashcards

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1
Q

How many microbes does each human body host?

A

40 trillion

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2
Q

What does the following terminology mean

-Microbiota, Microbiome, ‘‘Normal Microflora’’

A

Microbiota = microflora

-all microbial species

Microbiome

-all microbial species+their function

'’Normal’’ Microflora

-microbes in a healthy human body

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3
Q

Where do normal microflora live and not live?

A

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
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4
Q

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

A

Diifferent body areas make for different microenvironments

Habitat conditions

  • Oxygen levels
  • Acidity, pH
  • Available Nutrients
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5
Q

What kinds of effects can normal microflora have?

A

Benign (most)

  • no positive/negative effects
  • occupy human microhabitats

Beneficial (some)

  • positive effects
  • metabolism and defense

Pathogenic (few)

  • negative effects
  • cause infectious disease
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6
Q

How are normal microflora established?

A

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
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7
Q

What is a pathogen?

A

live on/in hosts and cause disease

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8
Q

what is pathogenicity?

A

ability of pathogen to cause disease

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9
Q

what are opportunistic pathogens?

A

cause disease in the absence of normal host resistance

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10
Q

what are the surface areas of the normal microflora environments?

A

Skin

-medium surface area

Oral Cavity

-small surface area

Gastrointestinal tract

-very large surface area

Mucosal tissue

-large surface area

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11
Q

What kinds of microenvironments does the skin have?

A

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
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12
Q

What factors affect the skin microflora?

A

Host Factors

  • Age: higher variability and more pathogens in young vs adult
  • Personal hygeine: more microbes

Environmental Factors

-Weather: affect skin temp and moisture

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13
Q

What disrupts the normal skin microflora?

A

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

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14
Q

What are the characteristics of the oral cavity?

A

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

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15
Q

How are dental plaques and tooth decay related?

A

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

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16
Q

How do you prevent dental caries?

A

restrict sucrose

-sucrose allows bacteria to produce substance to adhere to teeth

brush teeth

enhance enamel w/ flouride

17
Q

What are the characteristics of the gastrointestinal tract?

A

Heterogeneous Habitat

  • stomach
  • small/large intestines

Antimicrobial conditions

-low pH

Lots of Nutrients Sources

-variety of food intake

18
Q

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

A

Inversely correlated

  • low pH = High oxygen level
  • high pH = low oxygen level
19
Q

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

A

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
Q

What are the functions of gastrointestinal microbes?

A

Vitamin Synthesis

Steroid metabolism

Produce gas

21
Q

What is microflora turnover?

A

10 trillion bacteria removed each day

-fecal matter is 1/3

Remaining populations double 1-2x per day

22
Q

How is a large intestine similar to a chemostat?

A

Open system

Log phase growth

23
Q

What does disrupting the normal intestinal microflora result in?

A

Diarrhea

-side effect of oral antibiotics

Alteration of digestive function

-impaired vitamin synthesis

Pathogen colonization

-no competition from normal microbes

24
Q

How do we restore normal intestinal microflora?

A

Probiotics

Fecal Microbiota Transplant

25
Q

What are the characteristics of mucosal tissues?

A

Heterogeneous habitat

  • upper vs lower respiratory
  • urogenital tract

Antimicrobial conditions

-entrapment, removal, low pH in vagina

Low Diversity of Microbes

26
Q

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

A

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

27
Q

Is the urogenital tract exposed to environmental microbes?

A

Urethra

-facultative anaerobes

Vagina

-lactic acid bacteria that maintain low pH environment

28
Q

What is virulence and what is pathogenesis?

A

Virulence

-measure of pathogenicity

Pathogenesis

-process by which microbes cause disease

29
Q

How do we measure virulence?

A

LD50

  • amount of pathogen that kills 50% of hosts
  • low LD50 = high virulence
  • high LD50 = low virulence
30
Q

What is attenuation?

A

Decrease or loss of virulence

-used in vaccines

In nature attenuation is selected for

-pathogenic to mutualism

31
Q

What are the steps of pathogenesis?

A

Adherence

Invasion

Infection

32
Q

What is the step of pathogenesis, adherence?

A
  • attachment to host cells
  • very specific
  • uses slime layers and pili
33
Q

What is the step of pathogenesis, invasion?

A

Invasion

entering host tissues and causing damage

-most invasions occur thorugh wounds

Infection

Growth/production of toxins and virulence factors

34
Q

What are virulence factors and toxins?

A

Virulence Factors

-promote colonization and growth

Toxins

-inhibit cell function or kills cells

35
Q

What are the types of toxins?

A

EXOTOXINS

-produced inside released from pathogen cells

ENDOTOXINS

  • Not released from pathogenic cells
  • present in LPS of outer membrane
  • less toxic than exotoxins
36
Q

What are the types of exotoxins?

A

Cytolytic

-damage cytoplasmic membrane of host cell causing lysis

AB

  • INHIBIT INTERNAL CELL FUNCTIONS
  • most
37
Q

What are the host barriers to infection?

A

Physical

-skin

Chemical

  • antimicrobials
  • low pH

Biological

-competition w/ other microflora

38
Q

What are the risk factors for host infection to pathogens?

A

Age, diet, stress

BIO 425: Microbiology (22 decks)

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