Host - Pathogen Interaction

Question 1

What are the four types of bacteria based on their host-pathogen interaction?

Answer 1

1. Saprophytic - dead organic matter
2. Commensal/Mutualistic - Live on/in host without harm/benefit (unless mutualistic)
3. Obligate pathogens - always cause disease in host regardless of immune system
4. Usually harmless, but can cause disease in weakened body or other parts of body

Question 2

What is the general nature of most bacteria and humans?

Answer 2

Most harmless, many beneficial

Question 3

Define microbiome

Answer 3

functional collection of different microbes in a particular system

Question 4

What term describes all the microbes in a microhabitat?

Answer 4

Microbiota

Question 5

How many bacterial cells are carried in a human?

Answer 5

About the same - 10^13-10^14

Question 6

What is the genetic significance of the microbiota of humans?

Answer 6

The amount of bacteria carries about 100 times more nonredundant bacterial genes

Question 8

Is the skin easy or difficult to colonize? Why?

Answer 8

Difficult due to it being dry, salty, acidic, and having oils

Question 9

How many bacteria are found on human skin?

Answer 9

1 million/square centimeter, and about 10^10 for an adult

Question 10

What influences the composition of skin bacteria?

Answer 10

Environmental factors - pets, weather

Host factors - age, hygeine

Question 11

What skin is Proteobacteria found on?

Answer 11

Dry Skin

Question 11

What are the three sub environments of skin?

Answer 11

1. Dry skin
2. Moist Skin
3. Sebaceous skin

Question 11

What type of skin are Corynebacterium and Staphylococcus mound on?

Answer 11

Moist skin

Question 11

What type of bacteria is mostly found on skin and why?

Answer 11

Gram positive bacteria, as they are more resistant to saltiness

Question 11

What does complex heterogeneous microbial habitat mean and how does it relate to the oral cavities/airways?

Answer 11

There are many microhabitats that exist, eg. many different oral cavities and sections of tract

Question 12

Where does bacteria enter the airway?

Answer 12

Upper respiratory tract

Question 13

What happens to most bacteria that enter the oral cavities and airways?

Answer 13

They are trapped in mucus and expelled

Question 14

What type of microbiota is found in the lungs?

Answer 14

Normal limited

Question 15

What are the most prevalent bacteria found in the lungs?

Answer 15

Streptococcus, Prevotella, and veillonella

Question 16

What is the mucociliary escalator?

Answer 16

The ciliated mucous lining of the trachea, bronchi, and bronchioles

Question 17

What is the role of the mucociliary escalator?

Answer 17

It sweeps foreign particles out of the lung

Question 18

What microbiota is found in the kidney and bladder?

Answer 18

It is normally sterile

Question 19

What is the bacterial makeup of the vagina?

Answer 19

It is weakly acidic and contains significant amounts of glycogen

Question 20

What resident organism of the vagina involves glycogen?

Answer 20

Lactobacillus acidophilus

Question 21

How does the vagina maintain acidity?

Answer 21

Lactobacillus acidophilus ferments glycogen to make lactic acid

Question 22

What is the pH of vagina?

Answer 22

roughly 5

Question 23

How does age change the microbiota and pH of the vagina?

Answer 23

Lactobacillus acidophilus is not present before puberty or after menopause and the pH at those times is neutral

Question 24

What commensal microbe is found in the vagina?

Answer 24

Yeasts like candida

Question 25

What is the state of information on male microbiota?

Answer 25

It is understudied

Question 26

What is the largest influence on penis microbiota and how does it affect it?

Answer 26

Circumcision was studied, and circumsized men after 6 months had fewer anaerobic bacteria

Question 27

What influences other than circumcision affect penis microbiota?

Answer 27

Age and sexual activity

Question 28

What microbiota is resembled by the penis?

Answer 28

Gut microbiota

Question 29

Do male and female partners share microbiota?

Answer 29

Yes (esp if uncircumcised)

Question 30

What is the pH of the gastrointestinal system?

Answer 30

Acidic (2) in the stomach, then less so in the small intestine (5 ish) and then neutral in the large (7)

Question 31

What are the bacteria compositions of most people?

Answer 31

Mostly Firmicutes, Mostly Bacteroidetes, or a mix of the two

Question 32

What are the three major phyla of human gut bacteria?

Answer 32

1. Firmicutes 2. Bacteroidetes 3. Proteobacteria

Question 33

What is the species level diversity of the human gut?

Answer 33

200-1000 per individual, but 3500-35000 total

Question 34

How much of the gut biome do archaea, fungi, yeasts, or protists form?

Answer 34

Very little

Question 35

What are 4 roles of the human gut biome?

Answer 35

1. Energy source 2. Physiological barrier 3. Metabolite production 4. Xenobiotic metabolism

Question 36

When do microbiota begin to accumulate in the body? How is this obtained?

Answer 36

Before birth, through the placenta which is said to have its own microbiome

Question 37

When is the first major introduction to microbes in a baby's life?

Answer 37

The birth canal and outside world

Question 38

What do early colonizing bacteria do in a baby and what is its physical makeup?

Answer 38

They are a source of vitamins and tend to be facultative anaerobes

Question 39

How old are people when they have adult microbiota composition?

Answer 39

3 years old

Question 40

What are the classifications of pathogens?

Answer 40

Primary pathogens - can cause disease in health hosts opportunistic pathogens - can cause disease only in compromised hosts or unwanted parts of the body

Question 41

What does infection mean?

Answer 41

Only the entering and growth of a pathogen in a host

Question 42

What term refers to the ability of an organism to cause disease?

Answer 42

Pathogenicity

Question 43

How is pathogenicity defined (3)?

Answer 43

1. Infectivity - ability to cause disease 2. Virulence - severity of disease 3. Genetic makeup

Question 44

How is virulence measured?

Answer 44

Studies of the infectious dose (ID-50) and the lethal dose (LD-50)

Question 45

What does the 50 stand for in ID_50 and LD_50)?

Answer 45

1. The number of cells that causes infection of 50% of hosts 2. The amount of agent that kills 50% of hosts

Question 46

What 6 events need to happen in order for infection to turn into symptoms? Which ones are infection process and which ones are disease process?

Answer 46

Infection process 1. Exposure 2. Adherence 3. Invasion 4. Multiplication Disease Process 5. Toxicity/invasiveness 2 6. Tissue/systemic damage

Question 47

What 5 portals of entry do bacteria take into the human body?

Answer 47

1. Mouth 2. Respiratory tract 3. Conjunctiva and mucous membranes 4. Wounds, injuries, lesions 5. Parental - straight blood contact

Question 48

What are the three roles of virulence factors?

Answer 48

1. Attach better 2. Avoid immune response 3. Destroy more to obtain nutrients

Question 49

What codes for a virulence factor?

Answer 49

A virulence gene

Question 50

What parts of a bacteria would aid in the attachment portion of infection?

Answer 50

Adhesins, capsules, fimbriae, pili, flagella

Question 51

What virulence adaptations are involved with tissue damage/colonization?

Answer 51

Proteases/nucleases (streptokinase, coagulase) Damage: endo/exotoxins, superantigens, others

Question 52

What is the tissue destroying enzyme?

Answer 52

Hyaluronidase

Question 53

What are the roles of coagulase and streptokinase?

Answer 53

Coagulase - clot forming streptokinase - clot breaking

Question 54

Why would a bacterium want to clot blood?

Answer 54

To prevent immune cells from reaching the infected site

Question 55

What are the two main types of bacterial toxins?

Answer 55

Exotoxins - bacterial protein that kills cells Endo toxins - LPS part that hyperactivates immune system

Question 56

What are the three typical examples of exotoxins?

Answer 56

AB toxins, cytolysins, and superantigens

Question 57

What are the differences in composition and source of endo and exo-toxins?

Answer 57

Exo - proteins from gram positive (primarily) Endo - Lipid A from gram negative

Question 58

What are the differences in effect, heat stability, and LD_50 of endo and exo-toxins?

Answer 58

Exo - damage to cells, some are heat liable, Low LD_50 Endo - inflammation/fever, Heat stable, and high LD50

Question 59

What are the 8 categories of microbial exotoxin?

Answer 59

1. Plasma membrane destruction 2. Cytoskeleton alteration 3. Protein synthesis disruption 4. Cell cycle disruption 5. Signal transduction disruption 6. Cell-cell adherence 7. Vesicular traffic 8. inhibit exocytosis PCPCSCVI

Question 60

How do membrane disruption exotoxins work?

Answer 60

They can act as membrane channels

Question 61

How do protein synthesis disruption proteins work?

Answer 61

They damage ribosomes

Question 62

How do signal disrupting exotoxins work?

Answer 62

They can plug transport protins

Question 63

What are the three types of exotoxins that break stuff down?

Answer 63

Phospholipase enzymes - break down phospholipids Hemolysins - blood cells (sometimes others) Leukocidins - lyse white blood cells cytolysins- form pores in membranes leading to cell death

Question 64

How do neurological exotoxins work?

Answer 64

Botulinum - seals release of Acetylcholine - no movement Tetanus toxin - prevents release of (inhibitory) GABA and glycine - spasms

Question 65

What is the makeup of an LPS unit?

Answer 65

Lipid a, core glycolipid, and O antigen

Question 66

How are endotoxins released?

Answer 66

Cell death releases

Question 67

What type of cell is an endotoxin? What does it bind to?

Answer 67

MAMP - microbe associated molecular pattern molecule that binds to macrophages + B cells

Question 68

What does endotoxin receptor binding trigger?

Answer 68

Cytokine release that can lead to inflammation, fever, shock, death

Question 69

What does pyogenic mean?

Answer 69

Makes pus

Question 70

Why can different strains of the same species cause different diseases?

Answer 70

They may differ in their method of disease causing (exotoxin release vs pyogenicity), or what virulence factor/type of toxin they utilize