bacteria as causes of diseases

Question 1

what is a pathogen?

Answer 1

Organism that causes or is capable of causing disease

Question 2

what is a commensal?

Answer 2

Organism which colonises the host but causes no disease in normal circumstances

Question 3

what is an opportunist pathogen?

Answer 3

Microbe that only causes disease if host defences are compromised

Question 4

what is virulence/ pathogenicity?

Answer 4

The degree to which a given organism is pathogenic

Question 5

what is asymptomatic carriage?

Answer 5

When a pathogen is carried harmlessly at a tissue site where it causes no disease

Question 6

in bacterial morphology what is the gram stain ?

Answer 6

positive- purple ( double cell membrane

Question 7

in bacterial morphology what is the bacteria ?

Answer 7

stain pink= negative

Question 8

what are protists?

Answer 8

larger microbes

Question 9

describe the membrane of gram negative bacteria

Answer 9

2 membranes
an inner and outer membrane
separated by lipoprotein, preiplasmic space and peptidogyclan

Question 10

what are the two membranes in gram negative bacteria separated by?

Answer 10

separated by lipoprotein, periplasmic space and peptidoglycan

Question 11

what are areas open to bacterial colonisation called?

Answer 11

mucosal surfaces

Question 12

what are the two bacterial toxins?

Answer 12

endotoxin
exotoxin

Question 13

describe endotoxin

Answer 13

component of the outer membrane of bacteria, e.g. lipopolysaccharide in gram negative bacteria

Question 14

describe the nucleus of bacteria

Answer 14

doesn’t have one
naked
dna transcribed in cytoplasm

Question 15

describe exotoxin

Answer 15

secreted proteins of gram positive and gram negative bacteria that causes damage to host cell

Question 16

what are the two ways there is genetic variation in bacteria?

Answer 16

mutation
gene transfer

Question 17

how do mutations increase genetic variation in bacteria?

Answer 17

base substitution
deletion
transfer

Question 18

how does gene transfer increase genetic variation in bacteria?

Answer 18

Transformation e.g. plasmid
Transduction e.g. via phage
Conjugation e.g. via sex pilus

Question 19

what are the 4 steps of preparing a gram stain?

Answer 19

1. Apply a primary stain such as crystal violet (purple) to heat fixed bacteria
2. Add iodide which binds to crystal violet and helps fix it to the cell wall
3. Decolourise with ethanol or acetone
4. Counterstain with safranin (pink)

Question 20

what is the environment bacteria can survive in?

Answer 20

Temperature
<-800C to + 80C (1200C for spores)
pH
<4-9
Water/dessication
2 hours – 3 months (>50 years for spores)
Light
UV

Question 21

what is exotoxin made up of?

Answer 21

protein

Question 22

what is endotoxin made up of?

Answer 22

lipopolysacccharide

Question 23

what is the action of exotoxin

Answer 23

specific

Question 24

what is the action of endotoxin?

Answer 24

non- specific

Question 25

what is the effect of heat on exotoxin?

Answer 25

labile

Question 26

what is the effect of heat on endotoxin?

Answer 26

stable

Question 27

what is the antigenicity of exotoxin?

Answer 27

strong

Question 28

what is the antigenicity of endootoxin?

Answer 28

weak

Question 29

can exotoxin or endotoxin be converted to toxoid?

Answer 29

exotoxin can endotoxin can't

Question 30

what does the bacterial chromosome contain?

Answer 30

2-4 x 10^3 kb

Question 31

what do plasmids do and contain?

Answer 31

transfer promotion genes contain plasmid maintenance genes contain antibiotic or virulence dominant genes

Question 32

what does the coagulase test do?

Answer 32

Distinguishes S.aureus from other staphylococci – coagulase positive

Question 33

what are the two main groups of classification of bacteria?

Answer 33

OBLIGATE INTRACELLULAR BACTERIA or BACTERIA THAT MAY BE CULTURED ON ARTIFICIAL MEDIA

Question 34

describe obligate intracellular bacteria

Answer 34

grow inside cells can't culture normally

Question 35

what are the two main categories of bacteria that may be cultured on artificial media?

Answer 35

WITH A CELL WALL or WITHOUT CELL WALL ( can be remembered using mollicutes)

Question 36

what are the two categories for those with a cell wall?

Answer 36

GROWING AS SINGLE CELLS or GROWING AS FILAMENTS

Question 37

What does the oxidate test test for?

Answer 37

Tests if micro-organism contains a cytochrome oxidase – implies organism able to use oxygen as the terminal electron acceptor

Question 38

what are the three types of haemolysis?

Answer 38

alpha beta gamma

Question 39

describe alpha haemolysis

Answer 39

haemolysis causing by production of hydrogen peroxide oxidising haemoglobin – the agar appears green

Question 40

describe beta haemolysis

Answer 40

haemolysis results because of lysis of red blood cells by haemolysis such as Streptolysin O produced by S.pyogenes

Question 41

describe gamma haemolysis

Answer 41

haemolysis implies no haemolysis