lecture 5) clinical microbiology 1

Question 1

name 4 requirements for a disease

Answer 1

portal of entry
avoid host defences
establishment
damages host

Question 2

what is characteristic about the main portals of entry?

Answer 2

they are lined with mucous membranes

Question 3

what is mucuous and what is its importance?

Answer 3

liquid solution
composed of glycoproteins
retains moisture

Question 4

what are mucous membranes protected with?

Answer 4

hair
skin
washing secretions
cilia

Question 5

what are the main roles of mucous membranes?

Answer 5

protective covering
resists penetration
traps microbes

Question 6

what are mucous membranes bathed in?

Answer 6

antimicrobial secretions

Question 7

what is the main enzyme in antimicrobial secretions?

Answer 7

lysozyme

Question 8

what type of bacteria is lysozyme?

Answer 8

gram positive

Question 9

what does lysozyme do?

Answer 9

breaks glycosidic bonds in peptidoglycan

Question 10

mucous contains MALT. what is MALT?

Answer 10

mucosal associated lymphoid tissue

Question 11

what are the primary lymph organs?

Answer 11

bone marrow

thymus

Question 12

what are the secondary lymph organs?

Answer 12

MALT

lymph nodes

Question 13

many body fluids are not suitable for bacterial growth. why is this?

Answer 13

makes it inhospitable for the pathogen so it cannot cause infection

Question 14

what is the importance of iron?

Answer 14

everything needs iron to live

Question 15

how do bacteria gain iron from the host?

Answer 15

secrete siderophores
rip off iron and hold it
when this happens the skin becomes slightly acidic

Question 16

what is the bacterial growth inhibitor found in breast milk?

Answer 16

lactenin

Question 17

what makes lactenin a bacterial growth inhibitor?

Answer 17

it is selectively bactericidal

Question 18

what are antimicrobial peptides?

Answer 18

peptide produced by bacteria that are lethal to closely related bacterial species

Question 19

what do antimicrobial peptides do?

Answer 19

produced by bacteria
destroy the membrane
tamper with DNA and RNA

Question 20

what makes antimicrobial peptides so selective?

Answer 20

always carry more of a negative charge on their membranes that eukaryotic cells
creates an electrostatic attraction

Question 21

describe the antimicrobial peptide sakacin

Answer 21

produced by lactobacilli (eg liseria, gram positive)

some have been engineered for mass food production

Question 22

describe the antimicrobial peptide colicin

Answer 22

produced by E.coli
used in polymixin antibiotics
LAST resort of antibiotics as they cause terrible collateral damage

Question 23

names the defensins of the respiratory tract

Answer 23

beta defensins

Question 24

give an example of a beta defensin found in the respiratory tract

Answer 24

cathelicidin

Question 25

what are defensins?

Answer 25

cysteine rich cationic proteins that act as defensive proteins

Question 26

what is cathecilidin also known as?

Answer 26

LL37

Question 27

what cells produce cathecilidin?

Answer 27

neutrophils | epithelial cells

Question 28

what is the mode of function of cathecilidin as a beta defensin in the respiratory tract?

Answer 28

have an ampithatic structure (hydrophobic and hydrophillic regions) hydrophobic region interacts with lipids hydrophillic regions come together unordered structure becomes ordered which impacts pore formation

Question 29

what does the stomach secrete to make the pH 2?

Answer 29

gastric acid

Question 30

what bacteria has been found in the stomach to have links with causing stomach ulcers?

Answer 30

heliobacter pylori

Question 31

what do the intestines secrete?

Answer 31

IgA pancreatic enzymes bile GALT (gastrointestinal associated lymphoid tissue)

Question 32

what sort of movement is carried out by the intestines?

Answer 32

peristalsis

Question 33

where are the paneth cells found?

Answer 33

crypts of liberkun

Question 34

what enzyme do paneth cells secrete?

Answer 34

lysozyme

Question 35

what type of defensins are found in the GI tract?

Answer 35

alpha defensins

Question 36

what makes the alpha defensins in the GI tract different to the beta defensins in the respiratory tract?

Answer 36

open-ended argenine and cysteine residues 3 pairs of intramolecular disulphide bonds giving them a different secondary and tertiary structure

Question 37

what is the major difference between gram positive and gram negative bacteria?

Answer 37

gram negative have an outer phospholipid bilayer whereas gram positive bacteria have a thicket peptidoglycan cell wall

Question 38

what is present in gram positive bacteria that is a good vaccine target?

Answer 38

teichoic acid

Question 39

why is it good to have a good vaccine target?

Answer 39

antibiotic resistance is on the rise

Question 40

give 2 examples of gram positive bacteria that have teichoic acid

Answer 40

C. diff | S. aureus

Question 41

what was the first surface protein found in gram positive bacteria?

Answer 41

protein M

Question 42

what makes M protein a good target?

Answer 42

protrudes cell wall therefore good attachment

Question 43

give an example of a gram positive bacteria that has M proteins

Answer 43

Strep. pyogenes

Question 44

what acid in gram positive bacteria prevents the action of many antibiotics? give an example of a bacteria that has this acid

Answer 44

mycolic acid | TB

Question 45

what does lipid A do in gram negative bacteria?

Answer 45

anchors LPS

Question 46

if lipid A anchors the LPS, what happens?

Answer 46

heightened reaction

Question 47

what type of toxin is lipid A?

Answer 47

endotoxin

Question 48

what antigen is found in gram negative bacteria that is very variable, used in typing and that is recognised by the immune system?

Answer 48

O antigen

Question 49

what is the name for a structure found in gram negative bacterial cell walls that is composed of polysaccharised and proteins?

Answer 49

glycocalyx

Question 50

what is the importance of glycocalyx in the cell wall of gram negative bacteria?

Answer 50

creates a loose slime layer | highly organised - can make capsules so the bacteria can avoid the host's immune cells

Question 51

where are flagella and axial filaments found in gram negative bacteria?

Answer 51

beyond the cell wall

Question 52

what is the function of flagella and axial filaments?

Answer 52

aids movement

Question 53

name an alternative to flagella that are shorted in length

Answer 53

fimbrae and pili

Question 54

name a mechanism that the fimbrae and pii use for immune evasion?

Answer 54

antigenic variation | change protein in pili

Question 55

what is DNA's contribution to antibiotic resistance?

Answer 55

it has caused it to spread as it has replicated the genes that have evolved to be resistant to antibiotics

Question 56

components of bacterial cell walls can be targets for what?

Answer 56

therapeutics

Question 57

what can ribosomes be targets for in bacterial cells?

Answer 57

antibiotics

Question 58

what damage do neurotoxins cause?

Answer 58

damage to nervous system cause paralysis eg. tetnus lock jaw

Question 59

what impacts to enterotoxins cause in the host?

Answer 59

``` sickness and diarrhoea AB toxin (can be both) ```

Question 60

what impacts do cytotoxims have on the host?

Answer 60

cell death

Question 61

neurotoxins, enterotoxins and cytotoxins are all examples of what type of toxins?

Answer 61

exotoxins

Question 62

anthrax, diphtheria and vibrio are all examples of exotoxins. what is similar about them?

Answer 62

all gram positive most exotoxins are very bad news if you have an exotoxin that is gram negative

Question 63

are exo and endotoxins gram negative or positive?

Answer 63

``` endo = negative exo = positive ```

Question 64

where are exo and endotoxins found?

Answer 64

endotoxins found on the cell wall | exotoxins found extracellularly

Question 65

what are the structures of exo and endotoxins

Answer 65

``` exo = polypeptide endo = LPS complex ```

Question 66

which are more stable, exo or endotoxins?

Answer 66

endotoxins

Question 67

which are weaker, exo or endotoxins?

Answer 67

endotoxins are weaker therefore have a larger lethal dose

Question 68

what do endotoxins cause in the host?

Answer 68

fever

Question 69

which are more specific, exo or endotoxins?

Answer 69

``` exo = specific endo = non-specific ```

Question 70

name 2 compounds that streptococcus bacteria have to avoid the host's defences?

Answer 70

coagulase | leukocidens

Question 71

what do leukocidens kill?

Answer 71

white blood cells

Question 72

what type of toxin are leukocidens?

Answer 72

cytotoxins

Question 73

what group of bacteria produce leukocidens?

Answer 73

staph and strep

Question 74

what does coagluse do?

Answer 74

causes fibrin blood clots in host

Question 75

what makes strep more virulent than staph?

Answer 75

strep produces coagulase

Question 76

what is the impact of antibiotics on gut microbiota?

Answer 76

antibiotics disturb the gut microbiota

Question 77

if the gut microbiota is disturbed when using antibiotics to treat C.diff, what is the outcome?

Answer 77

diarrhoea

Question 78

what makes a pathogen established in a host?

Answer 78

surface of the bug interacts with the host

Question 79

what nearly always causing adhesion of the bug to the host?

Answer 79

proteins or carbohydrates or both (glycoproteins)

Question 80

name a structure in bacteria that helps with adhesion

Answer 80

pili

Question 81

what do pili do to help adhesion?

Answer 81

help bacteria attach and penetrate as they attach to receptors on the host's surface

Question 82

how do pili retract and what impact does this have on the bacteria when they are trying to establish themselves in the host?

Answer 82

retract via motors | bring bacteria closer to the host