intro to microbial infection

Question 1

4 barriers to entry of the immune system

Answer 1

normal microbiota
physical barriers
chemical barriers
phagocytes

Question 2

what is the normal microbiota?

Answer 2

this is the microorganisms that reside in the tissue and skin

Question 3

what does the microbiota do?

Answer 3

• they offer protection by competing with pathogens
• they produce antibiotic substances
• they produce toxic metabolic products
• may alter pH

Question 4

what will the normal microbiota be suppressed by?

Answer 4

antibiotics

Question 5

what are the examples of physical barriers?

Answer 5

skin - secretes sebum and fatty acids that inhibit growth
mucus clearance
flushing - pee, tears, sweat
peristalsis - moves waste out of the body preventing biofilms forming.

Question 6

what are examples of chemical barriers?

Answer 6

mucus
antimicrobial proteins
gastric acid
plasma proteins

Question 7

what is bacterial growth and survival dependant on?

Answer 7

upon the ability of an organism to sense its environmental conditions and respond to external stimuli

Question 8

what are the 2 ways infection happens?

Answer 8

invading host tissue
exerting effects from mucosal surface

Question 9

when does an infection occur

Answer 9

when a microorganism causes ill health

Question 10

what is disease?

Answer 10

the damage to cells, tissues and organs that causes dysfunction

Question 11

what are the 6 things that may cause disease?

Answer 11

• bacterial
  fungal
  viral
  protist
  macro parasite
  prion

Question 12

commensal

Answer 12

a micro organism that forms part of the hosts normal microbiota

Question 13

pathogen

Answer 13

an organism that causes disease

Question 14

pathogenicity

Answer 14

the capacity to cause disease

Question 15

pathogenesis

Answer 15

the development of disease

Question 16

virulence

Answer 16

a measure of the capacity to cause disease

Question 17

what are the 3 types of pathogen?

Answer 17

obligate pathogen = almost always associated with disease
conditional pathogen = may cause disease if certain conditions are met
opportunistic pathogen = usually only effects an immune compromised host

Question 18

what are the 6 steps in infection?

Answer 18

1- recognition
2- attachment and entry
3- multiplication
4- evasion of host defences
5/6- shedding and damage

Question 19

what are the 4 ways infection can be established in a healthy host?

Answer 19

1- microbes with mechanisms for attachment and penetration
2- microbes introduced to host by biting arthropods
3- microbes introduced to host via skin wounds
4- microbes only able to infect when host defences are impaired

Question 20

what is tissue tropism?

Answer 20

the affinity of the microbe for a specific tissue
defines the tissue that supports the growth of the microbe

Question 21

do all microbes have the same tropism?

Answer 21

no, some have a broad range of cells and tissues they will infect, others can be very specific.

Question 22

what are the influencing factors for tissue tropism?

Answer 22

• presence of cell receptors
• transcription factors
• temp
• physical barriers
• ph

Question 23

what cell will varicella zoster virus infect?

Answer 23

nerve cells

Question 24

what cells will HBV infect

Answer 24

liver cells

Question 25

what cells will helicobacter pylori infect?

Answer 25

gastric mucosa

Question 26

what cells will HIV infect

Answer 26

t lymphocytes

Question 27

what cells will neisseria meningitides infect?

Answer 27

nasopharyngeal epithelium

Question 28

where will the influenza virus attach?

Answer 28

to cilia and microvilli on the tracheal epithelium

Question 29

what cells will the vibrio cholerae infect?

Answer 29

villi of intestinal epithelium

Question 30

what are the factors that favour good virulence?

Answer 30

• toxin secretion (bacteria and fungi)
• antibiotic resistance
• pilus formation
• capsule
• iron transport systems
• adhesion factors
• enzymes

Question 31

describe endotoxins

Answer 31

• low toxicity
• part of the cell wall of gram negative
• low specificity
• found in lipopolysaccharide area

Question 32

describe exotoxins

Answer 32

• highly toxic
• secreted from bacterial cells
• produced by gram positive and negative
• can be converted into toxoids for vaccine use

Question 33

what are the factors that favour antibiotic resistance for a microbe?

Answer 33

• resistance genes on plasmids
• production of enzymes
• impermeability
• efflux mechanisms
• alteration of target site

Question 34

what 3 factors does transmission depends on?

Answer 34

1- the number of micro organisms shed
2- the number of micro organisms required to infect
3- the micro organisms stability in the environment

Question 35

fomite transmission

Answer 35

via an inanimate object

Question 36

what are the 2 types of vectors in animal to human transmission

Answer 36

invertebrate vectors - arthropods and shellfish
vertebrates - mammals and birds