bacterial pathogensis

Question 1

What are pathogens

Answer 1

Disease casing bacteria affecting all with normal host defences

Question 2

What are non-pathogenic pathogens

Answer 2

Organisms that invade an individual without causing any obvious detectable symptoms

Question 3

What are asymptomatic infections caused by

Answer 3

Microbes

Question 4

Till when can organisms remain latent (dormant/inactive form)

Answer 4

Until they are reactivated with the recurrence of symptoms

Question 5

What are the 3 consequences of antibiotic use in the alteration of normal gut flora

Answer 5

Sensitive gut flora killed => overgrowth with resistance => C. Difficile toxin production => diarrhoea and pseudomembranous colitis

Question 6

What are the treatment options for affected normal gut flora from the use of antibiotics

Answer 6

-stop prescribing antibiotic
-oral metronidazole or vancomycin
-recovery requires reestablishment of normal flora

Question 7

What is the first Koch’s postulates

Answer 7

1)the pathogen must be present in every case of the disease

Question 8

What is the second Koch’s postulates

Answer 8

2)the pathogen must be isolated from the diseased host and grown in a pure culture

Question 9

What is the third Koch’s postulates

Answer 9

3)the specific disease must be reproduced when a pure culture of the pathogen is inoculated into a healthy susceptible host

Question 10

What is the fourth Koch’s postulates

Answer 10

4)the pathogen must be recoverable from the experimentally infected host

Question 11

What are methods for the transmission of pathogens

Answer 11

Oral - oral
Feces - oral
Blood - blood
Sexual - contact

Question 12

How is iron fundamental in infection

Answer 12

Without iron bacteria cannot power themselves to be pathogenic

Question 13

What are 7 microbial pathogenicity factors

Answer 13

-toxins
-iron uptake
-adhesions
-LPS
-invasins
-slime
-enzymes

Question 14

When does the first invasion occur for commensal microbes

Answer 14

When they breach the mucosal layer and eating + using nutrients from cells to produce factors and allow for pathogenicity

Question 15

What are characteristics of flagellae

Answer 15

-multi-subunit structures
-mono or poly-trichous

Question 16

How does flagellae help in reaching site of infection

Answer 16

Facilitates propulsion (propelling) to specific host targets

Question 17

What is flagellae recognised by

Answer 17

By the innate immune system as PAMP recognised by TLR5

Question 18

What are characteristics of frimbriae

Answer 18

-hair like surface structures
-consist of various protein subunits

Question 19

What are the types of bacterial adhesion

Answer 19

-flagellae of gram-negative bacteria
-fimbriae and pili of gram-negative bacteria

Question 20

What do fimbriae interact with

Answer 20

Eukaryotic cells or inert surfaces via receptors at the tip

Question 21

What do many fimbriae receptors recognise

Answer 21

Sugars

Question 22

What are characteristics of pili

Answer 22

-structurally similar to fimbriae
-longer than fimbriae
-mostly only one present on surface

Question 23

What are pili involved in

Answer 23

In the conjugation (f-pili) or serve as receptors for phages

Question 24

Why is adhesion important for bacteria to host cells

Answer 24

-prevents bacteria from being washed off by fluid flow
-formation of a micro colony
-relevance to pathogenicity

Question 25

What do adhesins cause

Answer 25

Bacteria adhesion to host cell, formation of colonies and biofilms

Question 26

What do toxins do

Answer 26

Cause the destruction of tissue

Question 27

What do invasins do

Answer 27

Invasion and multiplication of bacteria

Question 28

What are the different type of toxins produced from bacteria

Answer 28

Exotoxins Endotoxin Enterotoxin

Question 29

What are exotoxins

Answer 29

Any toxin that is actively secreted by a bacterium in the environment or supernatant

Question 30

What is an endotoxin

Answer 30

A synonym for the LPS of gram-negative bacteria - only associated with gram -ive bacteria (cell-surface bound)

Question 31

What is an enterotoxin

Answer 31

An exotoxin that is effective in the gastrointestinal tract

Question 32

What is the mode of action of botulinum toxin (Botox toxin) (exotoxins)

Answer 32

-botulinum toxin acts at the end of motor end plate to prevent release of acetylcholine from vesicles -results in lack of stimulus to muscle fibres -irreversible relaxation of muscle and flaccid paralysis

Question 33

What is the mode of action of tetanus toxin (exotoxins)

Answer 33

-tetanus toxin binds to interneuron to prevent release of glycine from vesicles -result in lack of inhibitory signals to motor neurons -constant release of acetylcholine to muscle fibres -irreversible contraction of muscles and spastic paralysis

Question 34

What are invasin factors

Answer 34

Protease Glycosidases Nucleases Lipases

Question 35

How do the invasive factors lytic toxins damage membranes enzymatically and physically

Answer 35

Enzymatically - phospholipases Physical - membrane-insertion

Question 36

How do invasins cause damage enzymatically

Answer 36

Produced as enzymes and degrade enzymatic pathways

Question 37

How do invasins cause damage physically

Answer 37

Invasins physically inserted into eukaryotic cell membranes to then bind to cholesterol or non-cholesterol structures

Question 38

What produces iron binding compounds

Answer 38

Siderophores

Question 39

What does a greater production of sidephores result in

Answer 39

The microbe being more virulent and pathogenic

Question 40

What are defensive pathogenic factors from the host defence mechanism

Answer 40

-polysaccharide capsule:negatively charged -slime -biofilm

Question 41

What are defensive pathogenic factors from the host immunogenic mechanism

Answer 41

-LPS:cytokines overstimulation -> leads to septic shock -outer membrane proteins (OMPs): inactivate anti microbial peptides or complement factors