Bacterial colonization, tissue invasion and clinical disease

Question 1

A number of bacterial species can reside in animal hosts, either as?

Answer 1

commensals or as potential pathogens

Question 2

are host to an enormous number of resident microbes

Answer 2

Mammals

Question 3

can interact with host tissues in ways that result in disease

Answer 3

Pathogenic bacteria

Question 4

What are commensals?

Answer 4

-Commensal organisms, acquired soon after birth, are able to adhere to body surfaces.

Question 5

Commensal organisms form stable polymicrobial communities that are present throughout life as ___________
on the skin and in the hollow organs surfaces and cavities are open to the environment.

Answer 5

normal microflora

Question 6

the composition of the microbial communities tends to be?

Answer 6

• host specific
• within hosts
• organ specific

Question 7

it is beneficial to the host in many ways

Answer 7

stable microflora

Question 8

it relies on the normal microflora to drgrade ingested material in the rumen of cattle and sheep, in the caecum and colon of horses, and in the colon of pigs.

Answer 8

digestive system

Question 9

normal microflora degrade ingested material in the?

Answer 9

✓ rumen of cattle and sheep
✓ caecum and colon of horses
✓ colon of pigs

Question 10

what vitamins does microflora of the rumen synthesizes?

Answer 10

Vitamin K and Vitamin B

Question 11

what body system does normal microflora primes?

Answer 11

immune system

Question 12

When the community of commensals occupying a particular niche is in ecological balance, the bacteria utilize the resources they require from the host without causing any obvious adverse effects

Question 13

When an equilibrium is disturbed or when the host is under severe stress, an indigenous member may escape from the restraining influences of the bacterial community and act as an?

Answer 13

opportunistic pathogen

Question 14

Opportunistic pathogen occur in?

Answer 14

gastrointestinal tract following the administration of oral antibiotics

Question 15

bacteria that can exist as a commensal in the rumen

Answer 15

Fusobacterium necrophorum

Question 16

When Fusobacterium necrophorum transfer to the liver of feedlot cattle, what will happen?

Answer 16

it can act as a pathogen that causes HEPATIC ABSCESSES

Question 17

For a microbw to act as a pathogen;

Answer 17

✓ must find an appropriate niche within a host
✓ must compete with the normal microflora to gain a foothold in that niche
✓ must evade normal host defences
✓ must express the genes that encode the factors that cause disease

Question 18

the ability of a microbe to damage a host

Answer 18

pathogenecity

Question 19

the relative capacity of a pathogen to damage a host

Answer 19

virulence

Question 20

The bacterial traits that confer pathogenecity

Answer 20

virulence factors

Question 21

Virulence Factors;

Answer 21

✓ adhesins
✓ toxins
✓ capsules

Question 22

genes are expressed only when their products are required in a process

Answer 22

phase variation

Question 23

are not uniformly distributed among all the strains of a particular bacterium

Answer 23

Genes encoding virulence factors

Question 24

Genes that encode virulence factors are associated with a mobile genetic elements

Answer 24

bacteriophages, plasmids, and pathogenecity islands

Question 25

arise when bacteria that live on the skin or mucous membranes as harmless commensals take advantage of impaired antimicrobial defenses of the host and behave as opportunistic pathogens

Answer 25

endogenous infections

Question 26

Endogenous infections happens when?

Answer 26

- epithelial barriers are damaged - immunity is weakened by drugs, radiation or exogenous pathogens - ecological balance of the resident microbial community is disturbed by administration of antibiotics - bacteria gain access to sites from which they are usually absent

Question 27

occur after direct or indirect transmission from an infected animal or from the environment

Answer 27

Exogenous infections

Question 28

Pathogens may enter a host through?

Answer 28

skin, conjunctiva, umbilicus, teat canal, main portals of the mucosae, gastrointestinal, respiratory and urogenital

Question 29

determines the site of the initial interaction between pathogen and host and also the organs at greatest risk of infection

Answer 29

route of infection

Question 30

are driven by microbial genes that express virulence factors and by host genes that are responsible for resistance to pathogens

Answer 30

subsequent interactions

Question 31

in bacterial infections, the host may be damaged by BACTERIAL TOXINS, by the inflammatory response elicited by the bacteria or their toxins or commonly by both

Answer 31

toxins and inflammatory reactions

Question 32

Two categories of Pathogens that are able to survive within host cells

Answer 32

✓ strict (obligate) intracellular pathogens ✓ facultative intracellular pathogens

Question 33

2 obligate intracellular pathogens

Answer 33

Chlamydiae and rickettsiae

Question 34

What are the facultative intracellular pathogens?

Answer 34

✓ Mycobacterium- phagocytic cells ✓ Brucella- uropathogenic E. coli ✓ Salmonella ✓ Listeria monocytogenes- non-phagocytic epithelial cells

Question 35

play a significant role throughout the coarse of an infection

Answer 35

adhesins

Question 36

what is the use of adhesins in Pathogens?

Answer 36

attach to host tissues and to resist the flushing action of body fluids

Question 37

a transcription factor that moves to the cell nucleus where it up-regulates the expression of a number of pro-inflammatory genes

Answer 37

nuclear factor-kappaB

Question 38

resistant to phagocytic cells because of its large size

Answer 38

biofilm

Question 39

what is capsules?

Answer 39

help the bacterium to resist desiccation

Question 40

composed of polyglutamic acid; it is anti-phagocytic and is regarded as an essential virulence factor

Answer 40

Bacillus anthracis

Question 41

Two types of bacterial toxins

Answer 41

Exotoxins and Endotoxins

Question 42

produced and secreted by viable bacteria

Answer 42

exotoxins

Question 43

integral constituents of the bacterial cell wall not released until the microorganisms are lysed

Answer 43

endotoxins

Question 44

Endotoxin composed of three parts;

Answer 44

hydrophobic glycolipid (lipid A) hydrophilic polysaccharide Opolysaccharide (O antigen)

Question 45

released when bacterial cell walls are damaged by the complement system, phagocytes or antimicrobial drugs

Answer 45

Lipopolysaccharide

Question 46

toll-like receptor 4 (TLR-4)

Answer 46

mononuclear phagocytes, neutrophils, platelets, dendritic cells and B lymphocytes

Question 47

High concentrations of circulating endotoxin greatly increase the release of?

Answer 47

cytokines, interleukin-1, tumor necrosis factor-alpha

Question 48

stimulate the production of prostaglandins and leukotrienes which are mediators of inflammation

Answer 48

cytokines

Question 49

responsible for the deposition of thrombi in small vessels and for a dramatic drop in blood pressure, giving rise to life-threatening endotoxic shock

Answer 49

Lipopolysaccharide (LPS)

Question 50

categories of exotoxins

Answer 50

✓ toxins that act on the extracellular matrix ✓ toxins that act on the plasma membrane of their target cells ✓ toxins that act inside the cells ✓ toxins that cause dysfunction of the immune system

Question 51

toxins that cause dysfunction of the immune system

Answer 51

superantigens