13. Bacteria-host interactions

Question 1

What kind of microbe-host interactions do we have

Answer 1

Contamination
Colonization
Infection

Question 2

What’s contamination

Answer 2

The host encounters the mo when it reaches the skin or mucosal sirfaces

Question 3

What’s colonization

Answer 3

Mo finds ideal conditions for its settlement in a specific host district and starts proliferation( cell growth and division)

Question 4

Is presence of mo in host district immediately an infection or a disease

Answer 4

No

Question 5

What’s infection

Answer 5

Mo in specific district establishes a balanced relationship with the host defenses

Question 6

Does infection leave sign on host’s immune system

Answer 6

Yes

Question 7

What are districts in a human body where we shouldn’t find mo and finding them indicates severe infectious disease

Answer 7

Blood, internal organs, lymphatic system and nervous system

Question 8

What are colonized districts of the human body

Answer 8

Skin and mucous membranes

Question 9

How does normal microbic flora get to the organism

Answer 9

All organisms are sterile in utero. After birth, skin and many mucous membranes become rapidly colonized by non pathogenic microbes(normal microbic flora, microbiota)

Question 10

Are microbiota beneficial

Answer 10

Yes, and they don’t cause diseases. They can participate in synthesis of vitamins and protection from pathogenic bacteria

Question 11

What are some examples of microbiota?

Answer 11

Lactobacillus spp.; Bacteroides spp.; viridans streptococci, enterobacteriales and Candida spp.

Question 12

What factors are impacting the change of endogenous microflora

Answer 12

Age, gender( hormonal state), diet, health state, drugs

Question 13

What type of colonization can we have

Answer 13

Transient and chronic

Question 14

What’s disease

Answer 14

Interaction that leads to harmful pathogenic process

Question 15

What does disease depend on

Answer 15

Microbial factors
Host immune response against mo
Host genetic factors

Question 16

What is pathogenicity

Answer 16

Ability of mo to cause a disease

Question 17

What does pathogenic potential depend on

Answer 17

Virulence factors and mechanism(mo related)
Initial inoculum(initial number of infecting bacteria
Immune status and health conditions of the host( host related)

Question 18

What’s virulence

Answer 18

Degree of which a pathogenic organism can cause a disease

Question 19

What does virulence depend on

Answer 19

Infectivity: ability to establish an initial infectious outbreak
Invasivity: ability to spread to other host tissues escaping the host defense mechanisms
Toxinogenicity: ability to produce toxins

Question 20

What are nonpathological bacteria

Answer 20

Bacteria that don’t cause infection in humans

Question 21

What are pathogenic bacteria

Answer 21

Bacterial species that are always pathogenic and their simple presence indicates a pathological process

Question 22

Do pathogenic bacteria abide by Koch’s postulates

Answer 22

Yes

Question 23

What are opportunistic pathogenic bacteria

Answer 23

Bacterial species that constitute the normal microbic flora in humans and animals and can cause diseases only in immunodepressed or debilitated subjects

Question 24

What are occasional pathogenic bacteria

Answer 24

Bacterial species that don’t usually interact with the host, but whenever they are innoculated in host tissues they can cause disease

Question 25

When do opportunistic bacteria become pathogenic

Answer 25

When:
1. They change host district( ex: E.coli can cause urinary tract infectious)
2. Habitat is altered
3. Immature/ decline of host defenses

Question 26

What is successful pathogenic microbe

Answer 26

Microbe that can adopt specific counteracting strategies to overcome host defense barriers

Question 27

What are portals of entry for mo

Answer 27

Mucous membranes, skin, parenteral route, endogenous infections

Question 28

What is colonization a result of

Answer 28

Virulence mechanism that make microbe able to:
-Adhere to the host cells and tissues
-Invade the host tissues
-Resist the innate immunity
-Escape adaptive immunity
-Compete for nutrients

Question 29

What are the steps of bacterial pathogenic process

Answer 29

1.Exposure
2.Adhesion
3.Colonization
4.Invasion
5.Proliferation
6. Tissue damage due to proliferation and alteration of host’s physiological functions
7.Host-mediated immunopathogenesis

Question 30

What are exotoxins

Answer 30

Proteins that can be found both in gram+ and Gram - bacteria. They are released by cell in exponential growth and have different mechanism of action and effects.

Question 31

When are exotoxins endowed activity

Answer 31

At very low concentrations

Question 32

What can exotoxins target

Answer 32

Cell surface and intracellular components

Question 33

What are endotoxins

Answer 33

Lipid portion that are part of outer membrane in Gram - bacteria. they are liberated when bacteria dies and the cell wall breaks apart

Question 34

What components can be endotoxins

Answer 34

-LPS-lipopolysaccharide
-portions of peptidoglycan with endotoxin-like activity
-lipoteichoic acid( even if its from Gram +)
-other components of cell wall lining

Question 35

Can proteins and enzymes be endotoxins

Answer 35

No

Question 36

What do endotoxins do

Answer 36

Trigger nonspecific inflammatory reactions;
stimulate pro-inflammatory cytokine release;
induce complement activation;
stimulate proliferation of B lymphocytes and antibody production
induce fever

Question 37

What is relationship between vaccines and endotoxins

Answer 37

Endotoxins act as adjuvant for vaccines
Adjuvant= substance that enhances body’s immune response to antigen

Question 38

What are some mechanism by which pathogens evade immune response

Answer 38

-Inhibition or resistance to phagocytosis
-Degradation/inhibition of immune components: pathogens can degrade immune components( such as antibodies or complement proteins). Proteases break down these molecules, impairing immune function
-Antigenic mimicry :pathogens may host molecules to avoid detection. Strategies include:
*capsules : coating themselves with protective layer
*surface proteins : displaying proteins similar to host proteins
*binding to host proteins